GERDAU S.A. (SEC Filing Page | XBRL Cloud Viewer | XBRL Instance)

Line Label Object Class Period Type Balance Report ElementName
1 00090 - Document - Document and Entity Information Network

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 http://www.gerdau.com/role/DocumentDocumentAndEntityInformation
2 Implied Table Table

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3 Document - Document and Entity Information Abstract ggb:DocumentAndEntityInformationAbstract
4 Entity Registrant Name Concept (Text/String) For Period dei:EntityRegistrantName
5 Entity Central Index Key Concept (CIK Number) For Period dei:EntityCentralIndexKey
6 Document Type Concept (Submission Type) For Period dei:DocumentType
7 Document Period End Date Concept (Date) For Period dei:DocumentPeriodEndDate
8 Amendment Flag Concept (Yes/No) For Period dei:AmendmentFlag
9 Current Fiscal Year End Date Concept (Month/Day) For Period dei:CurrentFiscalYearEndDate
10 Entity Well-known Seasoned Issuer Concept (Yes/No) For Period dei:EntityWellKnownSeasonedIssuer
11 Entity Voluntary Filers Concept (Yes/No) For Period dei:EntityVoluntaryFilers
12 Entity Current Reporting Status Concept (Yes/No) For Period dei:EntityCurrentReportingStatus
13 Entity Filer Category Concept (Filer Category) For Period dei:EntityFilerCategory
14 Entity Emerging Growth Company Concept (Yes/No) For Period dei:EntityEmergingGrowthCompany
15 Entity Shell Company Concept (Yes/No) For Period dei:EntityShellCompany
16 Entity Common Stock, Shares Outstanding Concept (Shares) As Of dei:EntityCommonStockSharesOutstanding
17 Document Fiscal Year Focus Concept (Year) For Period dei:DocumentFiscalYearFocus
18 Document Fiscal Period Focus Concept (Fiscal Period) For Period dei:DocumentFiscalPeriodFocus
19 00100 - Statement - CONSOLIDATED BALANCE SHEETS Network

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 http://www.gerdau.com/role/StatementConsolidatedBalanceSheets
20 Implied Table Table

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21 CONSOLIDATED BALANCE SHEETS Abstract ifrs-full:StatementOfFinancialPositionAbstract
22 ASSETS Abstract ifrs-full:AssetsAbstract
23 CURRENT ASSETS Abstract ifrs-full:CurrentAssetsAbstract
24 Cash and cash equivalents Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
25 Short-term investments Concept (Monetary) As Of Debit ifrs-full:ShorttermDepositsNotClassifiedAsCashEquivalents
26 Trade account receivable - net Concept (Monetary) As Of Debit ifrs-full:CurrentTradeReceivables
27 Inventories Concept (Monetary) As Of Debit ifrs-full:Inventories
28 Tax credits Concept (Monetary) As Of Debit ifrs-full:CurrentReceivablesFromTaxesOtherThanIncomeTax
29 Income and social contribution taxes recoverable Concept (Monetary) As Of Debit ifrs-full:CurrentTaxAssetsCurrent
30 Unrealized gains on financial instruments Concept (Monetary) As Of Debit ifrs-full:CurrentDerivativeFinancialAssets
31 Assets held for sale Concept (Monetary) As Of Debit ggb:CurrentAssetsOrDisposalGroupsClassifiedAsHeldForSaleOrAsHeldForDistributionToOwners
32 Other current assets Concept (Monetary) As Of Debit ifrs-full:OtherCurrentFinancialAssets
33 TOTAL CURRENT ASSETS Concept (Monetary) As Of Debit ifrs-full:CurrentAssets
34 NON-CURRENT ASSETS Abstract ifrs-full:NoncurrentAssetsAbstract
35 Tax credits Concept (Monetary) As Of Debit ifrs-full:NoncurrentReceivablesFromTaxesOtherThanIncomeTax
36 Deferred income taxes Concept (Monetary) As Of Debit ifrs-full:DeferredTaxAssets
37 Unrealized gains on financial instruments Concept (Monetary) As Of Debit ifrs-full:NoncurrentDerivativeFinancialAssets
38 Related parties Concept (Monetary) As Of Debit ifrs-full:NoncurrentReceivablesDueFromRelatedParties
39 Judicial deposits Concept (Monetary) As Of Debit ifrs-full:NoncurrentRestrictedCashAndCashEquivalents
40 Other non-current assets Concept (Monetary) As Of Debit ifrs-full:OtherNoncurrentFinancialAssets
41 Prepaid pension cost Concept (Monetary) As Of Debit ifrs-full:AssetsOfBenefitPlan
42 Advance for future investment in joint venture Concept (Monetary) As Of Debit ggb:AdvanceForFutureInvestmentInJointVenture
43 Investments in associates and joint ventures Concept (Monetary) As Of Debit ifrs-full:InvestmentAccountedForUsingEquityMethod
44 Goodwill Concept (Monetary) As Of Debit ifrs-full:Goodwill
45 Other Intangibles Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
46 Property, plant and equipment, net Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
47 TOTAL NON-CURRENT ASSETS Concept (Monetary) As Of Debit ifrs-full:NoncurrentAssets
48 TOTAL ASSETS Concept (Monetary) As Of Debit ifrs-full:Assets
49 EQUITY AND LIABILITIES Abstract ifrs-full:EquityAndLiabilitiesAbstract
50 CURRENT LIABILITIES Abstract ifrs-full:CurrentLiabilitiesAbstract
51 Trade accounts payable Concept (Monetary) As Of Credit ifrs-full:TradeAndOtherCurrentPayablesToTradeSuppliers
52 Short-term debt Concept (Monetary) As Of Credit ggb:CurrentBorrowingsAndCurrentPortionOfNonCurrentBorrowingsExcludingNotesAndDebentures
53 Debentures Concept (Monetary) As Of Credit ifrs-full:CurrentNotesAndDebenturesIssuedAndCurrentPortionOfNoncurrentNotesAndDebenturesIssued
54 Taxes payable Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilitiesCurrent
55 Income and social contribution taxes payable Concept (Monetary) As Of Credit ifrs-full:CurrentPayablesOnSocialSecurityAndTaxesOtherThanIncomeTax
56 Payroll and related liabilities Concept (Monetary) As Of Credit ifrs-full:ShorttermEmployeeBenefitsAccruals
57 Dividends payable Concept (Monetary) As Of Credit ifrs-full:DividendsPayable
58 Employee benefits Concept (Monetary) As Of Credit ifrs-full:CurrentProvisionsForEmployeeBenefits
59 Environmental liabilities Concept (Monetary) As Of Credit ifrs-full:ShorttermProvisionForDecommissioningRestorationAndRehabilitationCosts
60 Unrealized losses on financial instruments Concept (Monetary) As Of Credit ifrs-full:CurrentDerivativeFinancialLiabilities
61 Liabilities held for sale Concept (Monetary) As Of Credit ifrs-full:LiabilitiesIncludedInDisposalGroupsClassifiedAsHeldForSale
62 Other current liabilities Concept (Monetary) As Of Credit ifrs-full:OtherCurrentFinancialLiabilities
63 TOTAL CURRENT LIABILITIES Concept (Monetary) As Of Credit ifrs-full:CurrentLiabilities
64 NON-CURRENT LIABILITIES Abstract ifrs-full:NoncurrentLiabilitiesAbstract
65 Long-term debt Concept (Monetary) As Of Credit ggb:LongTermBorrowingsExcludingNotesAndDebentures
66 Debentures Concept (Monetary) As Of Credit ifrs-full:NoncurrentPortionOfNoncurrentNotesAndDebenturesIssued
67 Related parties Concept (Monetary) As Of Credit ifrs-full:NoncurrentPayablesToRelatedParties
68 Deferred income taxes Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilities
69 Unrealized losses on financial instruments Concept (Monetary) As Of Credit ifrs-full:NoncurrentDerivativeFinancialLiabilities
70 Provision for tax, civil, and labor liabilities Concept (Monetary) As Of Credit ifrs-full:LongtermLegalProceedingsProvision
71 Environmental liabilities Concept (Monetary) As Of Credit ifrs-full:LongtermProvisionForDecommissioningRestorationAndRehabilitationCosts
72 Employee benefits Concept (Monetary) As Of Credit ifrs-full:NoncurrentProvisionsForEmployeeBenefits
73 Obligations with FIDC Concept (Monetary) As Of Credit ggb:NoncurrentObligationsWithSecuritiesAndExchangeCommissionOfBrazil
74 Other non-current liabilities Concept (Monetary) As Of Credit ifrs-full:OtherNoncurrentFinancialLiabilities
75 TOTAL NON-CURRENT LIABILITIES Concept (Monetary) As Of Credit ifrs-full:NoncurrentLiabilities
76 EQUITY Abstract ifrs-full:EquityAbstract
77 Capital Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
78 Treasury stocks Concept (Monetary) As Of Debit ifrs-full:TreasuryShares
79 Capital reserves Concept (Monetary) As Of Credit ifrs-full:CapitalReserve
80 Retained earnings Concept (Monetary) As Of Credit ifrs-full:RetainedEarnings
81 Transactions with non-controlling interests without change of control Concept (Monetary) As Of Debit ggb:OperationsWithNoncontrollingInterests
82 Other reserves Concept (Monetary) As Of Credit ifrs-full:OtherReserves
83 EQUITY ATTRIBUTABLE TO THE EQUITY HOLDERS OF THE PARENT Concept (Monetary) As Of Credit ifrs-full:EquityAttributableToOwnersOfParent
84 NON-CONTROLLING INTERESTS Concept (Monetary) As Of Credit ifrs-full:NoncontrollingInterests
85 EQUITY Concept (Monetary) As Of Credit ifrs-full:Equity
86 TOTAL LIABILITIES AND EQUITY Concept (Monetary) As Of Credit ifrs-full:EquityAndLiabilities
87 00200 - Statement - CONSOLIDATED STATEMENTS OF INCOME/(LOSS) Network

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 http://www.gerdau.com/role/StatementConsolidatedStatementsOfIncomeLoss
88 Implied Table Table

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89 CONSOLIDATED STATEMENTS OF INCOME/(LOSS) Abstract ifrs-full:IncomeStatementAbstract
90 NET SALES Concept (Monetary) For Period Credit ifrs-full:Revenue
91 Cost of sales Concept (Monetary) For Period Debit ifrs-full:CostOfSales
92 GROSS PROFIT Concept (Monetary) For Period Credit ifrs-full:GrossProfit
93 Selling expenses Concept (Monetary) For Period Debit ifrs-full:SellingExpense
94 Impairment loss on trade receivables Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossRecognisedInProfitOrLossTradeReceivables
95 General and administrative expenses Concept (Monetary) For Period Debit ifrs-full:GeneralAndAdministrativeExpense
96 Other operating income Concept (Monetary) For Period Credit ifrs-full:OtherIncome
97 Other operating expenses Concept (Monetary) For Period Debit ifrs-full:OtherExpenseByFunction
98 Impairment of non-financial assets Concept (Monetary) For Period Debit ggb:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipmentAndGoodwill
99 Gains and losses on assets held for sale and sales of interest in subsidiaries Concept (Monetary) For Period Credit ggb:GainsLossesOnAssetsHeldForSaleAndSalesOfInterestInSubsidiariesAndAssociates
100 Reversal of provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalNet
101 Equity method investees Concept (Monetary) For Period Credit ggb:ShareOfProfitLossOfInvestmentsAccountedForUsingEquityMethod
102 INCOME (LOSS) BEFORE FINANCIAL INCOME (EXPENSES) AND TAXES Concept (Monetary) For Period Credit ifrs-full:ProfitLossFromOperatingActivities
103 Financial income Concept (Monetary) For Period Credit ifrs-full:FinanceIncome
104 Financial expenses Concept (Monetary) For Period Debit ifrs-full:FinanceCosts
105 Bonds Repurchases expenses Concept (Monetary) For Period Debit ggb:RepurchaseOfBonds
106 Exchange variations, net Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
107 Reversal of interest on provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:FinancialIncomeFromReversalOfContingentTaxLiabilities
108 Gains and losses on derivative financial instruments, net Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnChangeInFairValueOfDerivatives
109 INCOME (LOSS) BEFORE TAXES Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
110 Income and social contribution taxes Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
111 Current Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncome
112 Deferred Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncome
113 Income and social contribution taxes Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
114 NET INCOME (LOSS) Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
115 ATTRIBUTABLE TO: Abstract ifrs-full:ProfitLossAttributableToAbstract
116 Owners of the parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
117 Non-controlling interests Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToNoncontrollingInterests
118 NET INCOME (LOSS) Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
119 EARNINGS PER SHARE Abstract ifrs-full:EarningsPerShareAbstract
120 Basic earnings/(loss) per share - preferred and common - (R$) Concept (Share) For Period ifrs-full:BasicEarningsLossPerShare
121 Diluted earnings/(loss) per share - preferred and common - (R$) Concept (Share) For Period ifrs-full:DilutedEarningsLossPerShare
122 00300 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) Network

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 http://www.gerdau.com/role/StatementConsolidatedStatementsOfComprehensiveIncomeLoss
123 Implied Table Table

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124 CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) Abstract ifrs-full:StatementOfComprehensiveIncomeAbstract
125 Net income (loss) for the year Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
126 Items that may be reclassified subsequently to profit or loss Abstract ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTaxAbstract
127 Other comprehensive income from associates and joint ventures Concept (Monetary) For Period Credit ifrs-full:ShareOfOtherComprehensiveIncomeOfAssociatesAndJointVenturesAccountedForUsingEquityMethodThatWillBeReclassifiedToProfitOrLossNetOfTax
128 Cumulative translation adjustment Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationNetOfTax
129 Recycling of cumulative translation adjustment to net income Concept (Monetary) For Period Debit ifrs-full:ReclassificationAdjustmentsOnExchangeDifferencesOnTranslationNetOfTax
130 Unrealized (Losses) Gains on net investment hedge Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnHedgesOfNetInvestmentsInForeignOperationsNetOfTax
131 Cash flow hedges Abstract ifrs-full:CashFlowHedgesAbstract
132 Unrealized Gains (Losses) on Financial Instruments, net of tax Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnCashFlowHedgesNetOfTax
133 Total items that may be reclassified subsequently to profit or loss Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTax
134 Items that will not be reclassified subsequently to profit or loss Abstract ifrs-full:ComponentsOfOtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTaxAbstract
135 Remeasurement of defined benefit pension plan, net of tax Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeNetOfTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
136 Total items that will not be reclassified subsequently to profit or loss Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTax
137 Other comprehensive income (loss), net of tax Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncome
138 Total comprehensive income (loss) for the year, net of tax Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
139 Total comprehensive income/(loss) attributable to: Abstract ifrs-full:ComprehensiveIncomeAttributableToAbstract
140 Owners of the parent Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToOwnersOfParent
141 Non-controlling interests Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncomeAttributableToNoncontrollingInterests
142 Total comprehensive income (loss) for the year, net of tax Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
143 00400 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY Network

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 http://www.gerdau.com/role/StatementConsolidatedStatementsOfChangesInEquity
144 Statement of changes in equity [table] Table

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 ifrs-full:StatementOfChangesInEquityTable
145 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
146 Equity [member] Member ifrs-full:EquityMember
147 Total Parent company's interest Member ifrs-full:EquityAttributableToOwnersOfParentMember
148 Capital Member ifrs-full:IssuedCapitalMember
149 Treasury Stocks Member ifrs-full:TreasurySharesMember
150 Capital Reserve Member ifrs-full:CapitalReserveMember
151 Legal reserve Member ifrs-full:StatutoryReserveMember
152 Tax Incentives Reserve Member ggb:TaxIncentivesReserveMember
153 Investments and working capital reserve Member ggb:InvestmentsAndWorkingCapitalReserveMember
154 Retained earnings Member ifrs-full:RetainedEarningsMember
155 Operations with noncontrolling interests Member ggb:OperationsWithNoncontrollingInterestsMember
156 Gains and losses on net investment hedge Member ifrs-full:ReserveOfGainsAndLossesOnHedgingInstrumentsThatHedgeInvestmentsInEquityInstrumentsMember
157 Gains and losses on financial instruments Member ifrs-full:ReserveOfCashFlowHedgesMember
158 Cumulative translation adjustment Member ifrs-full:ReserveOfExchangeDifferencesOnTranslationMember
159 Pension Plan Member ifrs-full:ReserveOfRemeasurementsOfDefinedBenefitPlansMember
160 Stock Options Member ifrs-full:ReserveOfChangeInValueOfTimeValueOfOptionsMember
161 Non-controlling interests Member ifrs-full:NoncontrollingInterestsMember
162 Initially applied IFRSs [axis] Axis ifrs-full:InitiallyAppliedIFRSsAxis
163 Initially applied IFRSs [member] Member ifrs-full:InitiallyAppliedIFRSsMember
164 Initial application of IFRS 9 Member ifrs-full:InAccordanceWithIFRS9Member
165 CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY LineItems ifrs-full:StatementOfChangesInEquityLineItems
166 Equity at beginning of period Concept (Monetary) As Of Credit ifrs-full:Equity
167 Net income (loss) Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
168 Other comprehensive income (loss) recognized in the year Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncome
169 Total comprehensive income (loss) for the year, net of tax Concept (Monetary) For Period Credit ifrs-full:ComprehensiveIncome
170 Stock option expenses recognized in the year Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughSharebasedPaymentTransactions
171 Treasury stocks Concept (Monetary) For Period Debit ifrs-full:PurchaseOfTreasuryShares
172 Effects of IAS 29 adoption in the subsidiary of Argentina Concept (Monetary) For Period Credit ggb:EffectsOfApplicationOfIas29RecognizedInEquityNetOfTax
173 Assignment of preferred shares Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTreasuryShareTransactions
174 Stock option exercised during the year Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughExerciseOfOptions
175 Effect of interest changes in subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangeInEquityOfSubsidiaries
176 Complementary Dividends Concept (Monetary) For Period Debit ggb:ComplementaryDividends
177 Legal reserve Concept (Monetary) For Period Credit ggb:LegalReserve
178 Tax incentives reserve Concept (Monetary) For Period Credit ggb:TaxIncentivesReserve
179 Investments and working capital reserve Concept (Monetary) For Period Debit ggb:DecreaseInEquityThroughAppropriationOfRetainedEarningsToReserves
180 Absorption of net loss proposed to the shareholders Concept (Monetary) For Period Credit ggb:IncreaseInEquityThroughTransferOfReservesToRetainedEarnings
181 Dividends/interest on capital Concept (Monetary) For Period Debit ggb:InterestAndDividendsPaidFromInvestmentsAndWorkingCapitalReserve
182 Dividends/interest on capital Concept (Monetary) For Period Debit ggb:InterestAndDividendsPaidFromRetainedEarnings
183 Effects of IFRS 9 adoption, net of taxes Concept (Monetary) As Of Credit ggb:IfrsCumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
184 Equity at end of period Concept (Monetary) As Of Credit ifrs-full:Equity
185 00500 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS Network

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 http://www.gerdau.com/role/StatementConsolidatedStatementsOfCashFlows
186 Implied Table Table

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187 CONSOLIDATED STATEMENTS OF CASH FLOWS Abstract ifrs-full:StatementOfCashFlowsAbstract
188 Cash flows from operating activities Abstract ifrs-full:CashFlowsFromUsedInOperatingActivitiesAbstract
189 Net income (loss) for the year Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
190 Adjustments to reconcile net income for the year to net cash provided by operating activities Abstract ifrs-full:AdjustmentsForReconcileProfitLossAbstract
191 Depreciation and amortization Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDepreciationAndAmortisationExpense
192 Impairment of Assets Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLoss
193 Equity method investees Concept (Monetary) For Period Credit ifrs-full:AdjustmentsForUndistributedProfitsOfInvestmentsAccountedForUsingEquityMethod
194 Exchange variation, net Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForUnrealisedForeignExchangeLossesGains
195 (Gains) Losses on financial instruments, net Concept (Monetary) For Period Credit ifrs-full:AdjustmentsForGainsLossesOnChangeInFairValueOfDerivatives
196 Post-employment benefits Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInEmployeeBenefitLiabilities
197 Stock based compensation Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForSharebasedPayments
198 Income tax Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncomeTaxExpense
199 Gains on disposal of property, plant and equipment Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForLossesGainsOnDisposalOfNoncurrentAssets
200 Results in operations with subsidiaries Concept (Monetary) For Period Credit ggb:GainsLossesOnAssetsHeldForSaleAndSalesOfInterestInSubsidiariesAndAssociates
201 Impairment loss on trade receivables Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInTradeAndOtherReceivables
202 Provision for tax, labor and civil claims Concept (Monetary) For Period Debit ggb:AdjustmentsForProvisionForLegalProceedingsClaims
203 Reversal of contingent liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalNet
204 Interest income on short-term investments Concept (Monetary) For Period Credit ifrs-full:AdjustmentsForInterestIncome
205 Interest expense on loans Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForInterestExpense
206 Reversal of monetary update of contingent liabilities, net Concept (Monetary) For Period Credit ggb:FinancialIncomeFromReversalOfContingentTaxLiabilities
207 Interest on loans with related parties Concept (Monetary) For Period Debit ggb:AdjustmentsForInterestExpenseOnLoansWithRelatedParties
208 Provision (Reversal) for net realisable value adjustment in inventory Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLossInventories
209 Cash flows from operations before changes in working capital Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperationsBeforeChangesInWorkingCapital
210 Changes in assets and liabilities Abstract ggb:ChangesInAssetsAndLiabilitiesAbstract
211 Decrease (Increase) in trade accounts receivable Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInTradeAccountReceivable
212 (Increase) Decrease in inventories Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInInventories
213 Increase in trade accounts payable Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInTradeAccountPayable
214 Increase in other receivables Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForDecreaseIncreaseInOtherOperatingReceivables
215 Decrease in other payables Concept (Monetary) For Period Debit ifrs-full:AdjustmentsForIncreaseDecreaseInOtherOperatingPayables
216 Dividends from joint ventures Concept (Monetary) For Period Debit ifrs-full:DividendsReceivedClassifiedAsOperatingActivities
217 Purchases of trading securities Concept (Monetary) For Period Credit ggb:PurchaseOfTradingFinancialAssets
218 Proceeds from maturities and sales of trading securities Concept (Monetary) For Period Debit ggb:ProceedsFromSaleOrMaturityOfTradingFinancialAssets
219 Cash provided by operating activities Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperations
220 Interest paid on loans and financing Concept (Monetary) For Period Credit ifrs-full:InterestPaidClassifiedAsOperatingActivities
221 Income and social contributions taxes paid Concept (Monetary) For Period Credit ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities
222 Net cash provided by operating activities Concept (Monetary) For Period ifrs-full:CashFlowsFromUsedInOperatingActivities
223 Cash flows from investing activities Abstract ifrs-full:CashFlowsFromUsedInInvestingActivitiesAbstract
224 Purchases of property, plant and equipment Concept (Monetary) For Period Credit ifrs-full:PurchaseOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities
225 Proceeds from sales of property, plant and equipment, investments and other intangibles Concept (Monetary) For Period Debit ifrs-full:ProceedsFromDisposalsOfPropertyPlantAndEquipmentIntangibleAssetsOtherThanGoodwillInvestmentPropertyAndOtherNoncurrentAssets
226 Purchases of other intangibles Concept (Monetary) For Period Credit ifrs-full:PurchaseOfIntangibleAssetsClassifiedAsInvestingActivities
227 Advance for future investment in joint venture Concept (Monetary) For Period Credit ifrs-full:CashAdvancesAndLoansMadeToOtherPartiesClassifiedAsInvestingActivities
228 Capital increase in joint venture Concept (Monetary) For Period Credit ifrs-full:PurchaseOfInterestsInInvestmentsAccountedForUsingEquityMethod
229 Net cash provided (used) in investing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInInvestingActivities
230 Cash flows from financing activities Abstract ifrs-full:CashFlowsFromUsedInFinancingActivitiesAbstract
231 Purchase of treasury shares Concept (Monetary) For Period Credit ifrs-full:PaymentsToAcquireOrRedeemEntitysShares
232 Dividends and interest on capital paid Concept (Monetary) For Period Credit ifrs-full:DividendsPaidClassifiedAsFinancingActivities
233 Proceeds from loans and financing Concept (Monetary) For Period Debit ifrs-full:ProceedsFromBorrowingsClassifiedAsFinancingActivities
234 Repayment of loans and financing Concept (Monetary) For Period Credit ifrs-full:RepaymentsOfBorrowingsClassifiedAsFinancingActivities
235 Intercompany loans, net Concept (Monetary) For Period Debit ggb:ProceedsFromPaymentsToIntercompanyLoansNet
236 Net cash used in financing activities Concept (Monetary) For Period Debit ifrs-full:CashFlowsFromUsedInFinancingActivities
237 Exchange variation on cash and cash equivalents Concept (Monetary) For Period Debit ifrs-full:EffectOfExchangeRateChangesOnCashAndCashEquivalents
238 Increase (Decrease) in cash and cash equivalents Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseInCashAndCashEquivalents
239 Cash and cash equivalents at beginning of year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
240 Cash and cash equivalents at end of year Concept (Monetary) As Of Debit ifrs-full:CashAndCashEquivalents
241 10101 - Disclosure - GENERAL INFORMATION Network

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242 Implied Table Table

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243 GENERAL INFORMATION Abstract ggb:DisclosureOfGeneralInformationAboutFinancialStatementsAbstract
244 GENERAL INFORMATION Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGeneralInformationAboutFinancialStatementsExplanatory
245 10201 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES Network

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 http://www.gerdau.com/role/DisclosureSummaryOfSignificantAccountingPractices
246 Implied Table Table

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247 SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES Abstract ggb:IfrsAccountingPoliciesAbstract
248 SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSummaryOfSignificantAccountingPoliciesExplanatory
249 10301 - Disclosure - CONSOLIDATED FINANCIAL STATEMENTS Network

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250 Implied Table Table

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251 CONSOLIDATED FINANCIAL STATEMENTS Abstract ggb:DisclosureOfInformationAboutConsolidatedFinancialStatementsAbstract
252 CONSOLIDATED FINANCIAL STATEMENTS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestsInOtherEntitiesExplanatory
253 10401 - Disclosure - CASH AND CASH EQUIVALENTS, AND SHORT AND LONG-TERM INVESTMENTS Network

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 http://www.gerdau.com/role/DisclosureCashAndCashEquivalentsAndShortAndLongTermInvestments
254 Implied Table Table

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255 CASH AND CASH EQUIVALENTS, AND SHORT AND LONG-TERM INVESTMENTS Abstract ggb:CashCashEquivalentsAndShortAndLongTermInvestmentsAbstract
256 CASH AND CASH EQUIVALENTS, AND SHORT AND LONG-TERM INVESTMENTS Concept (Text Block (HTML)) For Period ggb:DisclosureOfCashCashEquivalentsAndShortAndLongTermInvestmentsTextBlock
257 10501 - Disclosure - TRADE ACCOUNTS RECEIVABLE Network

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258 Implied Table Table

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259 TRADE ACCOUNTS RECEIVABLE Abstract ifrs-full:TradeAndOtherCurrentReceivablesAbstract
260 TRADE ACCOUNTS RECEIVABLE Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTradeAndOtherReceivablesExplanatory
261 10601 - Disclosure - INVENTORIES Network

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262 Implied Table Table

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263 INVENTORIES Abstract ifrs-full:ClassesOfInventoriesAbstract
264 INVENTORIES Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInventoriesExplanatory
265 10701 - Disclosure - TAX CREDITS Network

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266 Implied Table Table

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267 TAX CREDITS Abstract ggb:TaxCreditsAbstract
268 TAX CREDITS Concept (Text Block (HTML)) For Period ggb:DisclosureOfTaxCreditsTextBlock
269 10801 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES Network

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270 Implied Table Table

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271 INCOME AND SOCIAL CONTRIBUTION TAXES Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
272 INCOME AND SOCIAL CONTRIBUTION TAXES Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIncomeTaxExplanatory
273 10901 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES Network

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274 Implied Table Table

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275 INVESTMENTS IN ASSOCIATES AND JOINT VENTURES Abstract ifrs-full:InvestmentsInSubsidiariesJointVenturesAndAssociatesAbstract
276 INVESTMENTS IN ASSOCIATES AND JOINT VENTURES Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInvestmentsAccountedForUsingEquityMethodExplanatory
277 11001 - Disclosure - PROPERTY, PLANT AND EQUIPMENT Network

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278 Implied Table Table

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279 PROPERTY, PLANT AND EQUIPMENT Abstract ifrs-full:DisclosureOfPropertyPlantAndEquipmentAbstract
280 PROPERTY, PLANT AND EQUIPMENT Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfPropertyPlantAndEquipmentExplanatory
281 11101 - Disclosure - GOODWILL Network

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282 Implied Table Table

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283 GOODWILL Abstract ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillAbstract
284 GOODWILL Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGoodwillExplanatory
285 11201 - Disclosure - INTANGIBLE ASSETS Network

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286 Implied Table Table

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287 INTANGIBLE ASSETS Abstract ifrs-full:DisclosureOfIntangibleAssetsAbstract
288 INTANGIBLE ASSETS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfIntangibleAssetsExplanatory
289 11301 - Disclosure - LOANS AND FINANCING Network

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290 Implied Table Table

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291 LOANS AND FINANCING Abstract ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsAbstract
292 LOANS AND FINANCING Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfBorrowingsExplanatory
293 11401 - Disclosure - DEBENTURES Network

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294 Implied Table Table

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295 DEBENTURES Abstract ggb:DisclosureOfDebenturesAbstract
296 DEBENTURES Concept (Text Block (HTML)) For Period ggb:DisclosureOfDebenturesTextBlock
297 11501 - Disclosure - FINANCIAL INSTRUMENTS Network

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298 Implied Table Table

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299 FINANCIAL INSTRUMENTS Abstract ifrs-full:DisclosureOfFinancialInstrumentsAbstract
300 FINANCIAL INSTRUMENTS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialInstrumentsExplanatory
301 11601 - Disclosure - TAXES PAYABLE Network

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302 Implied Table Table

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303 TAXES PAYABLE Abstract ggb:TaxesPayableAbstract
304 TAXES PAYABLE Concept (Text Block (HTML)) For Period ggb:DisclosureOfTaxesPayableTextBlock
305 11701 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS Network

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306 Implied Table Table

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307 TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS Abstract ggb:DisclosureOfTaxCivilAndLaborClaimsAndContingentAssetsAbstract
308 TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOtherProvisionsContingentLiabilitiesAndContingentAssetsExplanatory
309 11801 - Disclosure - RELATED-PARTY TRANSACTIONS Network

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310 Implied Table Table

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311 RELATED-PARTY TRANSACTIONS Abstract ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesAbstract
312 RELATED-PARTY TRANSACTIONS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRelatedPartyExplanatory
313 11901 - Disclosure - EMPLOYEE BENEFITS Network

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314 Implied Table Table

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315 EMPLOYEE BENEFITS Abstract ifrs-full:DisclosureOfDefinedBenefitPlansAbstract
316 EMPLOYEE BENEFITS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEmployeeBenefitsExplanatory
317 12001 - Disclosure - ENVIRONMENTAL LIABILITIES Network

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318 Implied Table Table

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319 ENVIRONMENTAL LIABILITIES Abstract ggb:DisclosureOfEnvironmentalLiabilitiesAbstract
320 ENVIRONMENTAL LIABILITIES Concept (Text Block (HTML)) For Period ggb:DisclosureOfEnvironmentalLiabilitiesTextBlock
321 12101 - Disclosure - OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS Network

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322 Implied Table Table

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323 OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS Abstract ggb:ObligationsWithSecuritiesAndExchangeCommissionOfBrazilAndInvestmentFundInCreditRightsAbstract
324 OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS Concept (Text Block (HTML)) For Period ggb:ObligationsWithSecuritiesAndExchangeCommissionOfBrazilAndInvestmentFundInCreditRightsTextBlock
325 12201 - Disclosure - EQUITY Network

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326 Implied Table Table

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327 EQUITY Abstract ifrs-full:DisclosureOfClassesOfShareCapitalAbstract
328 EQUITY Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfShareCapitalReservesAndOtherEquityInterestExplanatory
329 12301 - Disclosure - EARNINGS (LOSS) PER SHARE (EPS) Network

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330 Implied Table Table

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331 EARNINGS (LOSS) PER SHARE (EPS) Abstract ifrs-full:EarningsPerShareAbstract
332 EARNINGS (LOSS) PER SHARE (EPS) Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEarningsPerShareExplanatory
333 12401 - Disclosure - NET SALES Network

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334 Implied Table Table

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335 NET SALES Abstract ifrs-full:RevenueAbstract
336 NET SALES Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRevenueExplanatory
337 12501 - Disclosure - LONG-TERM INCENTIVE PLANS Network

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338 Implied Table Table

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339 LONG-TERM INCENTIVE PLANS Abstract ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementAbstract
340 LONG-TERM INCENTIVE PLANS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSharebasedPaymentArrangementsExplanatory
341 12601 - Disclosure - SEGMENT REPORTING Network

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342 Implied Table Table

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343 SEGMENT REPORTING Abstract ifrs-full:DisclosureOfOperatingSegmentsAbstract
344 SEGMENT REPORTING Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfEntitysReportableSegmentsExplanatory
345 12701 - Disclosure - INSURANCE Network

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346 Implied Table Table

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347 INSURANCE Abstract ifrs-full:DisclosureOfTypesOfInsuranceContractsAbstract
348 INSURANCE Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInsuranceContractsExplanatory
349 12801 - Disclosure - IMPAIRMENT OF ASSETS Network

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350 Implied Table Table

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351 IMPAIRMENT OF ASSETS Abstract ifrs-full:DisclosureOfImpairmentLossAndReversalOfImpairmentLossAbstract
352 IMPAIRMENT OF ASSETS Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfImpairmentOfAssetsExplanatory
353 12901 - Disclosure - EXPENSES BY NATURE Network

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354 Implied Table Table

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355 EXPENSES BY NATURE Abstract ifrs-full:ExpenseByNatureAbstract
356 EXPENSES BY NATURE Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfExpensesByNatureExplanatory
357 13001 - Disclosure - FINANCIAL INCOME Network

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358 Implied Table Table

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359 FINANCIAL INCOME Abstract ggb:FinancialIncomeAbstract
360 FINANCIAL INCOME Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinanceIncomeExplanatory
361 20202 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES (Policies) Network

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362 Implied Table Table

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363 SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES Abstract ggb:IfrsAccountingPoliciesAbstract
364 Basis of Presentation Concept (Text Block (HTML)) For Period ifrs-full:ExplanationOfMeasurementBasesUsedInPreparingFinancialStatements
365 Foreign Currency Translation Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForForeignCurrencyTranslationExplanatory
366 Financial Assets Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForFinancialAssetsExplanatory
367 Inventories Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForMeasuringInventories
368 Property, Plant and Equipment Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForPropertyPlantAndEquipmentExplanatory
369 Goodwill Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForGoodwillExplanatory
370 Other Intangible Assets Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIntangibleAssetsOtherThanGoodwillExplanatory
371 Provision for Impairment of Assets and Reversal of Impairment Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForProvisionsExplanatory
372 Financial Liabilities and Equity Instruments Concept (Text Block (HTML)) For Period ggb:DescriptionOfAccountingPolicyForFinancialLiabilitiesAndEquityInstrumentsPolicyTextBlock
373 Current and Deferred Income and Social Contribution Taxes Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForIncomeTaxExplanatory
374 Employee Benefits Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForEmployeeBenefitsExplanatory
375 Other Current and Non-current Assets and Liabilities Concept (Text Block (HTML)) For Period ggb:DescriptionOfAccountingPolicyForOtherCurrentAndNoncurrentAssetsAndLiabilitiesPolicyTextBlock
376 Related -Party Transactions Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForTransactionsWithRelatedPartiesExplanatory
377 Dividends and Interest on equity Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForDividendsExplanatory
378 Revenue Recognition Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForRecognitionOfRevenue
379 Investments in Environmental Protection and Environmental liabilities Concept (Text Block (HTML)) For Period ggb:DescriptionOfAccountingPolicyForInvestmentsInEnvironmentalProtectionsAndEnvironmentalLiabilitiesPolicyTextBlock
380 Use of Judgements and Estimates Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfAccountingJudgementsAndEstimatesExplanatory
381 Business Combinations for the Financial Statements Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForBusinessCombinationsExplanatory
382 Segment Information Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForSegmentReportingExplanatory
383 Earnings per Share Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForEarningsPerShareExplanatory
384 Long-term incentive plans Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForSharebasedPaymentTransactionsExplanatory
385 Assets and liabilities held for sale Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfAccountingPolicyForNoncurrentAssetsOrDisposalGroupsClassifiedAsHeldForSaleExplanatory
386 New IFRS and Interpretations of IFRIC Concept (Text Block (HTML)) For Period ggb:DescriptionOfAccountingPolicyForNewAccountingPronouncementsPolicyTextBlock
387 30203 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES (Tables) Network

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388 Implied Table Table

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389 SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES Abstract ggb:IfrsAccountingPoliciesAbstract
390 Summary of initial application of IFRS 9 as it relates to measurement categories of financial assets and liabilities Concept (Text Block (HTML)) For Period ifrs-full:DescriptionOfInitialApplicationOfStandardsOrInterpretations
391 30303 - Disclosure - CONSOLIDATED FINANCIAL STATEMENTS (Tables) Network

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392 Implied Table Table

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393 CONSOLIDATED FINANCIAL STATEMENTS Abstract ggb:DisclosureOfInformationAboutConsolidatedFinancialStatementsAbstract
394 Schedule of significant consolidated subsidiaries Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSignificantInvestmentsInSubsidiariesExplanatory
395 Schedule of interests in joint ventures Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfJointOperationsExplanatory
396 Schedule of summarized financial information of the joint ventures Concept (Text Block (HTML)) For Period ggb:DisclosureOfSignificantInvestmentsInJointlyControlledEntitiesTableTextBlock
397 Schedule of interests in associate companies Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInterestsInAssociatesExplanatory
398 Schedule of summarized financial information of the associate companies Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSignificantInvestmentsInAssociatesExplanatory
399 30403 - Disclosure - CASH AND CASH EQUIVALENTS, AND SHORT AND LONG-TERM INVESTMENTS (Tables) Network

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400 Implied Table Table

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401 CASH AND CASH EQUIVALENTS, AND SHORT AND LONG-TERM INVESTMENTS Abstract ggb:CashCashEquivalentsAndShortAndLongTermInvestmentsAbstract
402 Schedule of cash and cash equivalents and investments Concept (Text Block (HTML)) For Period ggb:DisclosureOfCashCashEquivalentsAndShortAndLongTermInvestmentsTableTextBlock
403 30503 - Disclosure - TRADE ACCOUNTS RECEIVABLE (Tables) Network

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404 Implied Table Table

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405 TRADE ACCOUNTS RECEIVABLE Abstract ifrs-full:TradeAndOtherCurrentReceivablesAbstract
406 Schedule of trade accounts receivable Concept (Text Block (HTML)) For Period ggb:DisclosureOfTradeAccountsReceivablesTableTextBlock
407 Schedule of accounts receivable by aging Concept (Text Block (HTML)) For Period ggb:DisclosureOfAccountsReceivableByAgingTableTextBlock
408 Schedule of the changes in the allowance for doubtful accounts Concept (Text Block (HTML)) For Period ggb:DisclosureOfChangesInAllowanceForDoubtfulAccountsTableTextBlock
409 30603 - Disclosure - INVENTORIES (Tables) Network

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410 Implied Table Table

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411 INVENTORIES Abstract ifrs-full:ClassesOfInventoriesAbstract
412 Schedule of inventories Concept (Text Block (HTML)) For Period ggb:DisclosureOfCurrentInventoriesTableTextBlock
413 Schedule of the changes in the allowance for adjustment to net realizable value of inventories Concept (Text Block (HTML)) For Period ggb:DisclosureOfChangesInAllowanceForInventoriesAdjustmentToNetRealizableValueTableTextBlock
414 30703 - Disclosure - TAX CREDITS (Tables) Network

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415 Implied Table Table

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416 TAX CREDITS Abstract ggb:TaxCreditsAbstract
417 Schedule of current and non-current tax credits Concept (Text Block (HTML)) For Period ggb:DisclosureOfCurrentAndNonCurrentTaxCreditsTableTextBlock
418 Schedule of estimates of realization of non-current tax credits Concept (Text Block (HTML)) For Period ggb:DisclosureOfEstimatesOfRealizationOfNonCurrentTaxCreditsTableTextBlock
419 30803 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES (Tables) Network

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420 Implied Table Table

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421 INCOME AND SOCIAL CONTRIBUTION TAXES Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
422 Schedule of reconciliations of income and social contribution taxes at statutory rates to amounts presented in the Statement Of Income Concept (Text Block (HTML)) For Period ggb:ScheduleOfTaxRateReconciliationTableTextBlock
423 Schedule of breakdown and changes in deferred income and social contribution tax assets and liabilities at statutory tax rates Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsExplanatory
424 Schedule of estimated recovery and reversal of income and social contributions tax assets and liabilities Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDeferredTaxesExplanatory
425 30903 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES (Tables) Network

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426 Implied Table Table

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427 INVESTMENTS IN ASSOCIATES AND JOINT VENTURES Abstract ifrs-full:InvestmentsInSubsidiariesJointVenturesAndAssociatesAbstract
428 Summary of investments in associates and joint ventures Concept (Text Block (HTML)) For Period ggb:DisclosureOfInvestmentsAccountedForUsingEquityMethodTableTextBlock
429 31003 - Disclosure - PROPERTY, PLANT AND EQUIPMENT (Tables) Network

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430 Implied Table Table

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431 PROPERTY, PLANT AND EQUIPMENT Abstract ifrs-full:DisclosureOfPropertyPlantAndEquipmentAbstract
432 Summary of changes in property, plant and equipment Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutPropertyPlantAndEquipmentExplanatory
433 Summary of useful lives of property, plant and equipment Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDepreciationAndAmortisationExpenseExplanatory
434 31103 - Disclosure - GOODWILL (Tables) Network

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435 Implied Table Table

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436 GOODWILL Abstract ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillAbstract
437 Summary of changes in goodwill Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillExplanatory
438 Schedule of goodwill by segment Concept (Text Block (HTML)) For Period ggb:DisclosureOfGoodwillBySegmentTextBlock
439 31203 - Disclosure - INTANGIBLE ASSETS (Tables) Network

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440 Implied Table Table

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441 INTANGIBLE ASSETS Abstract ifrs-full:DisclosureOfIntangibleAssetsAbstract
442 Summary of intangible assets Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutIntangibleAssetsExplanatory
443 Summary of intangible assets by segment Concept (Text Block (HTML)) For Period ggb:DisclosureOfIntangibleAssetsBySegmentTextBlock
444 31303 - Disclosure - LOANS AND FINANCING (Tables) Network

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445 Implied Table Table

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446 LOANS AND FINANCING Abstract ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsAbstract
447 Schedule of loans and financing Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsExplanatory
448 Schedule of loans and financing by currency Concept (Text Block (HTML)) For Period ggb:ScheduleOfLoansAndFinancingByCurrencyTableTextBlock
449 Schedule of amortization of long term loans and financing Concept (Text Block (HTML)) For Period ifrs-full:MaturityAnalysisForNonderivativeFinancialLiabilities
450 31403 - Disclosure - DEBENTURES (Tables) Network

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451 Implied Table Table

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452 DEBENTURES Abstract ggb:DisclosureOfDebenturesAbstract
453 Schedule of debentures Concept (Text Block (HTML)) For Period ggb:DisclosureOfDetailedInformationAboutDebenturesTableTextBlock
454 Schedule of amortization of long term debentures Concept (Text Block (HTML)) For Period ggb:DisclosureOfDetailedInformationAboutAmortizationSchedulesOfDebenturesTableTextBlock
455 31503 - Disclosure - FINANCIAL INSTRUMENTS (Tables) Network

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456 Implied Table Table

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457 FINANCIAL INSTRUMENTS Abstract ifrs-full:DisclosureOfFinancialInstrumentsAbstract
458 Summary of fair value of financial instruments Concept (Text Block (HTML)) For Period ggb:DisclosureOfMarketValueOfFinancialInstrumentsTableTextBlock
459 Schedule of capital management risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFinancialRiskManagementExplanatory
460 Schedule of maturity of contractual obligations for liquidity risk Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfLiquidityRiskExplanatory
461 Schedule of sensitivity analysis Concept (Text Block (HTML)) For Period ifrs-full:SensitivityAnalysisForEachTypeOfMarketRisk
462 Schedule of financial instruments per category Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDetailedInformationAboutFinancialInstrumentsExplanatory
463 Summary of derivative instruments Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfDerivativeFinancialInstrumentsExplanatory
464 Summary of prospective and retrospective tests of derivative financial instruments Concept (Text Block (HTML)) For Period ggb:SummaryOfEffectivenessTestingForDerivativeFinancialInstrumentsTableTextBlock
465 Schedule of financial assets and liabilities measures at fair value on recurring basis Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfFairValueOfFinancialInstrumentsExplanatory
466 Summary of changes in liabilities of cash flow from financing activities Concept (Text Block (HTML)) For Period ggb:SummaryOfChangesInLiabilitiesOfCashFlowFromFinancingActivitiesTableTextBlock
467 31603 - Disclosure - TAXES PAYABLE (Tables) Network

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468 Implied Table Table

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469 TAXES PAYABLE Abstract ggb:TaxesPayableAbstract
470 Schedule of taxes payable Concept (Text Block (HTML)) For Period ggb:DisclosureOfTaxesPayableTableTextBlock
471 31703 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS (Tables) Network

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472 Implied Table Table

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474 Schedule of provisions for tax, civil and labor claims Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfOtherProvisionsExplanatory
475 Schedule of changes in the tax, labor and civil provisions Concept (Text Block (HTML)) For Period ggb:ScheduleOfChangesInTaxLaborAndCivilProvisionsTableTextBlock
476 Schedule of judicial deposits related to tax, labor and civil lawsuits Concept (Text Block (HTML)) For Period ggb:ScheduleOfNoncurrentRestrictedCashAndCashEquivalentsRelatedToTaxLaborAndCivilMattersTableTextBlock
477 31803 - Disclosure - RELATED-PARTY TRANSACTIONS (Tables) Network

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478 Implied Table Table

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479 RELATED-PARTY TRANSACTIONS Abstract ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesAbstract
480 Schedule of intercompany loans Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesExplanatory
481 Summary of guarantees granted Concept (Text Block (HTML)) For Period ggb:DisclosureOfInformationAboutGuaranteesGrantedTableTextBlock
482 Schedule of key management compensation Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfInformationAboutKeyManagementPersonnelExplanatory
483 31903 - Disclosure - EMPLOYEE BENEFITS (Tables) Network

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484 Disclosure of net defined benefit liability (asset) [table] Table

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487 Post-employment defined benefit pension plans Member ggb:PostEmploymentDefinedBenefitPensionPlanMember
488 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
489 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
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491 Schedule of total assets and liabilities of all types of employee benefits granted Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetExplanatory
492 Summary of sensitivity analysis Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsExplanatory
493 Schedule of current expenses of benefit plans Concept (Text Block (HTML)) For Period ggb:DisclosureOfCurrentExpensesOfDefinedBenefitPlansExplanatoryTableTextBlock
494 Schedule of reconciliations of assets and liabilities of benefit plans Concept (Text Block (HTML)) For Period ggb:DisclosureOfReconciliationsOfAssetsAndLiabilitiesOfBenefitPlansTableTextBlock
495 Schedule of variation of plan obligations and assets Concept (Text Block (HTML)) For Period ggb:DisclosureOfChangesInPlanAssetsAndPlanObligationsExplanatoryTableTextBlock
496 Summary of actuarial gains and losses recognized in other comprehensive income Concept (Text Block (HTML)) For Period ggb:DisclosureOfAmountsRecognizedAsActuarialGainsAndLossesInStatementOfComprehensiveIncomeExplanatoryTableTextBlock
497 Summary of historical actuarial remeasurements Concept (Text Block (HTML)) For Period ggb:DisclosureOfHistoricalActuarialRemeasurementsOfDefinedBenefitPlansExplanatoryTableTextBlock
498 Summary of allocation for plan assets Concept (Text Block (HTML)) For Period ggb:DisclosureOfAllocationOfDefinedBenefitPlanAssetsExplanatoryTableTextBlock
499 Summary of assumptions Concept (Text Block (HTML)) For Period ggb:DisclosureOfAssumptionsUsedToCalculateDefinedBenefitPlansExplanatoryTableTextBlock
500 32003 - Disclosure - ENVIRONMENTAL LIABILITIES (Tables) Network

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504 32203 - Disclosure - EQUITY (Tables) Network

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517 32403 - Disclosure - NET SALES (Tables) Network

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518 Implied Table Table

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521 32503 - Disclosure - LONG-TERM INCENTIVE PLANS (Tables) Network

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526 Summary of stock options by exercise price Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsExplanatory
527 32603 - Disclosure - SEGMENT REPORTING (Tables) Network

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531 Schedule of company's geographic information classified according to the geographical region Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfGeographicalAreasExplanatory
532 32703 - Disclosure - INSURANCE (Tables) Network

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533 Implied Table Table

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535 Schedule of types of insurance Concept (Text Block (HTML)) For Period ifrs-full:DisclosureOfTypesOfInsuranceContractsExplanatory
536 32903 - Disclosure - EXPENSES BY NATURE (Tables) Network

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539 Schedule of expenses classified by nature Concept (Text Block (HTML)) For Period ggb:DisclosureOfExpensesByNatureTableTextBlock
540 33003 - Disclosure - FINANCIAL INCOME (Tables) Network

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544 40201 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES (Details) Network

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563 40202 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - New IFRS and Interpretations of the IFRIC (Details) Network

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603 40301 - Disclosure - CONSOLIDATED FINANCIAL STATEMENTS - Subsidiaries (Details) Network

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608 Gerdau Internacional Empreendimentos Ltda. - Grupo Gerdau Member ggb:GerdauInternacionalEmpreendimentosLtdaGrupoGerdauMember
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635 40302 - Disclosure - CONSOLIDATED FINANCIAL STATEMENTS - Joint ventures (Details) Network

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662 40304 - Disclosure - CONSOLIDATED FINANCIAL STATEMENTS - Gains and losses on assets held for sale and sale of interest in subsidiaries (Details) Network

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694 40401 - Disclosure - CASH AND CASH EQUIVALENTS, AND SHORT AND LONG-TERM INVESTMENTS (Details) Network

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695 Implied Table Table

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702 40501 - Disclosure - TRADE ACCOUNTS RECEIVABLE - Summary (Details) Network

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715 40502 - Disclosure - TRADE ACCOUNTS RECEIVABLE - Accounts receivable by aging (Details) Network

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716 Disclosure of financial assets [table] Table

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732 40503 - Disclosure - TRADE ACCOUNTS RECEIVABLE - Changes in allowance (Details) Network

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749 40601 - Disclosure - INVENTORIES - Components of inventory at net realizable value (Details) Network

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759 40602 - Disclosure - INVENTORIES - Changes in net realizable value of inventories (Details) Network

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760 Disclosure of fair value measurement of assets [table] Table

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768 Reversal of adjustment to net realizable value Concept (Monetary) For Period Debit ifrs-full:UnusedProvisionReversedOtherProvisions
769 Loss of control by selling of subsidiary Concept (Monetary) For Period Debit ggb:DecreaseThroughLossOfControlOfSubsidiaryAllowanceForInventoriesAdjustmentToNetRealizableValue
770 Loss of control by joint venture creation Concept (Monetary) For Period Debit ggb:DecreaseThroughLossOfControlOfJointVentureAllowanceForInventoriesAdjustmentToNetRealizableValue
771 Assets held for sale Concept (Monetary) For Period Debit ggb:DecreaseThroughTransferToAssetsClassifiedAsHeldForSaleAllowanceForInventoriesAdjustmentToNetRealizableValue
772 Exchange rate variation Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesOtherProvisions
773 Balance at the end of the year Concept (Monetary) As Of Credit ggb:AllowanceForInventoriesAdjustmentToNetRealizableValue
774 40701 - Disclosure - TAX CREDITS - Current and Non-current (Details) Network

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775 Disclosure of temporary difference, unused tax losses and unused tax credits [table] Table

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 ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
776 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
777 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
778 Tax credits Member ifrs-full:UnusedTaxCreditsMember
779 ICMS (state VAT) Member ggb:ICMSMember
780 Social security financing Member ggb:TaxCreditsSocialSecurityFinancingMember
781 Financing of social integration program Member ggb:TaxCreditsFinancingOfSocialIntegrationProgramMember
782 IPI (federal VAT) Member ggb:TaxCreditsFederalValueAddedTaxMember
783 IVA (Value-added tax) Member ggb:TaxCreditsValueAddedTaxMember
784 Others Member ggb:TaxCreditsOtherMember
785 Financing of social integration program and others Member ggb:TaxCreditsFinancingOfSocialIntegrationProgramAndOthersMember
786 Disclosure of Tax credits LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
787 Tax credits - current Concept (Monetary) As Of Debit ifrs-full:CurrentReceivablesFromTaxesOtherThanIncomeTax
788 Tax credits - non-current Concept (Monetary) As Of Debit ifrs-full:NoncurrentReceivablesFromTaxesOtherThanIncomeTax
789 Tax credits - current and non-current Concept (Monetary) As Of Debit ifrs-full:ReceivablesFromTaxesOtherThanIncomeTax
790 40702 - Disclosure - TAX CREDITS - Realization of non-current tax credits (Details) Network

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791 Disclosure of temporary difference, unused tax losses and unused tax credits [table] Table

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 ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
792 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
793 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
794 Tax credits Member ifrs-full:UnusedTaxCreditsMember
795 Maturity [axis] Axis ifrs-full:MaturityAxis
796 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
797 Year Two Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
798 Year Three Member ifrs-full:LaterThanTwoYearsAndNotLaterThanThreeYearsMember
799 After Year Three Member ifrs-full:LaterThanThreeYearsMember
800 Disclosure of temporary difference, unused tax losses and unused tax credits LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
801 Tax credits - non-current Concept (Monetary) As Of Debit ifrs-full:NoncurrentReceivablesFromTaxesOtherThanIncomeTax
802 40801 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES - Reconciliations of income and social contribution taxes at statutory rates to amounts presented in the Statement of Income (Details) Network

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803 Income tax disclosure [table] Table

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 ggb:IncomeTaxDisclosureTable
804 Range [axis] Axis ifrs-full:RangeAxis
805 Ranges [member] Member ifrs-full:RangesMember
806 Minimum Member ifrs-full:BottomOfRangeMember
807 Maximum Member ifrs-full:TopOfRangeMember
808 INCOME AND SOCIAL CONTRIBUTION TAXES LineItems ggb:IncomeTaxDisclosureLineItems
809 Applicable tax rate Concept (Percent) For Period ifrs-full:ApplicableTaxRate
810 Social contribution tax Concept (Percent) For Period ggb:ApplicableSocialContributionTaxRate
811 Tax rate for foreign subsidiaries Concept (Percent) For Period ifrs-full:TaxRateEffectOfForeignTaxRates
812 Tax rates for foreign subsidiaries mainly in financial activities Concept (Percent) For Period ggb:ApplicableTaxRatesForForeignSubsidiariesWithFinancialActivities
813 Reconciliations of taxes at statutory rates to amounts presented in the Statement of Income Abstract ifrs-full:ReconciliationOfAccountingProfitMultipliedByApplicableTaxRatesAbstract
814 Income (loss) before income taxes Concept (Monetary) For Period Credit ifrs-full:AccountingProfit
815 Statutory tax rates Concept (Percent) For Period ggb:ApplicableIncomeTaxAndSocialContributionTaxRate
816 Income and social contribution taxes at statutory rates Concept (Monetary) For Period Debit ifrs-full:TaxExpenseIncomeAtApplicableTaxRate
817 Tax adjustment with respect to: Abstract ggb:TaxAdjustmentsAbstract
818 Difference in tax rates in foreign companies Concept (Monetary) For Period Debit ifrs-full:TaxEffectOfForeignTaxRates
819 Equity in earnings of unconsolidated companies Concept (Monetary) For Period Credit ggb:TaxEffectOfEquityInEarningsLossesOfUnconsolidatedCompanies
820 Interest on equity Concept (Monetary) For Period Credit ggb:TaxEffectOfInterestOnEquity
821 Tax credits and incentives Concept (Monetary) For Period Credit ggb:TaxEffectOfTaxCreditsAndIncentives
822 Recognition of previously unrecognized tax losses Concept (Monetary) For Period Debit ggb:TaxEffectFromRecognitionOfPreviouslyUnrecognizedTaxLosses
823 Capital Gain Concept (Monetary) For Period Debit ggb:TaxEffectOfCapitalGainFromBusinessCombination
824 Other permanent differences, net Concept (Monetary) For Period Debit ifrs-full:OtherTaxEffectsForReconciliationBetweenAccountingProfitAndTaxExpenseIncome
825 Income and social contribution taxes Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
826 Current Concept (Monetary) For Period Debit ifrs-full:CurrentTaxExpenseIncome
827 Deferred Concept (Monetary) For Period Debit ifrs-full:DeferredTaxExpenseIncome
828 40802 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES - Changes in net deferred asset (liability) (Details) Network

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829 Disclosure of temporary difference, unused tax losses and unused tax credits [table] Table

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 ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsTable
830 Temporary difference, unused tax losses and unused tax credits [axis] Axis ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis
831 Temporary difference, unused tax losses and unused tax credits [member] Member ifrs-full:TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsMember
832 Tax loss carryforward Member ifrs-full:UnusedTaxLossesMember
833 Social contribution tax losses Member ggb:SocialContributionTaxLossesMember
834 Provision for tax, civil and labor liabilities Member ggb:ProvisionForTaxCivilAndLaborLiabilitiesMember
835 Benefits granted to employees Member ggb:BenefitsGrantedToEmployeesMember
836 Other temporary differences Member ifrs-full:OtherTemporaryDifferencesMember
837 Deferred exchange variance Member ifrs-full:UnrealisedForeignExchangeGainsLossesMember
838 Provision for losses Member ggb:ProvisionForLossesMember
839 Fair value adjustments on businesses acquired Member ggb:FairValueAdjustmentsOnBusinessesAcquiredMember
840 Deferred income and social contribution tax assets and liabilities at statutory tax rates LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
841 Breakdown and changes in deferred income and social contribution tax assets and liabilities at statutory tax rates Abstract ifrs-full:ReconciliationOfChangesInDeferredTaxLiabilityAssetAbstract
842 Balance as of beginning of period Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
843 Recognized in income Concept (Monetary) For Period ifrs-full:DeferredTaxExpenseIncomeRecognisedInProfitOrLoss
844 Effect of selling of subsidiary and others Concept (Monetary) For Period Credit ggb:IncreaseDecreaseThroughLossOfControlOfSubsidiaryAndOthersDeferredTaxLiabilityAsset
845 Others Concept (Monetary) For Period Credit ggb:IncreaseDecreaseThroughOtherChangesNotSeparatelyDisclosed
846 Comprehensive Income Concept (Monetary) For Period ifrs-full:IncomeTaxRelatingToComponentsOfOtherComprehensiveIncome
847 Balance as of end of period Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
848 40803 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES - Classification of net deferred asset (liability) (Details) Network

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849 Implied Table Table

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*

 implied:Table
850 INCOME AND SOCIAL CONTRIBUTION TAXES Abstract ifrs-full:MajorComponentsOfTaxExpenseIncomeAbstract
851 Total Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilityAsset
852 Non-current assets Concept (Monetary) As Of Debit ifrs-full:DeferredTaxAssets
853 Non-current liabilities Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilities
854 40804 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES - Estimated recovery and reversal of income and social contributions tax assets and liabilities (Details) Network

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855 Disclosure of temporary difference, unused tax losses and unused tax credits [table] Table

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856 Maturity [axis] Axis ifrs-full:MaturityAxis
857 Aggregated time bands [member] Member ifrs-full:AggregatedTimeBandsMember
858 Next 12 months Member ifrs-full:NotLaterThanOneYearMember
859 Year Two Member ifrs-full:LaterThanOneYearAndNotLaterThanTwoYearsMember
860 Year Three Member ifrs-full:LaterThanTwoYearsAndNotLaterThanThreeYearsMember
861 Year Four Member ifrs-full:LaterThanThreeYearsAndNotLaterThanFourYearsMember
862 After Year Four Member ggb:LaterThanFourYearsMember
863 Year Five Member ifrs-full:LaterThanFourYearsAndNotLaterThanFiveYearsMember
864 More than 5 years Member ifrs-full:LaterThanFiveYearsMember
865 Deferred income and social contribution tax assets and liabilities at statutory tax rates LineItems ifrs-full:DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
866 Non-current assets Concept (Monetary) As Of Debit ifrs-full:DeferredTaxAssets
867 Non-current liabilities Concept (Monetary) As Of Credit ifrs-full:DeferredTaxLiabilities
868 40805 - Disclosure - INCOME AND SOCIAL CONTRIBUTION TAXES - Unrecognized deferred income tax assets (Details) Network

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869 Income tax disclosure [table] Table

*

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 ggb:IncomeTaxDisclosureTable
870 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
871 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
872 Domestic Member ggb:SubsidiariesDomesticMember
873 Foreign Member ggb:SubsidiariesForeignMember
874 INCOME AND SOCIAL CONTRIBUTION TAXES LineItems ggb:IncomeTaxDisclosureLineItems
875 Unused tax losses for which no deferred tax asset recognised Concept (Monetary) As Of ifrs-full:UnusedTaxLossesForWhichNoDeferredTaxAssetRecognised
876 Unused tax credits for which no deferred tax asset recognised Concept (Monetary) As Of ifrs-full:UnusedTaxCreditsForWhichNoDeferredTaxAssetRecognised
877 40901 - Disclosure - INVESTMENTS IN ASSOCIATES AND JOINT VENTURES (Details) Network

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878 Disclosure Of Joint Ventures And Associates [Table] Table

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 ggb:DisclosureOfJointVenturesAndAssociatesTable
879 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
880 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
881 Gerdau Corsa S.A.P.I de C.V. Member ggb:GerdauCorsaSapiDeCvMember
882 Investment, Name [Axis] Axis srt:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
883 Investment, Name [Domain] Member srt:EquityMethodInvesteeNameDomain
884 Investments in North America Member ggb:InvestmentsInNorthAmericaMember
885 Investments in South America Member ggb:InvestmentsInSouthAmericaMember
886 Investments in Special Steel Member ggb:InvestmentsInSpecialSteelMember
887 Others Member ggb:OthersInvestmentsMember
888 INVESTMENTS IN ASSOCIATES AND JOINT VENTURES LineItems ggb:DisclosureOfJointVenturesAndAssociatesLineItems
889 Balance at beginning of period Concept (Monetary) As Of Debit ifrs-full:InvestmentAccountedForUsingEquityMethod
890 Equity in earnings Concept (Monetary) For Period Debit ggb:IncreaseDecreaseInInvestmentsInJointVenturesAndAssociatesShareOfProfitLoss
891 Cumulative Translation Adjustment Concept (Monetary) For Period Debit ggb:IncreaseDecreaseInInvestmentsInJointVenturesAndAssociatesExchangeDifferencesOnTranslationNetOfTax
892 Capital increase Concept (Monetary) For Period Debit ggb:IncreaseDecreaseInInvestmentsInJointVenturesAndAssociatesCapital
893 Joint venture creation Concept (Monetary) For Period Debit ggb:InvestmentInJointVenturesStartUpCosts
894 Contingent price complement Concept (Monetary) For Period Debit ggb:InvestmentsInAssociatesContingentConsiderationReceived
895 Effect of selling of subsidiary Concept (Monetary) For Period Credit ggb:DecreaseInInvestmentsInAssociatesEffectOfSaleOfSubsidiaryOfAssociateEntity
896 Dividends/Interest on equity Concept (Monetary) For Period Credit ggb:DecreaseInInvestmentsInJointVenturesAndAssociatesDividendsAndInterestOnEquityReceived
897 Balance at end of period Concept (Monetary) As Of Debit ifrs-full:InvestmentAccountedForUsingEquityMethod
898 Advance for future investment in joint venture Concept (Monetary) As Of Debit ggb:AdvanceForFutureInvestmentInJointVenture
899 41001 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Cost (Details) Network

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900 Disclosure of detailed information about property, plant and equipment [table] Table

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 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
901 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
902 Property, plant and equipment Member ifrs-full:PropertyPlantAndEquipmentMember
903 Land and buildings Member ifrs-full:LandAndBuildingsMember
904 Machines, equipment, and installations Member ifrs-full:MachineryMember
905 Data electronic equipment Member ggb:DataElectronicEquipmentMember
906 Property, plant and equipment under construction Member ifrs-full:ConstructionInProgressMember
907 Other Member ifrs-full:OtherPropertyPlantAndEquipmentMember
908 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
909 Carrying amount [member] Member ifrs-full:CarryingAmountMember
910 Gross Member ifrs-full:GrossCarryingAmountMember
911 PROPERTY, PLANT AND EQUIPMENT LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
912 Balance, beginning of period Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
913 Additions Concept (Monetary) For Period Debit ifrs-full:AdditionsOtherThanThroughBusinessCombinationsPropertyPlantAndEquipment
914 Capitalized interest Concept (Monetary) For Period ifrs-full:InterestCostsCapitalised
915 Transfers Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersPropertyPlantAndEquipment
916 Disposals Concept (Monetary) For Period Credit ifrs-full:DisposalsPropertyPlantAndEquipment
917 Loss of control by selling of subsidiary Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughLossOfControlOfSubsidiaryPropertyPlantAndEquipment
918 Impairment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
919 Transfer to assets held for sale Concept (Monetary) For Period Credit ggb:DecreaseThroughTransferToAssetsClassifiedAsHeldForSalePropertyPlantAndEquipment
920 Effects of IAS 29 adoption Concept (Monetary) For Period Debit ggb:IncreaseDecreaseThroughEffectsOfIas29AdoptionPropertyPlantAndEquipment
921 Foreign exchange effect Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesPropertyPlantAndEquipment
922 Balance, end of period Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
923 41002 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Accumulated Depreciation (Details) Network

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924 Disclosure of detailed information about property, plant and equipment [table] Table

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 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
925 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
926 Property, plant and equipment Member ifrs-full:PropertyPlantAndEquipmentMember
927 Land and buildings Member ifrs-full:LandAndBuildingsMember
928 Machines, equipment, and installations Member ifrs-full:MachineryMember
929 Data electronic equipment Member ggb:DataElectronicEquipmentMember
930 Property, plant and equipment under construction Member ifrs-full:ConstructionInProgressMember
931 Other Member ifrs-full:OtherPropertyPlantAndEquipmentMember
932 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
933 Carrying amount [member] Member ifrs-full:CarryingAmountMember
934 Accumulated depreciation Member ifrs-full:AccumulatedDepreciationAmortisationAndImpairmentMember
935 PROPERTY, PLANT AND EQUIPMENT LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
936 Balance, beginning of period Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
937 Depreciation Concept (Monetary) For Period ifrs-full:DepreciationPropertyPlantAndEquipment
938 Transfers Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughTransfersPropertyPlantAndEquipment
939 Disposals Concept (Monetary) For Period Credit ifrs-full:DisposalsPropertyPlantAndEquipment
940 Loss of control by selling of subsidiary Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughLossOfControlOfSubsidiaryPropertyPlantAndEquipment
941 Transfer to assets held for sale Concept (Monetary) For Period Credit ggb:DecreaseThroughTransferToAssetsClassifiedAsHeldForSalePropertyPlantAndEquipment
942 Effects of IAS 29 adoption Concept (Monetary) For Period Debit ggb:IncreaseDecreaseThroughEffectsOfIas29AdoptionPropertyPlantAndEquipment
943 Foreign exchange effect Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesPropertyPlantAndEquipment
944 Balance, end of period Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipment
945 41003 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Useful Lives (Details) Network

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 http://www.gerdau.com/role/DisclosurePropertyPlantAndEquipmentUsefulLivesDetails
946 Disclosure of detailed information about property, plant and equipment [table] Table

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 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
947 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
948 Property, plant and equipment Member ifrs-full:PropertyPlantAndEquipmentMember
949 Buildings Member ifrs-full:BuildingsMember
950 Machines, equipment, and installations Member ifrs-full:MachineryMember
951 Furniture and fixture Member ifrs-full:FixturesAndFittingsMember
952 Vehicles Member ifrs-full:VehiclesMember
953 Data electronic equipment Member ggb:DataElectronicEquipmentMember
954 Range [axis] Axis ifrs-full:RangeAxis
955 Ranges [member] Member ifrs-full:RangesMember
956 Minimum Member ifrs-full:BottomOfRangeMember
957 Maximum Member ifrs-full:TopOfRangeMember
958 PROPERTY, PLANT AND EQUIPMENT LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
959 Average rate of capitalized interest Concept (Percent) For Period ggb:AverageRateOfCapitalizedInterest
960 Useful lives of property, plant, and equipment Concept (xbrli:durationItemType) For Period ggb:UsefulLivesPropertyPlantAndEquipment
961 Amount of property, plant and equipment pledged as collateral for loans and financing Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipmentPledgedAsSecurity
962 41004 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Impairment (Details) Network

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963 Disclosure of detailed information about property, plant and equipment [table] Table

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*

 ifrs-full:DisclosureOfPropertyPlantAndEquipmentTable
964 Classes of property, plant and equipment [axis] Axis ifrs-full:ClassesOfPropertyPlantAndEquipmentAxis
965 Property, plant and equipment Member ifrs-full:PropertyPlantAndEquipmentMember
966 Land, buildings and construction Member ggb:LandBuildingsAndConstructionMember
967 Machines, equipment, and installations Member ifrs-full:MachineryMember
968 Property, plant and equipment under construction Member ifrs-full:ConstructionInProgressMember
969 PROPERTY, PLANT AND EQUIPMENT LineItems ifrs-full:DisclosureOfPropertyPlantAndEquipmentLineItems
970 Carrying value of impaired assets Concept (Monetary) As Of Debit ifrs-full:PropertyPlantAndEquipmentCarryingAmountOfRevaluedAssets
971 41101 - Disclosure - GOODWILL - Changes in Goodwill (Details) Network

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972 Disclosure of reconciliation of changes in goodwill [table] Table

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 ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillTable
973 Carrying amount, accumulated depreciation, amortisation and impairment and gross carrying amount [axis] Axis ifrs-full:CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis
974 Carrying amount [member] Member ifrs-full:CarryingAmountMember
975 Gross Member ifrs-full:GrossCarryingAmountMember
976 Accumulated impairment losses Member ifrs-full:AccumulatedImpairmentMember
977 Changes in goodwill LineItems ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillLineItems
978 Goodwill at beginning of period Concept (Monetary) As Of Debit ifrs-full:Goodwill
979 Foreign exchange effect Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesGoodwill
980 Impairment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossGoodwill
981 Effect of selling of subsidiary Concept (Monetary) For Period Credit ifrs-full:GoodwillDerecognisedWithoutHavingPreviouslyBeenIncludedInDisposalGroupClassifiedAsHeldForSale
982 Transfer to assets held for sale Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughClassifiedAsHeldForSaleGoodwill
983 Goodwill at end of period Concept (Monetary) As Of Debit ifrs-full:Goodwill
984 41102 - Disclosure - GOODWILL - Goodwill by segment (Details) Network

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985 Disclosure of reconciliation of changes in goodwill [table] Table

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986 Segments [axis] Axis ifrs-full:SegmentsAxis
987 Segments [member] Member ifrs-full:SegmentsMember
988 Brazil Member ggb:BrazilSegmentMember
989 Special Steel Member ggb:SpecialSteelSegmentMember
990 North America Member ggb:NorthAmericaSegmentMember
991 Goodwill by segment LineItems ifrs-full:DisclosureOfReconciliationOfChangesInGoodwillLineItems
992 Goodwill Concept (Monetary) As Of Debit ifrs-full:Goodwill
993 41201 - Disclosure - INTANGIBLE ASSETS - Changes in intangible assets by type (Details) Network

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994 Schedule of relationships recognized upon business combinations and software development, with application in the management of the business Table

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995 Classes of intangible assets other than goodwill [axis] Axis ifrs-full:ClassesOfIntangibleAssetsOtherThanGoodwillAxis
996 Intangible assets other than goodwill [member] Member ifrs-full:IntangibleAssetsOtherThanGoodwillMember
997 Supplier relationships Member ggb:SupplierRelationshipsMember
998 Software development Member ifrs-full:ComputerSoftwareMember
999 Customers contracts and relationships Member ifrs-full:CustomerrelatedIntangibleAssetsMember
1000 Others Member ifrs-full:OtherIntangibleAssetsMember
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1002 Ranges [member] Member ifrs-full:RangesMember
1003 Minimum Member ifrs-full:BottomOfRangeMember
1004 Maximum Member ifrs-full:TopOfRangeMember
1005 INTANGIBLE ASSETS LineItems ifrs-full:DisclosureOfIntangibleAssetsLineItems
1006 Other intangible assets at beginning of period Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
1007 Foreign exchange effect Concept (Monetary) For Period Debit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesIntangibleAssetsOtherThanGoodwill
1008 Acquisition Concept (Monetary) For Period Debit ifrs-full:AcquisitionsThroughBusinessCombinationsIntangibleAssetsOtherThanGoodwill
1009 Disposal Concept (Monetary) For Period Credit ifrs-full:DisposalsIntangibleAssetsOtherThanGoodwill
1010 Amortization Concept (Monetary) For Period ifrs-full:AmortisationIntangibleAssetsOtherThanGoodwill
1011 Effect of selling of subsidiary Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughLossOfControlOfSubsidiaryIntangibleAssetsOtherThanGoodwill
1012 Assets held for sale Concept (Monetary) For Period Credit ifrs-full:DecreaseThroughClassifiedAsHeldForSaleIntangibleAssetsOtherThanGoodwill
1013 Other intangible assets at end of period Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
1014 Estimated useful lives Concept (xbrli:durationItemType) For Period ggb:UsefulLivesIntangibleAssetsOtherThanGoodwill
1015 41202 - Disclosure - INTANGIBLE ASSETS - Intangible assets by segment (Details) Network

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1016 Schedule of relationships recognized upon business combinations and software development, with application in the management of the business Table

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 ifrs-full:DisclosureOfIntangibleAssetsTable
1017 Segments [axis] Axis ifrs-full:SegmentsAxis
1018 Segments [member] Member ifrs-full:SegmentsMember
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1020 Special Steel Member ggb:SpecialSteelSegmentMember
1021 South America Member ggb:SouthAmericaSegmentMember
1022 North America Member ggb:NorthAmericaSegmentMember
1023 Composition of other intangible assets by segment LineItems ifrs-full:DisclosureOfIntangibleAssetsLineItems
1024 Other Intangibles Concept (Monetary) As Of Debit ifrs-full:IntangibleAssetsOtherThanGoodwill
1025 41301 - Disclosure - LOANS AND FINANCING - Summary (Details) Network

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1026 Disclosure of detailed information about borrowings [table] Table

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 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
1027 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
1028 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
1029 Working capital Member ggb:WorkingCapitalMember
1030 Financing of property, plant and equipment and others Member ggb:FinancingOfPropertyPlantAndEquipmentAndOthersMember
1031 Ten/Thirty Year Bonds Member ggb:TenOrThirtyYearBondsMember
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1037 41302 - Disclosure - LOANS AND FINANCING - Principal and Interest (Details) Network

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*

 http://www.gerdau.com/role/DisclosureLoansAndFinancingPrincipalAndInterestDetails
1038 Implied Table Table

*

*

 implied:Table
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1043 41303 - Disclosure - LOANS AND FINANCING - By Currency (Details) Network

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*

 http://www.gerdau.com/role/DisclosureLoansAndFinancingByCurrencyDetails
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*

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 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
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1052 41304 - Disclosure - LOANS AND FINANCING - Amortization Schedule (Details) Network

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*

 http://www.gerdau.com/role/DisclosureLoansAndFinancingAmortizationScheduleDetails
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*

*

 ifrs-full:DisclosureOfMaturityAnalysisForNonderivativeFinancialLiabilitiesTable
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1065 41305 - Disclosure - LOANS AND FINANCING - Additional Disclosures (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureLoansAndFinancingAdditionalDisclosuresDetails
1066 Disclosure of detailed information about borrowings [table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
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1088 41401 - Disclosure - DEBENTURES - Summary (Details) Network

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*

 http://www.gerdau.com/role/DisclosureDebenturesSummaryDetails
1089 Disclosure of detailed information about borrowings [table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
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1105 41402 - Disclosure - DEBENTURES - Amortization schedules (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureDebenturesAmortizationSchedulesDetails
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*

*

 ifrs-full:DisclosureOfDetailedInformationAboutBorrowingsTable
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1126 41501 - Disclosure - FINANCIAL INSTRUMENTS - Fair value of financial instruments (Details) Network

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*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsFairValueOfFinancialInstrumentsDetails
1127 Disclosure of detailed information about financial instruments [table] Table

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*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
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1148 41502 - Disclosure - FINANCIAL INSTRUMENTS - Capital management risk (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsCapitalManagementRiskDetails
1149 Disclosure of objectives, policies and processes for managing capital [table] Table

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1161 41503 - Disclosure - FINANCIAL INSTRUMENTS - Liquidity risk (Details) Network

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*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsLiquidityRiskDetails
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*

*

 ifrs-full:DisclosureOfMaturityAnalysisForNonderivativeFinancialLiabilitiesTable
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1183 41504 - Disclosure - FINANCIAL INSTRUMENTS - Sensitivity analysis (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsSensitivityAnalysisDetails
1184 Disclosure of nature and extent of risks arising from financial instruments [table] Table

*

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 ifrs-full:DisclosureOfNatureAndExtentOfRisksArisingFromFinancialInstrumentsTable
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1205 41505 - Disclosure - FINANCIAL INSTRUMENTS - Financial instruments per category (Details) Network

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*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsFinancialInstrumentsPerCategoryDetails
1206 Disclosure of detailed information about financial instruments [table] Table

*

*

 ifrs-full:DisclosureOfFinancialInstrumentsTable
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1238 41506 - Disclosure - FINANCIAL INSTRUMENTS - Swap Contracts (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsSwapContractsDetails
1239 Disclosure of detailed information about hedging instruments [table] Table

*

*

 ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsTable
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1263 41507 - Disclosure - FINANCIAL INSTRUMENTS - Prospective and retrospective tests (Details) Network

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*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsProspectiveAndRetrospectiveTestsDetails
1264 Disclosure of detailed information about financial instruments [table] Table

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 ifrs-full:DisclosureOfFinancialInstrumentsTable
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1285 41508 - Disclosure - FINANCIAL INSTRUMENTS - Net investment hedge (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsNetInvestmentHedgeDetails
1286 Disclosure of detailed information about hedging instruments [table] Table

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*

 ifrs-full:DisclosureOfDetailedInformationAboutHedgingInstrumentsTable
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1300 41509 - Disclosure - FINANCIAL INSTRUMENTS - Measurement of fair value (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureFinancialInstrumentsMeasurementOfFairValueDetails
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 ifrs-full:DisclosureOfFinancialInstrumentsTable
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1333 41510 - Disclosure - FINANCIAL INSTRUMENTS - Changes in liabilities from Cash Flow from financing activities (Details) Network

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 http://www.gerdau.com/role/DisclosureFinancialInstrumentsChangesInLiabilitiesFromCashFlowFromFinancingActivitiesDetails
1334 Disclosure of reconciliation of liabilities arising from financing activities [table] Table

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*

 ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesTable
1335 Liabilities arising from financing activities [axis] Axis ifrs-full:LiabilitiesArisingFromFinancingActivitiesAxis
1336 Liabilities arising from financing activities [member] Member ifrs-full:LiabilitiesArisingFromFinancingActivitiesMember
1337 Related parties, net Member ifrs-full:AssetsHeldToHedgeLiabilitiesArisingFromFinancingActivitiesMember
1338 Debt, Debentures And Losses/Gains On Financial Instruments, Net Member ggb:DebtDebenturesAndLossesGainsOnFinancialInstrumentsNetMember
1339 Changes in liabilities from Cash flow from financing activities LineItems ifrs-full:DisclosureOfReconciliationOfLiabilitiesArisingFromFinancingActivitiesLineItems
1340 Beginning of year Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
1341 Cash transactions Abstract ggb:ChangesInLiabilitiesArisingFromFinancingActivitiesCashTransactionsAbstract
1342 Proceeds/(Repayment) from financing activities Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughFinancingCashFlowsLiabilitiesArisingFromFinancingActivities
1343 Interest paid on loans and financing Concept (Monetary) For Period Debit ggb:DecreaseThroughInterestPaidOnLoansAndFinancing
1344 Non cash transactions Abstract ggb:ChangesInLiabilitiesArisingFromFinancingActivitiesNonCashTransactionsAbstract
1345 Interest expense on loans and Interest on loans with related parties Concept (Monetary) For Period Credit ggb:IncreaseThroughInterestExpenseIncurredButNotYetPaid
1346 Exchange variation, operations with subsidiaries and associate company and others Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughEffectOfChangesInForeignExchangeRatesLiabilitiesArisingFromFinancingActivities
1347 End of year Concept (Monetary) As Of Credit ifrs-full:LiabilitiesArisingFromFinancingActivities
1348 41601 - Disclosure - TAXES PAYABLE (Details) Network

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*

 http://www.gerdau.com/role/DisclosureTaxesPayableDetails
1349 Implied Table Table

*

*

 implied:Table
1350 TAXES PAYABLE Abstract ggb:TaxesPayableAbstract
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1352 ICMS (state VAT) Concept (Monetary) As Of Credit ggb:StateValueAddedTaxCurrentTaxesPayable
1353 COFINS (tax on revenue) Concept (Monetary) As Of Credit ggb:TaxOnRevenueCurrentTaxesPayable
1354 IPI (federal VAT) Concept (Monetary) As Of Credit ggb:FederalValueAddedTaxCurrentTaxesPayable
1355 IVA (value-added tax) and others Concept (Monetary) As Of Credit ggb:ValueAddedTaxAndOthersCurrentTaxesPayable
1356 Taxes payable Concept (Monetary) As Of Credit ifrs-full:CurrentTaxLiabilitiesCurrent
1357 41701 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Provisions (Details) Network

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*

 http://www.gerdau.com/role/DisclosureTaxCivilAndLaborClaimsAndContingentAssetsProvisionsDetails
1358 Disclosure of other provisions [table] Table

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*

 ifrs-full:DisclosureOfOtherProvisionsTable
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1364 Civil provisions Member ggb:CivilProvisionsMember
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1368 Reversal of interest on provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:FinancialIncomeFromReversalOfContingentTaxLiabilities
1369 Judicial deposits, ICMS legal proceeding Concept (Monetary) As Of Debit ggb:JudicialDepositLegalProceedingsICMS
1370 41702 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Changes in Provisions (Details) Network

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*

 http://www.gerdau.com/role/DisclosureTaxCivilAndLaborClaimsAndContingentAssetsChangesInProvisionsDetails
1371 Disclosure of other provisions [table] Table

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*

 ifrs-full:DisclosureOfOtherProvisionsTable
1372 Classes of other provisions [axis] Axis ifrs-full:ClassesOfProvisionsAxis
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1374 Legal proceedings provision Member ifrs-full:LegalProceedingsProvisionMember
1375 Other provisions disclosures LineItems ifrs-full:DisclosureOfOtherProvisionsLineItems
1376 Changes in the tax, labor and civil provisions : Abstract ifrs-full:ReconciliationOfChangesInOtherProvisionsAbstract
1377 Balance at the beginning of the year Concept (Monetary) As Of Credit ifrs-full:LongtermLegalProceedingsProvision
1378 Additions Concept (Monetary) For Period Credit ifrs-full:AdditionalProvisionsOtherProvisions
1379 Monetary correction Concept (Monetary) For Period Credit ggb:IncreaseDecreaseThroughMonetaryVariationOtherProvisions
1380 Reversal of contingent liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalNet
1381 Reversal of interest on provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:FinancialIncomeFromReversalOfContingentTaxLiabilities
1382 Reversal of accrued amounts Concept (Monetary) For Period Debit ifrs-full:UnusedProvisionReversedOtherProvisions
1383 Foreign exchange effect on provisions in foreign currency Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughNetExchangeDifferencesOtherProvisions
1384 Loss of control by joint venture creation Concept (Monetary) For Period Debit ggb:DecreaseThroughLossOfControlByJointVentureCreationOtherProvisions
1385 Balance at the end of the year Concept (Monetary) As Of Credit ifrs-full:LongtermLegalProceedingsProvision
1386 41703 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Tax contingencies (Details) Network

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*

 http://www.gerdau.com/role/DisclosureTaxCivilAndLaborClaimsAndContingentAssetsTaxContingenciesDetails
1387 Disclosure of contingent liabilities [table] Table

*

*

 ifrs-full:DisclosureOfContingentLiabilitiesTable
1388 Classes of contingent liabilities [axis] Axis ifrs-full:ClassesOfContingentLiabilitiesAxis
1389 Contingent liabilities [member] Member ifrs-full:ContingentLiabilitiesMember
1390 Tax contingencies Member ifrs-full:TaxContingentLiabilityMember
1391 Litigation Case [Axis] Axis srt:LitigationCaseAxis
1392 Litigation Case [Domain] Member srt:LitigationCaseTypeDomain
1393 Credit rights and rate differences Member ggb:CreditRightsAndRateDifferencesMember
1394 IPI credit on inputs Member ggb:CreditsOnInputsMember
1395 Non-approval of compensation of credits on inputs Member ggb:NonApprovalOfCompensationOfCreditsOnInputsMember
1396 Social security contributions Member ggb:SocialSecurityContributionsMember
1397 Other Taxes Member ggb:OtherTaxesMember
1398 Withholding Income Tax Member ggb:WithholdingIncomeTaxMember
1399 Corporate Income Tax and Social Contribution Tax Member ggb:CorporateIncomeTaxAndSocialContributionTaxMember
1400 Goodwill Deductibility Member ggb:GoodwillDeductibilityMember
1401 IFRS Litigation Status [Axis] Axis ggb:IfrsLitigationStatusAxis
1402 IFRS Litigation Status [Domain] Member ggb:IfrsLitigationStatusDomain
1403 Pending Member ggb:IfrsPendingLitigationMember
1404 Voluntary Appeal Partially Granted Member ggb:VoluntaryAppealPartiallyGrantedMember
1405 Special appeal filed Member ggb:SpecialAppealMember
1406 Administrative collection Member ggb:AdministrativeCollectionMember
1407 Voluntary Appeal Dismissed Member ggb:VoluntaryAppealDismissedMember
1408 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1409 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1410 Gerdau Acos Longos S.A. and Gerdau Acominas S.A. Member ggb:GerdauAcosLongosS.a.AndGerdauAcominasS.a.Member
1411 Gerdau Acos Longos S.A. Member ggb:GerdauAcosLongosSaMember
1412 Gerdau Internacional Empreendimentos Ltda. and Gerdau Acos Especiais S.A Member ggb:GerdauInternacionalEmpreendimentosLtda.AndGerdauAcosEspeciaisS.a.Member
1413 Gerdau Internacional Empreendimentos Ltda Member ggb:GerdauInternacionalEmpreendimentosLtdaMember
1414 Gerdau Acominas S.A., Gerdau Acos Longos S.A., and Gerdau Acos Especiais S.A. Member ggb:GerdauAcominasSaGerdauAcosLongosSaAndGerdauAcosEspeciaisSaMember
1415 Gerdau Acos Especiais S.A. Member ggb:GerdauAcosEspeciaisSaMember
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1417 Estimated financial effect of contingent liabilities Concept (Monetary) As Of ifrs-full:EstimatedFinancialEffectOfContingentLiabilities
1418 Number of proceedings Concept (Integer) As Of ggb:IfrsLossContingencyPendingClaimsNumber
1419 Remaining tax Contingency liability from a notice Concept (Monetary) As Of Credit ggb:AmountOfTaxContingencyLiabilityRemainingFromNotice
1420 41704 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Civil Contingencies and Administrative proceedings (Details) Network

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*

 http://www.gerdau.com/role/DisclosureTaxCivilAndLaborClaimsAndContingentAssetsCivilContingenciesAndAdministrativeProceedingsDetails
1421 Disclosure of contingent liabilities [table] Table

*

*

 ifrs-full:DisclosureOfContingentLiabilitiesTable
1422 Classes of contingent liabilities [axis] Axis ifrs-full:ClassesOfContingentLiabilitiesAxis
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1425 Administrative proceedings contingencies Member ggb:AdministrativeProceedingsContingenciesMember
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1427 Litigation Case [Domain] Member srt:LitigationCaseTypeDomain
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1429 Other Demands Of a Civil Nature Member ggb:OtherDemandsOfCivilNatureMember
1430 Business combinations [axis] Axis ifrs-full:BusinessCombinationsAxis
1431 Entity's total for business combinations [member] Member ifrs-full:EntitysTotalForBusinessCombinationsMember
1432 Gerdau Acos Longos S.A. Member ggb:GerdauAcosLongosSaMember
1433 Gerdau Acominas S.A. and subsidiary Member ggb:GerdauAcominasS.A.Member
1434 Gerdau Acos Especiais S.A. Member ggb:GerdauAcosEspeciaisSaMember
1435 Gerdau America Latina Participacoes S.A. Member ggb:GerdauAmericaLatinaParticipacoesSaMember
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1437 Estimated financial effect of contingent liabilities Concept (Monetary) As Of ifrs-full:EstimatedFinancialEffectOfContingentLiabilities
1438 Number of civil construction unions Concept (Integer) For Period ggb:NumberOfCivilConstructionUnions
1439 Fine for existence of cartel on gross revenues (in percentage) Concept (Percent) For Period ggb:FineForExistenceOfCartelOnGrossRevenues
1440 Fine for existence of cartel Concept (Monetary) For Period Credit ggb:FineForExistenceOfCartel
1441 Fine for existence of cartel updated by judicial accounting Concept (Monetary) For Period Credit ggb:FineForExistenceOfCartelUpdatedByJudicialAccounting
1442 Number of lawsuits that challenged the investigation Concept (Integer) For Period ggb:NumberOfLawsuitsChallengedInvestigation
1443 Administrative proceedings disclosures Abstract ggb:AdministrativeProceedingsAbstract
1444 Percentage of voting equity interests acquired Concept (Percent) As Of ifrs-full:PercentageOfVotingEquityInterestsAcquired
1445 41705 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Judicial Deposits (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureTaxCivilAndLaborClaimsAndContingentAssetsJudicialDepositsDetails
1446 Implied Table Table

*

*

 implied:Table
1447 TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS Abstract ggb:DisclosureOfTaxCivilAndLaborClaimsAndContingentAssetsAbstract
1448 Tax Concept (Monetary) As Of Debit ggb:NoncurrentTaxRelatedRestrictedCashAndCashEquivalents
1449 Labor Concept (Monetary) As Of Debit ggb:NoncurrentLaborRelatedRestrictedCashAndCashEquivalents
1450 Civil Concept (Monetary) As Of Debit ggb:NoncurrentCivilRelatedRestrictedCashAndCashEquivalents
1451 Judicial deposits Concept (Monetary) As Of Debit ifrs-full:NoncurrentRestrictedCashAndCashEquivalents
1452 41706 - Disclosure - TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS - Contingent Assets (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureTaxCivilAndLaborClaimsAndContingentAssetsContingentAssetsDetails
1453 Implied Table Table

*

*

 implied:Table
1454 TAX, CIVIL AND LABOR CLAIMS AND CONTINGENT ASSETS Abstract ggb:DisclosureOfTaxCivilAndLaborClaimsAndContingentAssetsAbstract
1455 Minimum industrial consumers monthly electricity consumption limit (in Kilo watt hour) Concept (num:powerItemType) For Period ggb:MinimumIndustrialConsumersMonthlyElectricityConsumptionLimit
1456 Maximum period to return the compulsory loan to taxpayers Concept (xbrli:durationItemType) For Period ggb:MaximumPeriodForReturningOfCompulsoryLoan
1457 Claims receivable from monetary correction of principal, interest, moratory and others due to compulsory loans Concept (Monetary) For Period Debit ggb:ClaimsReceivableFromMonetaryCorrectionOfPrincipalInterestMoratoryAndOthers
1458 41801 - Disclosure - RELATED-PARTY TRANSACTIONS - Intercompany loans (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureRelatedPartyTransactionsIntercompanyLoansDetails
1459 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
1460 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1461 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1462 Gerdau Corsa S.A.P.I de C.V. Member ggb:GerdauCorsaSapiDeCvMember
1463 Fundacao Gerdau Member ggb:FundacaoGerdauMember
1464 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
1465 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
1466 Diaco S.A. Member ggb:DiacoSaMember
1467 RELATED PARTY TRANSACTIONS LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
1468 Assets Concept (Monetary) As Of Debit ifrs-full:NoncurrentReceivablesDueFromRelatedParties
1469 Liabilities Concept (Monetary) As Of Credit ifrs-full:NoncurrentPayablesToRelatedParties
1470 Net financial income Concept (Monetary) For Period Credit ggb:InterestIncomeExpenseOnLoansWithRelatedParties
1471 41802 - Disclosure - RELATED-PARTY TRANSACTIONS - Operations with related parties (Details) Network

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*

 http://www.gerdau.com/role/DisclosureRelatedPartyTransactionsOperationsWithRelatedPartiesDetails
1472 Disclosure of transactions between related parties [table] Table

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*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
1473 Classes of assets [axis] Axis ifrs-full:ClassesOfAssetsAxis
1474 Assets [member] Member ifrs-full:ClassesOfAssetsMember
1475 Investments Member ifrs-full:InvestmentsAccountedForUsingEquityMethodMember
1476 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1477 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1478 Controlling shareholders Member ggb:ControllingShareholdersMember
1479 RELATED PARTY TRANSACTIONS LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
1480 Sales to Related parties Concept (Monetary) For Period Credit ifrs-full:RevenueFromSaleOfGoodsRelatedPartyTransactions
1481 Purchases from related parties Concept (Monetary) For Period Debit ifrs-full:PurchasesOfGoodsRelatedPartyTransactions
1482 Net amount, related party transactions Concept (Monetary) For Period Credit ggb:NetRevenuePurchasesFromTransactionsWithRelatedParties
1483 Guarantee fee percentage Concept (Percent) For Period ggb:DebentureGuaranteeFeePercentage
1484 Debenture guarantee fees Concept (Monetary) For Period Debit ggb:DebentureGuaranteeFees
1485 Revenue from rental agreement Concept (Monetary) For Period Credit ggb:RevenueFromRentalAgreementWithRelatedParty
1486 41803 - Disclosure - RELATED-PARTY TRANSACTIONS - Operations with related parties, guarantees granted (Details) Network

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*

 http://www.gerdau.com/role/DisclosureRelatedPartyTransactionsOperationsWithRelatedPartiesGuaranteesGrantedDetails
1487 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
1488 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1489 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1490 Joint-venture Member ifrs-full:JointVenturesWhereEntityIsVenturerMember
1491 Subsidiary and Joint-venture Member ggb:SubsidiariesAndJointVenturesMember
1492 Subsidiaries [axis] Axis ifrs-full:SignificantInvestmentsInSubsidiariesAxis
1493 Entity's total for subsidiaries [member] Member ifrs-full:EntitysTotalForSubsidiariesMember
1494 Gerdau Metaldom S.A; Aceros Corsa S.A De C.V Member ggb:GerdauMetaldomS.aAndAcerosCorsaS.aDeC.vMember
1495 Joint ventures [axis] Axis ifrs-full:JointVenturesAxis
1496 Entity's total for joint ventures [member] Member ifrs-full:EntitysTotalForJointVenturesMember
1497 Diaco S.A. Member ggb:DiacoSaMember
1498 Gerdau Corsa S.A.P.I de C.V. Member ggb:GerdauCorsaSapiDeCvMember
1499 Gerdau Summit Aos Fundidos e Forjados S.A. Member ggb:GerdauSummitAcosFundidosEForjadosSaMember
1500 Borrowings by name [axis] Axis ifrs-full:BorrowingsByNameAxis
1501 Borrowings by name [member] Member ifrs-full:BorrowingsByNameMember
1502 Financing Agreements Member ggb:FinancingAgreementsMember
1503 RELATED PARTY TRANSACTIONS LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
1504 Guarantees granted Abstract ggb:GuaranteesGrantedAbstract
1505 Original Amount Concept (Monetary) For Period ifrs-full:ProvisionOfGuaranteesOrCollateralByEntityRelatedPartyTransactions
1506 Carrying Amount Concept (Monetary) As Of Credit ifrs-full:OutstandingCommitmentsMadeByEntityRelatedPartyTransactions
1507 41804 - Disclosure - RELATED-PARTY TRANSACTIONS - Debentures (Details) Network

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*

 http://www.gerdau.com/role/DisclosureRelatedPartyTransactionsDebenturesDetails
1508 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
1509 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1510 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1511 Direct or indirect shareholders Member ggb:DirectOrIndirectShareholdersMember
1512 RELATED PARTY TRANSACTIONS LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
1513 Debentures held Concept (Monetary) As Of Debit ifrs-full:DebtInstrumentsHeld
1514 Number of debentures held Concept (Decimal) As Of ggb:NumberOfDebtInstrumentsHeld
1515 41805 - Disclosure - RELATED-PARTY TRANSACTIONS - Key Management compensation (Details) Network

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*

 http://www.gerdau.com/role/DisclosureRelatedPartyTransactionsKeyManagementCompensationDetails
1516 Disclosure of transactions between related parties [table] Table

*

*

 ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesTable
1517 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1518 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1519 Key Management personnel Member ifrs-full:KeyManagementPersonnelOfEntityOrParentMember
1520 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
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1522 Stock options Member ggb:IfrsEmployeeStockOptionMember
1523 Restricted shares Member ggb:IfrsRestrictedStockMember
1524 RELATED PARTY TRANSACTIONS LineItems ifrs-full:DisclosureOfTransactionsBetweenRelatedPartiesLineItems
1525 Key management salaries, variable compensation and benefits Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensation
1526 Contributions to defined contribution pension plans Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationPostemploymentBenefits
1527 Long term incentive plan attributable to key management Concept (Monetary) For Period Debit ifrs-full:KeyManagementPersonnelCompensationSharebasedPayment
1528 Stock options granted to Management Abstract ggb:StockOptionsGrantedToKeyManagementPersonnelAbstract
1529 Number of shares Abstract ggb:StockOptionsNumberOfSharesAbstract
1530 Balance, beginning of year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
1531 Options Cancelled Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsForfeitedInSharebasedPaymentArrangement
1532 Balance, end of year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
1533 Weighted exercise price Abstract ggb:WeightedAverageExercisePriceAbstract
1534 Beginning of year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1535 Options Cancelled Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsForfeitedInSharebasedPaymentArrangement
1536 End of year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1537 Restricted shares granted to Management Abstract ggb:RestrictedSharesGrantedToKeyManagementPersonnelAbstract
1538 Balance, beginning of year Concept (Decimal) As Of ifrs-full:NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
1539 Granted Concept (Decimal) For Period ifrs-full:NumberOfInstrumentsOtherEquityInstrumentsGranted
1540 Exercised Concept (Decimal) For Period ifrs-full:NumberOfOtherEquityInstrumentsExercisedOrVestedInSharebasedPaymentArrangement
1541 Shares adjustment Concept (Decimal) For Period ggb:NumberOfOtherEquityInstrumentsSharesAdjustmentInShareBasedPaymentArrangement
1542 Balance, end of year Concept (Decimal) As Of ifrs-full:NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
1543 41901 - Disclosure - EMPLOYEE BENEFITS - Summary (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsSummaryDetails
1544 Disclosure Of Employee Benefit Plans [Table] Table

*

*

 ggb:DisclosureOfEmployeeBenefitPlansTable
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1548 Defined benefit pension plan Member ggb:DefinedBenefitPensionPlanMember
1549 Post-employment health care benefit Member ggb:PostEmploymentHealthCareBenefitMember
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1553 Total liabilities Concept (Monetary) As Of Credit ifrs-full:ProvisionsForEmployeeBenefits
1554 Current Concept (Monetary) As Of Credit ifrs-full:CurrentProvisionsForEmployeeBenefits
1555 Non-current Concept (Monetary) As Of Credit ifrs-full:NoncurrentProvisionsForEmployeeBenefits
1556 41902 - Disclosure - EMPLOYEE BENEFITS - Post-employment defined benefit pension plan (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentDefinedBenefitPensionPlanDetails
1557 Disclosure of defined benefit plans [table] Table

*

*

 ifrs-full:DisclosureOfDefinedBenefitPlansTable
1558 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1559 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1560 Post-employment defined benefit pension plans Member ggb:PostEmploymentDefinedBenefitPensionPlanMember
1561 North-American defined benefit plans Member ggb:NorthAmericanPostEmploymentDefinedBenefitPensionPlanMember
1562 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
1563 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
1564 Discount rate Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
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1566 Increase in actuarial assumption (as a percent) Concept (Percent) As Of ifrs-full:PercentageOfReasonablyPossibleIncreaseInActuarialAssumption
1567 Decrease in actuarial assumption (as a percent) Concept (Percent) As Of ifrs-full:PercentageOfReasonablyPossibleDecreaseInActuarialAssumption
1568 Increase (decrease) in defined benefit obligation due to increase in actuarial assumption Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleIncreaseInActuarialAssumption
1569 Increase (decrease) in defined benefit obligation due to decrease in actuarial assumption Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleDecreaseInActuarialAssumption
1570 Accumulated other comprehensive income Concept (Monetary) As Of Credit ifrs-full:AccumulatedOtherComprehensiveIncome
1571 41903 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Current expenses (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanCurrentExpensesDetails
1572 Disclosure of net defined benefit liability (asset) [table] Table

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*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1573 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
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1575 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1576 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1577 Current expenses of the defined benefit pension plans Abstract ggb:CurrentExpensesOfDefinedBenefitPensionPlansAbstract
1578 Cost of current service Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
1579 Interest expense Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
1580 Return on plan assets Concept (Monetary) For Period Debit ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
1581 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
1582 Settlement Concept (Monetary) For Period Debit ifrs-full:GainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
1583 Interest cost on unrecoverable surplus Concept (Monetary) For Period Credit ggb:InterestCostOnUnrecoverableSurplusArisingFromNetDefinedBenefitLiabilityAsset
1584 Net pension cost (benefit) Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInNetDefinedBenefitLiabilityAsset
1585 41904 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Reconciliation of plan assets and liabilities (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanReconciliationOfPlanAssetsAndLiabilitiesDetails
1586 Disclosure of net defined benefit liability (asset) [table] Table

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*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1587 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1588 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1589 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1590 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1591 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1592 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1593 Plan assets Member ifrs-full:PlanAssetsMember
1594 Asset ceiling restrictions on recognition of net funded assets Member ifrs-full:EffectOfAssetCeilingMember
1595 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1596 Reconciliations of assets and liabilities of the plans Abstract ggb:ReconciliationsOfPlanAssetsAndLiabilitiesAbstract
1597 Net Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1598 Defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
1599 41905 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Variation of the plan obligations (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanVariationOfPlanObligationsDetails
1600 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1601 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1602 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1603 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1604 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1605 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1606 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1607 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1608 Obligation at the beginning of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1609 Cost of service Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
1610 Interest expense Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
1611 Payment of benefits Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
1612 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
1613 Supplementary amounts of the plan Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughOtherChangesNetDefinedBenefitLiabilityAsset
1614 Settlement Concept (Monetary) For Period Debit ifrs-full:PaymentsInRespectOfSettlementsNetDefinedBenefitLiabilityAsset
1615 Gain (loss) on remeasurement Concept (Monetary) For Period Debit ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAsset
1616 Liabilities held for sale Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughBusinessCombinationsAndDisposalsNetDefinedBenefitLiabilityAsset
1617 Exchange Variance Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangesInForeignExchangeRatesNetDefinedBenefitLiabilityAsset
1618 Obligation at the end of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1619 41906 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Variation of the plan assets (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanVariationOfPlanAssetsDetails
1620 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1621 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1622 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1623 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1624 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1625 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1626 Plan assets Member ifrs-full:PlanAssetsMember
1627 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1628 Fair value of the plan assets at the beginning of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1629 Return of the plan assets Concept (Monetary) For Period Debit ifrs-full:ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
1630 Contributions from sponsors Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
1631 Settlement Concept (Monetary) For Period Debit ifrs-full:PaymentsInRespectOfSettlementsNetDefinedBenefitLiabilityAsset
1632 Payment of benefits Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
1633 Remeasurement Concept (Monetary) For Period Debit ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAsset
1634 Assets held for sale Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughBusinessCombinationsAndDisposalsNetDefinedBenefitLiabilityAsset
1635 Exchange Variance Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangesInForeignExchangeRatesNetDefinedBenefitLiabilityAsset
1636 Fair value of plan assets at the end of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1637 Value of shares included in fair value of plan assets Concept (Monetary) As Of Debit ggb:DescriptionOfAmountsOfEntitysOwnSharesIncludedInFairValueOfPlanAssets
1638 41907 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Actuarial gains and losses (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanActuarialGainsAndLossesDetails
1639 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1640 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1641 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1642 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1643 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1644 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1645 Plan assets Member ifrs-full:PlanAssetsMember
1646 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1647 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1648 Amounts recognized as actuarial gains and losses in the statement of comprehensive income Abstract ggb:AmountsRecognizedAsActuarialGainsAndLossesInStatementOfComprehensiveIncomeAbstract
1649 Gain (loss) on remeasurement Concept (Monetary) For Period Debit ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAsset
1650 Restriction recognized in Other Comprehensive Income Concept (Monetary) For Period Credit ggb:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRestrictionsOfDefinedBenefitPlans
1651 Remeasurements recognized in Other Comprehensive Income Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
1652 41908 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Historical actuarial remeasurements (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanHistoricalActuarialRemeasurementsDetails
1653 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1654 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1655 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1656 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1657 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1658 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1659 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1660 Plan assets Member ifrs-full:PlanAssetsMember
1661 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1662 Historical actuarial remeasurements Abstract ggb:HistoricalActuarialRemeasurementsAbstract
1663 Present value of defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:DefinedBenefitObligationAtPresentValue
1664 Fair value of plan assets Concept (Monetary) As Of Debit ifrs-full:PlanAssetsAtFairValue
1665 Surplus (Deficit) Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
1666 Experience adjustments on plan liabilities Concept (Monetary) For Period Debit ggb:ActuarialGainsLossesArisingFromExperienceAdjustmentsOnDefinedBenefitLiabilities
1667 Experience adjustments on plan assets Concept (Monetary) For Period Credit ggb:ActuarialGainsLossesArisingFromExperienceAdjustmentsOnPlanAssets
1668 41909 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Allocation of plan assets (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanAllocationOfPlanAssetsDetails
1669 Disclosure of fair value of plan assets [table] Table

*

*

 ifrs-full:DisclosureOfFairValueOfPlanAssetsTable
1670 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1671 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1672 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1673 Geographical [Axis] Axis srt:StatementGeographicalAxis
1674 Geographical [Domain] Member srt:SegmentGeographicalDomain
1675 Brazil Member country:BR
1676 North America Member srt:NorthAmericaMember
1677 Disclosure of fair value of plan assets [line items] LineItems ifrs-full:DisclosureOfFairValueOfPlanAssetsLineItems
1678 Allocation for plan assets Abstract ggb:AllocationForPlanAssetsAbstract
1679 Fixed income Concept (Percent) For Period ggb:AllocationForPlanFixedIncomePercentage
1680 Variable income Concept (Percent) For Period ggb:AllocationForPlanVariableIncomePercentage
1681 Others Concept (Percent) For Period ggb:AllocationForPlanOthersPercentage
1682 Total Concept (Percent) For Period ggb:AllocationForPlanPercentage
1683 Target allocation of shares (as a percent) Concept (Percent) For Period ggb:AllocationForPlanAllocationRangeForSharesPercentage
1684 Target allocation of debt securities (as a percent) Concept (Percent) For Period ggb:AllocationForPlanAllocationRangeForDebtSecuritiesPercentage
1685 Target allocation of alternative securities (as a percent) Concept (Percent) For Period ggb:AllocationForPlanAllocationRangeForAlternativeSecuritiesPercentage
1686 41910 - Disclosure - EMPLOYEE BENEFITS - Defined benefit pension plan - Assumptions used to calculate defined benefit plans (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsDefinedBenefitPensionPlanAssumptionsUsedToCalculateDefinedBenefitPlansDetails
1687 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1688 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1689 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1690 Defined benefit pension plan Member ifrs-full:DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
1691 Geographical [Axis] Axis srt:StatementGeographicalAxis
1692 Geographical [Domain] Member srt:SegmentGeographicalDomain
1693 Brazil Member country:BR
1694 North America Member srt:NorthAmericaMember
1695 Range [axis] Axis ifrs-full:RangeAxis
1696 Ranges [member] Member ifrs-full:RangesMember
1697 Minimum Member ifrs-full:BottomOfRangeMember
1698 Maximum Member ifrs-full:TopOfRangeMember
1699 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1700 Summary of assumptions used to calculate the defined benefit plans Abstract ggb:SummaryOfAssumptionsUsedToCalculateDefinedBenefitPlansAbstract
1701 Average discount rate Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfDiscountRates
1702 Rate of increase in compensation Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfExpectedRatesOfSalaryIncreases
1703 41911 - Disclosure - EMPLOYEE BENEFITS - Post-employment defined contribution pension plan (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentDefinedContributionPensionPlanDetails
1704 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1705 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1706 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1707 Defined contribution pension plan Member ggb:DefinedContributionPensionPlanMember
1708 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1709 Total cost Concept (Monetary) For Period Debit ifrs-full:PostemploymentBenefitExpenseDefinedContributionPlans
1710 41912 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Net periodic costs (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanNetPeriodicCostsDetails
1711 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1712 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1713 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1714 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1715 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1716 Net periodic costs of post-employment health care benefits Abstract ggb:NetPeriodicCostsOfPostEmploymentHealthCareBenefitsAbstract
1717 Cost of current service Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
1718 Interests expense Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
1719 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostNetDefinedBenefitLiabilityAsset
1720 Net pension cost (benefit) Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseInNetDefinedBenefitLiabilityAsset
1721 41913 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Funded status (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanFundedStatusDetails
1722 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1723 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1724 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1725 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1726 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1727 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1728 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1729 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1730 Funded status of the post-employment health benefits plans Abstract ggb:FundedStatusOfPostEmploymentHealthBenefitsPlansAbstract
1731 Total net liabilities Concept (Monetary) As Of Credit ifrs-full:RecognisedLiabilitiesDefinedBenefitPlan
1732 41914 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Change in obligation (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanChangeInObligationDetails
1733 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1734 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1735 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1736 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1737 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1738 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1739 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1740 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1741 Obligation at the beginning of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1742 Cost of service Concept (Monetary) For Period Credit ifrs-full:CurrentServiceCostNetDefinedBenefitLiabilityAsset
1743 Interest expense Concept (Monetary) For Period Credit ifrs-full:InterestExpenseIncomeNetDefinedBenefitLiabilityAsset
1744 Past service cost Concept (Monetary) For Period Credit ifrs-full:PastServiceCostAndGainsLossesArisingFromSettlementsNetDefinedBenefitLiabilityAsset
1745 Contributions from participants Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByPlanParticipantsNetDefinedBenefitLiabilityAsset
1746 Payment of benefits Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
1747 Gain (loss) on remeasurement Concept (Monetary) For Period Debit ifrs-full:GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAsset
1748 Exchange variations Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangesInForeignExchangeRatesNetDefinedBenefitLiabilityAsset
1749 Obligation at the end of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1750 41915 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Change in plan assets (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanChangeInPlanAssetsDetails
1751 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1752 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1753 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1754 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1755 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1756 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1757 Plan assets Member ifrs-full:PlanAssetsMember
1758 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1759 Fair value of the plan assets at the beginning of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1760 Contributions from sponsors Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByEmployerNetDefinedBenefitLiabilityAsset
1761 Contributions from participants Concept (Monetary) For Period Debit ifrs-full:ContributionsToPlanByPlanParticipantsNetDefinedBenefitLiabilityAsset
1762 Payment of benefits Concept (Monetary) For Period Debit ifrs-full:PaymentsFromPlanNetDefinedBenefitLiabilityAsset
1763 Fair value of plan assets at the end of the year Concept (Monetary) As Of Credit ifrs-full:LiabilityAssetOfDefinedBenefitPlans
1764 41916 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Gains and losses (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanGainsAndLossesDetails
1765 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1766 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1767 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1768 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1769 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1770 Equity [member] Member ifrs-full:EquityMember
1771 Pension Plan Member ifrs-full:ReserveOfRemeasurementsOfDefinedBenefitPlansMember
1772 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1773 Historical actuarial remeasurements Abstract ggb:HistoricalActuarialRemeasurementsAbstract
1774 Present value of defined benefit obligation Concept (Monetary) As Of Credit ifrs-full:DefinedBenefitObligationAtPresentValue
1775 Surplus (Deficit) Concept (Monetary) As Of Debit ifrs-full:SurplusDeficitInPlan
1776 Experience adjustments on plan liabilities Concept (Monetary) For Period Debit ggb:ActuarialGainsLossesArisingFromExperienceAdjustmentsOnDefinedBenefitLiabilities
1777 Amounts recognized as actuarial gains and losses in the statement of comprehensive income Abstract ggb:AmountsRecognizedAsActuarialGainsAndLossesInStatementOfComprehensiveIncomeAbstract
1778 Losses on actuarial obligation Concept (Monetary) For Period Credit ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans
1779 Actuarial losses recognized in Equity Concept (Monetary) For Period Debit ifrs-full:ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
1780 41917 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Assumptions (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanAssumptionsDetails
1781 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1782 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1783 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1784 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1785 Range [axis] Axis ifrs-full:RangeAxis
1786 Ranges [member] Member ifrs-full:RangesMember
1787 Minimum Member ifrs-full:BottomOfRangeMember
1788 Maximum Member ifrs-full:TopOfRangeMember
1789 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1790 Summary of assumptions used to calculate the defined benefit plans Abstract ggb:SummaryOfAssumptionsUsedToCalculateDefinedBenefitPlansAbstract
1791 Average discount rate Concept (Percent) As Of ifrs-full:ActuarialAssumptionOfDiscountRates
1792 Health treatment - rate assumed next year Concept (Percent) As Of ggb:ActuarialAssumptionOfMedicalCostTrendRatesNextYear
1793 Health treatment - Assumed rate of decline in the cost to achieve in the years of 2026 to 2041 Concept (Percent) As Of ggb:ActuarialAssumptionOfMedicalCostTrendRatesRateOfDecline
1794 41918 - Disclosure - EMPLOYEE BENEFITS - Post-employment health care benefit plan - Sensitivity Analysis (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsPostEmploymentHealthCareBenefitPlanSensitivityAnalysisDetails
1795 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1796 Defined benefit plans [axis] Axis ifrs-full:DefinedBenefitPlansAxis
1797 Defined benefit plans [member] Member ifrs-full:DefinedBenefitPlansMember
1798 Post-employment health care benefit Member ifrs-full:PostemploymentMedicalDefinedBenefitPlansMember
1799 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1800 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1801 Total service costs and interest costs Member ggb:TotalServiceCostsAndInterestCostsMember
1802 Present value of the defined benefit obligations Member ifrs-full:PresentValueOfDefinedBenefitObligationMember
1803 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
1804 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
1805 Discount rate Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
1806 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsLineItems
1807 Sensitivity analysis Abstract ifrs-full:DisclosureOfSensitivityAnalysisForActuarialAssumptionsAbstract
1808 Increase in actuarial assumption (as a percent) Concept (Percent) As Of ifrs-full:PercentageOfReasonablyPossibleIncreaseInActuarialAssumption
1809 Decrease in actuarial assumption (as a percent) Concept (Percent) As Of ifrs-full:PercentageOfReasonablyPossibleDecreaseInActuarialAssumption
1810 Increase (decrease) in defined benefit obligation due to increase in actuarial assumption Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleIncreaseInActuarialAssumption
1811 Increase (decrease) in defined benefit obligation due to decrease in actuarial assumption Concept (Monetary) As Of Credit ifrs-full:IncreaseDecreaseInDefinedBenefitObligationDueToReasonablyPossibleDecreaseInActuarialAssumption
1812 41919 - Disclosure - EMPLOYEE BENEFITS - Other retirement and termination benefits (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEmployeeBenefitsOtherRetirementAndTerminationBenefitsDetails
1813 Disclosure of net defined benefit liability (asset) [table] Table

*

*

 ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetTable
1814 Net defined benefit liability (asset) [axis] Axis ifrs-full:NetDefinedBenefitLiabilityAssetAxis
1815 Net defined benefit liability (asset) [member] Member ifrs-full:NetDefinedBenefitLiabilityAssetMember
1816 Retirement and termination benefits Member ggb:RetirementAndTerminationBenefitLiabilitiesMember
1817 EMPLOYEE BENEFITS LineItems ifrs-full:DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
1818 Total obligation Concept (Monetary) As Of Credit ifrs-full:DefinedBenefitObligationAtPresentValue
1819 42001 - Disclosure - ENVIRONMENTAL LIABILITIES (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureEnvironmentalLiabilitiesDetails
1820 Implied Table Table

*

*

 implied:Table
1821 ENVIRONMENTAL LIABILITIES Abstract ggb:DisclosureOfEnvironmentalLiabilitiesAbstract
1822 Provision for environmental liabilities Concept (Monetary) As Of Credit ifrs-full:ProvisionForDecommissioningRestorationAndRehabilitationCosts
1823 Current Concept (Monetary) As Of Credit ifrs-full:ShorttermProvisionForDecommissioningRestorationAndRehabilitationCosts
1824 Non-current Concept (Monetary) As Of Credit ifrs-full:LongtermProvisionForDecommissioningRestorationAndRehabilitationCosts
1825 42101 - Disclosure - OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureObligationsWithFidcInvestmentFundInCreditRightsDetails
1826 Implied Table Table

*

*

 implied:Table
1827 OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS Abstract ggb:ObligationsWithSecuritiesAndExchangeCommissionOfBrazilAndInvestmentFundInCreditRightsAbstract
1828 Non standardized credit right investment, fair value at inception date Concept (Monetary) For Period Debit ggb:NonStandardizedCreditRightInvestmentFundFairValueAtInceptionDate
1829 Obligations with FIDC Concept (Monetary) As Of Credit ggb:NoncurrentObligationsWithSecuritiesAndExchangeCommissionOfBrazil
1830 42201 - Disclosure - EQUITY - Common and preferred shares outstanding (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEquityCommonAndPreferredSharesOutstandingDetails
1831 Disclosure of classes of share capital [table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1832 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1833 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1834 Common shares Member ifrs-full:OrdinarySharesMember
1835 Preferred shares Member ifrs-full:PreferenceSharesMember
1836 Capital LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1837 Authorized capital Concept (Shares) As Of ifrs-full:NumberOfSharesAuthorised
1838 Shares exercise period when not a public offering Concept (xbrli:durationItemType) For Period ggb:PreferenceShareRightsExercisePeriodForOfferingThatIsNotPublic
1839 Shares exercise period for public offering Concept (xbrli:durationItemType) For Period ggb:PreferenceShareRightsExercisePeriodForPublicOffering
1840 Shares subscribed and paid up Concept (Shares) As Of ifrs-full:NumberOfSharesIssuedAndFullyPaid
1841 Total capital Concept (Monetary) As Of Credit ifrs-full:IssuedCapital
1842 Reconciliations of common and preferred outstanding shares Abstract ifrs-full:ReconciliationOfNumberOfSharesOutstandingAbstract
1843 Number of shares outstanding at beginning of the year Concept (Shares) As Of ifrs-full:NumberOfSharesOutstanding
1844 Acquisition of Treasury shares Concept (Shares) For Period ggb:PurchaseOfTreasurySharesNumber
1845 Exercise of stock options Concept (Shares) For Period ggb:IncreaseDecreaseInNumberOfSharesOutstandingThroughExerciseOfStockOptions
1846 Transfer of shares Concept (Shares) For Period ggb:IncreaseDecreaseInNumberOfSharesOutstandingThroughTreasuryShareTransactions
1847 Number of shares outstanding at end of period Concept (Shares) As Of ifrs-full:NumberOfSharesOutstanding
1848 42202 - Disclosure - EQUITY - Ownership of shares (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEquityOwnershipOfSharesDetails
1849 Disclosure of classes of share capital [table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1850 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1851 Equity [member] Member ifrs-full:EquityMember
1852 Treasury Stocks Member ifrs-full:TreasurySharesMember
1853 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1854 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1855 Common shares Member ifrs-full:OrdinarySharesMember
1856 Preferred shares Member ifrs-full:PreferenceSharesMember
1857 Categories of related parties [axis] Axis ifrs-full:CategoriesOfRelatedPartiesAxis
1858 Entity's total for related parties [member] Member ifrs-full:EntitysTotalForRelatedPartiesMember
1859 Metalurgica Gerdau S.A. Member ifrs-full:ParentMember
1860 Brazilian institutional investors Member ggb:BrazilianInstitutionalInvestorsMember
1861 Foreign institutional investors Member ggb:ForeignInstitutionalInvestorsMember
1862 Other shareholders Member ggb:OtherShareholdersMember
1863 Capital LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1864 Number of shares held Concept (Shares) As Of ifrs-full:NumberOfSharesIssued
1865 Shares Issued, Percentage Concept (Percent) As Of ggb:SharesIssuedPercentage
1866 42203 - Disclosure - EQUITY - Treasury stocks (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEquityTreasuryStocksDetails
1867 Disclosure of classes of share capital [table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1868 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1869 Equity [member] Member ifrs-full:EquityMember
1870 Treasury Stocks Member ifrs-full:TreasurySharesMember
1871 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1872 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1873 Common shares Member ifrs-full:OrdinarySharesMember
1874 Preferred shares Member ifrs-full:PreferenceSharesMember
1875 Capital LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1876 Changes in treasury stocks Concept (Text/String) For Period ggb:ChangesInTreasurySharesAbstract
1877 Number of shares outstanding at beginning of the year Concept (Shares) As Of ifrs-full:NumberOfSharesOutstanding
1878 Repurchases Concept (Shares) For Period ggb:PurchaseOfTreasurySharesNumber
1879 Exercise of stock options Concept (Shares) For Period ggb:IncreaseDecreaseInNumberOfSharesOutstandingThroughExerciseOfStockOptions
1880 Transfer of shares Concept (Shares) For Period ggb:IncreaseDecreaseInNumberOfSharesOutstandingThroughTreasuryShareTransactions
1881 Number of shares outstanding at end of period Concept (Shares) As Of ifrs-full:NumberOfSharesOutstanding
1882 Equity at beginning of period Concept (Monetary) As Of Credit ifrs-full:Equity
1883 Repurchases Concept (Monetary) For Period Debit ifrs-full:PurchaseOfTreasuryShares
1884 Exercise of stock options Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughExerciseOfOptions
1885 Transfer of shares Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTreasuryShareTransactions
1886 Equity at end of period Concept (Monetary) As Of Credit ifrs-full:Equity
1887 Average acquisition cost Concept (Share) For Period ggb:TreasurySharesAverageAcquisitionPricePerShare
1888 Investments and working capital reserve Abstract ggb:InvestmentsAndWorkingCapitalReserveAbstract
1889 Investments and working capital reserve, annual percentage Concept (Percent) For Period ggb:InvestmentsAndWorkingCapitalAnnualReservePercent
1890 42204 - Disclosure - EQUITY - Operations with non-controlling interests (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEquityOperationsWithNonControllingInterestsDetails
1891 Disclosure of classes of share capital [table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1892 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1893 Equity [member] Member ifrs-full:EquityMember
1894 Total Parent company's interest Member ifrs-full:EquityAttributableToOwnersOfParentMember
1895 Non-controlling interests Member ifrs-full:NoncontrollingInterestsMember
1896 Capital LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1897 Effects of changes in ownership interests in subsidiaries Concept (Text/String) For Period ggb:EffectsOfChangesInOwnershipInterestsInSubsidiariesAbstract
1898 Changes in the Paraopeba- Fixed Income Investment Fund Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughTransfersAndOtherChangesEquity
1899 Effect of interest changes in subsidiaries Concept (Monetary) For Period Credit ifrs-full:IncreaseDecreaseThroughChangeInEquityOfSubsidiaries
1900 42205 - Disclosure - EQUITY - Dividends and interest on capital (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEquityDividendsAndInterestOnCapitalDetails
1901 Disclosure of classes of share capital [table] Table

*

*

 ifrs-full:DisclosureOfClassesOfShareCapitalTable
1902 Components of equity [axis] Axis ifrs-full:ComponentsOfEquityAxis
1903 Equity [member] Member ifrs-full:EquityMember
1904 Retained earnings Member ifrs-full:RetainedEarningsMember
1905 Total Parent company's interest Member ifrs-full:EquityAttributableToOwnersOfParentMember
1906 Dividends and interest on capital LineItems ifrs-full:DisclosureOfClassesOfShareCapitalLineItems
1907 Minimum annual mandatory dividend (as a percent) Concept (Percent) For Period ggb:MandatoryMinimumAnnualDividendPercentage
1908 Related tax benefit arising from the recording of interest on shareholders' capital as financial expense for tax purposes Concept (Monetary) For Period Credit ggb:TaxBenefitArisingFromRecordingInterestOnShareholdersCapitalAsFinancialExpenseForTaxPurposes
1909 Appropriation of retained earnings Abstract ggb:AppropriationOfRetainedEarningsAbstract
1910 Net income (loss) available to owners of parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
1911 Constitution of legal reserve Concept (Monetary) For Period Credit ggb:LegalReserve
1912 Constitution of the tax incentives reserve Concept (Monetary) For Period Credit ggb:TaxIncentivesReserve
1913 Net income (loss) before dividends and interest on capital Concept (Monetary) For Period Credit ggb:ProfitLossBeforeDividendsAndInterestOnCapital
1914 Dividends and interest on capital Concept (Monetary) For Period Debit ggb:InterestAndDividendsPaidFromRetainedEarnings
1915 Net income (loss) before constitution of investments and working capital reserve Concept (Monetary) For Period Credit ggb:ProfitLossBeforeConstitutionOfInvestmentsAndWorkingCapital
1916 Constitution of investments and working capital reserve Concept (Monetary) For Period Debit ggb:DecreaseInEquityThroughAppropriationOfRetainedEarningsToReserves
1917 Absorption of net loss by investments and working capital reserve Concept (Monetary) For Period Credit ggb:IncreaseInEquityThroughTransferOfReservesToRetainedEarnings
1918 Dividends and interest on capital Abstract ggb:DividendsAndInterestOnCapitalAbstract
1919 Interest on capital paid (in R$/share) Concept (Share) As Of ggb:InterestOnCapitalPaidPerShare
1920 Dividends paid (in R$/share) Concept (Share) As Of ggb:DividendsPaidPerShare
1921 Outstanding shares Concept (Shares) As Of ifrs-full:NumberOfSharesOutstanding
1922 Interest Concept (Monetary) For Period Debit ggb:InterestOnShareholdersCapitalPaid
1923 Dividends Concept (Monetary) For Period Debit ifrs-full:DividendsPaid
1924 Interest and Dividends Concept (Monetary) For Period Debit ggb:InterestAndDividendsPaid
1925 Credit per share (R$) Concept (Share) For Period ifrs-full:DividendsProposedOrDeclaredBeforeFinancialStatementsAuthorisedForIssueButNotRecognisedAsDistributionToOwnersPerShare
1926 42301 - Disclosure - EARNINGS (LOSS) PER SHARE (EPS) - Basic (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEarningsLossPerShareEpsBasicDetails
1927 Earnings per share [table] Table

*

*

 ifrs-full:EarningsPerShareTable
1928 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1929 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1930 Common shares Member ifrs-full:OrdinarySharesMember
1931 Preferred shares Member ifrs-full:PreferenceSharesMember
1932 EARNINGS (LOSS) PER SHARE (EPS) LineItems ifrs-full:EarningsPerShareLineItems
1933 Basic numerator Abstract ggb:ProfitLossAttributableToOrdinaryEquityHoldersAndPreferredShareHoldersOfParentEntityBasicAbstract
1934 Net income (loss) available to owners of parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
1935 Basic denominator Abstract ggb:WeightedAverageOrdinarySharesAndPreferredSharesAndAdjustedWeightedAverageOrdinaryAndPreferredSharesBasicAbstract
1936 Weighted-average outstanding shares, after deducting the average treasury shares Concept (Shares) For Period ggb:IfrsWeightedAverageNumberOfSharesOutstandingBasic
1937 Basic earnings/(loss) per share Concept (Share) For Period ifrs-full:BasicEarningsLossPerShare
1938 42302 - Disclosure - EARNINGS (LOSS) PER SHARE (EPS) - Diluted (Details) Network

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*

 http://www.gerdau.com/role/DisclosureEarningsLossPerShareEpsDilutedDetails
1939 Earnings per share [table] Table

*

*

 ifrs-full:EarningsPerShareTable
1940 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1941 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1942 Common shares Member ifrs-full:OrdinarySharesMember
1943 Preferred shares Member ifrs-full:PreferenceSharesMember
1944 EARNINGS (LOSS) PER SHARE (EPS) LineItems ifrs-full:EarningsPerShareLineItems
1945 Diluted numerator Abstract ggb:ProfitLossAttributableToOrdinaryEquityHoldersAndPreferredShareHoldersOfParentEntityDilutedAbstract
1946 Allocated net income available to Common and Preferred shareholders Abstract ggb:NetIncomeAvailableToCommonAndPreferredShareholdersAbstract
1947 Net income (loss) available to owners of parent Concept (Monetary) For Period Credit ifrs-full:ProfitLossAttributableToOwnersOfParent
1948 Adjustment to net income in respect to the potential increase in number of shares outstanding, as a result of options granted to acquire stock of Gerdau Concept (Monetary) For Period Credit ggb:AdjustmentToProfitLossDueToDilutiveEffectOfShareOptions
1949 Net income (loss) available to owners of parent including effects of dilutive shares Concept (Monetary) For Period Credit ggb:ProfitLossAttributableToEquityHoldersOfParentEntityIncludingDilutiveEffects
1950 Diluted denominator Abstract ggb:WeightedAverageOrdinarySharesAndPreferredSharesAndAdjustedWeightedAverageOrdinaryAndPreferredSharesDilutedAbstract
1951 Weighted - average number of shares outstanding Abstract ggb:WeightedAverageNumberOfSharesCommonAndPreferredSharesOutstandingAbstract
1952 Weighted-average number of shares outstanding Concept (Shares) For Period ifrs-full:WeightedAverageShares
1953 Potential increase in number of preferred shares outstanding in respect of stock option plan Concept (Shares) For Period ggb:DilutiveEffectOfShareOptionsOnNumberOfShares
1954 Total Concept (Shares) For Period ggb:WeightedAverageNumberOfSharesOutstandingDiluted
1955 Earnings per share - Diluted (Common and Preferred Shares) Concept (Share) For Period ifrs-full:DilutedEarningsLossPerShare
1956 42401 - Disclosure - NET SALES (Details) Network

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*

 http://www.gerdau.com/role/DisclosureNetSalesDetails
1957 Implied Table Table

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*

 implied:Table
1958 NET SALES Abstract ifrs-full:RevenueAbstract
1959 Gross sales Concept (Monetary) For Period Credit ifrs-full:RevenueFromSaleOfGoods
1960 Taxes on sales Concept (Monetary) For Period Debit ggb:TaxesOnSales
1961 Discounts Concept (Monetary) For Period Debit ggb:SalesDiscounts
1962 Net sales Concept (Monetary) For Period Credit ifrs-full:Revenue
1963 42501 - Disclosure - LONG-TERM INCENTIVE PLANS - Restricted Shares and Performance Shares (Details) Network

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*

 http://www.gerdau.com/role/DisclosureLongTermIncentivePlansRestrictedSharesAndPerformanceSharesDetails
1964 Disclosure of terms and conditions of share-based payment arrangement [table] Table

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*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
1965 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
1966 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
1967 Restricted Shares and Performance Shares Member ggb:RestrictedSharesAndPerformanceSharesMember
1968 Classes of share capital [axis] Axis ifrs-full:ClassesOfShareCapitalAxis
1969 Share capital [member] Member ifrs-full:ClassesOfShareCapitalMember
1970 Preferred shares Member ifrs-full:PreferenceSharesMember
1971 LONG-TERM INCENTIVE PLANS LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
1972 Balance, beginning of year Concept (Decimal) As Of ifrs-full:NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
1973 Granted Concept (Decimal) For Period ifrs-full:NumberOfInstrumentsOtherEquityInstrumentsGranted
1974 Cancelled Concept (Decimal) For Period ifrs-full:NumberOfOtherEquityInstrumentsForfeitedInSharebasedPaymentArrangement
1975 Exercised Concept (Decimal) For Period ifrs-full:NumberOfOtherEquityInstrumentsExercisedOrVestedInSharebasedPaymentArrangement
1976 Balance, end of year Concept (Decimal) As Of ifrs-full:NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
1977 Expense from equity-settled long-term incentive plan Concept (Monetary) For Period Debit ifrs-full:ExpenseFromEquitysettledSharebasedPaymentTransactionsInWhichGoodsOrServicesReceivedDidNotQualifyForRecognitionAsAssets
1978 Treasury shares Concept (Shares) As Of ifrs-full:SharesInEntityHeldByEntityOrByItsSubsidiariesOrAssociates
1979 Grace period Concept (xbrli:durationItemType) For Period ggb:IfrsShareBasedCompensationArrangementByShareBasedPaymentAwardExpirationPeriod
1980 42502 - Disclosure - LONG-TERM INCENTIVE PLANS - Stock option activity (Details) Network

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*

 http://www.gerdau.com/role/DisclosureLongTermIncentivePlansStockOptionActivityDetails
1981 Disclosure of terms and conditions of share-based payment arrangement [table] Table

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*

 ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable
1982 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
1983 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
1984 Stock options Member ggb:IfrsEmployeeStockOptionMember
1985 LONG-TERM INCENTIVE PLANS LineItems ifrs-full:DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems
1986 Number of shares Abstract ggb:NumberOfShareOptionsAbstract
1987 Balance, beginning of year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
1988 Options Exercised Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsExercisedInSharebasedPaymentArrangement
1989 Options Forfeited Concept (Decimal) For Period ifrs-full:NumberOfShareOptionsForfeitedInSharebasedPaymentArrangement
1990 Balance, end of year Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
1991 Average exercise price in the year Abstract ggb:WeightedAverageExercisePricesOfShareOptionsAbstract
1992 Beginning of year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1993 Options Exercised Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsExercisedInSharebasedPaymentArrangement
1994 Options Forfeited Concept (Monetary) For Period ifrs-full:WeightedAverageExercisePriceOfShareOptionsForfeitedInSharebasedPaymentArrangement
1995 End of year Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
1996 Average market price of the share Concept (Monetary) For Period ifrs-full:WeightedAverageSharePrice
1997 42503 - Disclosure - LONG-TERM INCENTIVE PLANS - Exercise of stock options (Details) Network

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*

 http://www.gerdau.com/role/DisclosureLongTermIncentivePlansExerciseOfStockOptionsDetails
1998 Disclosure of range of exercise prices of outstanding share options [table] Table

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*

 ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsTable
1999 Types of share-based payment arrangements [axis] Axis ifrs-full:TypesOfSharebasedPaymentArrangementsAxis
2000 Share-based payment arrangements [member] Member ifrs-full:SharebasedPaymentArrangementsMember
2001 Stock options Member ggb:IfrsEmployeeStockOptionMember
2002 Ranges of exercise prices for outstanding share options [axis] Axis ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsAxis
2003 Ranges of exercise prices for outstanding share options [member] Member ifrs-full:RangesOfExercisePricesForOutstandingShareOptionsMember
2004 R$ 16.86 Member ggb:ExercisePriceRangeOneMember
2005 R$ 18.58 Member ggb:ExercisePriceRangeTwoMember
2006 Exercise price of options LineItems ifrs-full:DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsLineItems
2007 Exercise price Concept (Monetary) As Of ifrs-full:ExercisePriceOfOutstandingShareOptions
2008 Quantity (in shares) Concept (Decimal) As Of ifrs-full:NumberOfOutstandingShareOptions
2009 Average period of grace (in years) Concept (Decimal) As Of ifrs-full:WeightedAverageRemainingContractualLifeOfOutstandingShareOptions
2010 Average exercise price Concept (Monetary) As Of ifrs-full:WeightedAverageExercisePriceOfShareOptionsOutstandingInSharebasedPaymentArrangement
2011 Number exercisable at end of the period (in shares) Concept (Decimal) As Of ifrs-full:NumberOfShareOptionsExercisableInSharebasedPaymentArrangement
2012 42601 - Disclosure - SEGMENT REPORTING - Summary (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureSegmentReportingSummaryDetails
2013 Disclosure of operating segments [table] Table

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*

 ifrs-full:DisclosureOfOperatingSegmentsTable
2014 Segment consolidation items [axis] Axis ifrs-full:SegmentConsolidationItemsAxis
2015 Entity's total for segment consolidation items [member] Member ifrs-full:EntitysTotalForSegmentConsolidationItemsMember
2016 Operating Segments Member ifrs-full:OperatingSegmentsMember
2017 Eliminations and Adjustments Member ifrs-full:MaterialReconcilingItemsMember
2018 Segments [axis] Axis ifrs-full:SegmentsAxis
2019 Segments [member] Member ifrs-full:SegmentsMember
2020 Brazil Member ggb:BrazilSegmentMember
2021 North America Member ggb:NorthAmericaSegmentMember
2022 South America Member ggb:SouthAmericaSegmentMember
2023 Special Steel Member ggb:SpecialSteelSegmentMember
2024 Segment reporting as per business segments LineItems ifrs-full:DisclosureOfOperatingSegmentsLineItems
2025 Net sales Concept (Monetary) For Period Credit ifrs-full:Revenue
2026 Cost of sales Concept (Monetary) For Period Debit ifrs-full:CostOfSales
2027 GROSS PROFIT Concept (Monetary) For Period Credit ifrs-full:GrossProfit
2028 Selling, general and administrative expenses Concept (Monetary) For Period Debit ifrs-full:SellingGeneralAndAdministrativeExpense
2029 Other operating income (expenses) Concept (Monetary) For Period Credit ifrs-full:OtherOperatingIncomeExpense
2030 Impairment of assets Concept (Monetary) For Period Debit ggb:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipmentAndGoodwill
2031 Results in operations with subsidiaries and associate company Concept (Monetary) For Period Credit ggb:GainsLossesOnAssetsHeldForSaleAndSalesOfInterestInSubsidiariesAndAssociates
2032 Reversal of provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalNet
2033 Equity in earnings of unconsolidated companies Concept (Monetary) For Period Credit ggb:ShareOfProfitLossOfInvestmentsAccountedForUsingEquityMethod
2034 INCOME (LOSS) BEFORE FINANCIAL INCOME (EXPENSES) AND TAXES Concept (Monetary) For Period Credit ifrs-full:ProfitLossFromOperatingActivities
2035 Financial result, net Concept (Monetary) For Period Credit ifrs-full:FinanceIncomeCost
2036 INCOME (LOSS) BEFORE TAXES Concept (Monetary) For Period Credit ifrs-full:ProfitLossBeforeTax
2037 Income and social contribution taxes Concept (Monetary) For Period Debit ifrs-full:IncomeTaxExpenseContinuingOperations
2038 Net income (loss) Concept (Monetary) For Period Credit ifrs-full:ProfitLoss
2039 Depreciation/amortization Concept (Monetary) For Period Debit ifrs-full:DepreciationAndAmortisationExpense
2040 Investments in associates and jointly-controlled entities Concept (Monetary) As Of Debit ifrs-full:InvestmentAccountedForUsingEquityMethod
2041 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
2042 Total liabilities Concept (Monetary) As Of Credit ifrs-full:Liabilities
2043 42602 - Disclosure - SEGMENT REPORTING - Revenues by Geographical Region (Details) Network

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*

 http://www.gerdau.com/role/DisclosureSegmentReportingRevenuesByGeographicalRegionDetails
2044 Disclosure of geographical areas [table] Table

*

*

 ifrs-full:DisclosureOfGeographicalAreasTable
2045 Geographical areas [axis] Axis ifrs-full:GeographicalAreasAxis
2046 Geographical areas [member] Member ifrs-full:GeographicalAreasMember
2047 Brazil Member country:BR
2048 Latin America Member ggb:LatinAmericanCountriesExcludingBrazilMember
2049 North America Member ggb:NorthAmericanCountriesExcludingMexicoMember
2050 Europe/Asia Member ggb:EuropeAndAsiaMember
2051 Segment reporting as per geographical areas LineItems ifrs-full:DisclosureOfGeographicalAreasLineItems
2052 Net sales Concept (Monetary) For Period Credit ifrs-full:Revenue
2053 Total assets Concept (Monetary) As Of Debit ifrs-full:Assets
2054 42701 - Disclosure - INSURANCE (Details) Network

*

*

 http://www.gerdau.com/role/DisclosureInsuranceDetails
2055 Disclosure of types of insurance contracts [table] Table

*

*

 ifrs-full:DisclosureOfTypesOfInsuranceContractsTable
2056 Types of insurance contracts [axis] Axis ifrs-full:TypesOfInsuranceContractsAxis
2057 Insurance contracts [member] Member ifrs-full:InsuranceContractsMember
2058 Equity Member ggb:EquityInsuranceContractsMember
2059 Business Interruption Member ggb:BusinessInterruptionInsuranceContractsMember
2060 Civil Liability Member ggb:CivilLiabilityInsuranceContractsMember
2061 INSURANCE LineItems ifrs-full:DisclosureOfTypesOfInsuranceContractsLineItems
2062 Amount of assets or liabilities covered under insurance contracts Concept (Monetary) As Of Debit ggb:AssetsLiabilitiesCoveredUnderInsuranceContracts
2063 42801 - Disclosure - IMPAIRMENT OF ASSETS (Details) Network

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*

 http://www.gerdau.com/role/DisclosureImpairmentOfAssetsDetails
2064 Disclosure of impairment loss and reversal of impairment loss [table] Table

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*

 ifrs-full:DisclosureOfImpairmentLossAndReversalOfImpairmentLossTable
2065 Segments [axis] Axis ifrs-full:SegmentsAxis
2066 Segments [member] Member ifrs-full:SegmentsMember
2067 North America Member ggb:NorthAmericaSegmentMember
2068 South America Member ggb:SouthAmericaSegmentMember
2069 Brazil Member ggb:BrazilSegmentMember
2070 Special Steel Member ggb:SpecialSteelSegmentMember
2071 Actuarial assumptions [axis] Axis ifrs-full:ActuarialAssumptionsAxis
2072 Actuarial assumptions [member] Member ifrs-full:ActuarialAssumptionsMember
2073 Discount rate Member ifrs-full:ActuarialAssumptionOfDiscountRatesMember
2074 Perpetuity growth rate Member ggb:PerpetuityGrowthRateMember
2075 Impairment of assets LineItems ifrs-full:DisclosureOfImpairmentLossAndReversalOfImpairmentLossLineItems
2076 Total impairment of non-financial assets Concept (Monetary) For Period Debit ggb:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipmentAndGoodwill
2077 Impairment of property, plant and equipment Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
2078 Impairment of goodwill Concept (Monetary) For Period ifrs-full:ImpairmentLossRecognisedInProfitOrLossGoodwill
2079 Number of operating segments Concept (Integer) For Period ggb:IfrsNumberOfOperatingSegments
2080 Period for projecting the cash flows for the goodwill impairment test Concept (Text/String) For Period ifrs-full:ExplanationOfPeriodOverWhichManagementHasProjectedCashFlows
2081 Perpetuity growth rate Concept (Percent) As Of ifrs-full:DescriptionOfGrowthRateUsedToExtrapolateCashFlowProjections
2082 Pre-tax discount rate Concept (Percent) As Of ifrs-full:DescriptionOfDiscountRatesAppliedToCashFlowProjections
2083 Amount by which unit's recoverable amount is (below) exceeds its carrying value Concept (Monetary) As Of Debit ggb:AmountByWhichUnitSRecoverableAmountIsBelowOrExceedsItsCarryingAmount
2084 Sensitivity analysis, percent of increase Concept (Percent) As Of ggb:SensitivityAnalysisPercentageAppreciation
2085 Sensitivity analysis, percent of decrease Concept (Percent) As Of ggb:SensitivityAnalysisPercentageDepreciation
2086 Sensitivity analysis, amount above (below) book value Concept (Monetary) As Of Debit ggb:SensitivityAnalysisAmountAboveBelowBookValueAttributableToChangeInRateUsedToEstimatePresentValue
2087 42901 - Disclosure - EXPENSES BY NATURE - Classified by nature (Details) Network

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*

 http://www.gerdau.com/role/DisclosureExpensesByNatureClassifiedByNatureDetails
2088 Implied Table Table

*

*

 implied:Table
2089 EXPENSES BY NATURE Abstract ifrs-full:ExpenseByNatureAbstract
2090 Depreciation and amortisation Concept (Monetary) For Period Debit ifrs-full:DepreciationAndAmortisationExpense
2091 Labor expenses Concept (Monetary) For Period Debit ifrs-full:EmployeeBenefitsExpense
2092 Raw material and consumption material Concept (Monetary) For Period Debit ifrs-full:RawMaterialsAndConsumablesUsed
2093 Freight Concept (Monetary) For Period Debit ggb:FreightExpense
2094 Impairment of assets Concept (Monetary) For Period Debit ggb:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipmentAndGoodwill
2095 Gains and losses on assets held for sale and sales of interest in subsidiaries Concept (Monetary) For Period Credit ggb:GainsLossesOnAssetsHeldForSaleAndSalesOfInterestInSubsidiariesAndAssociates
2096 Reversal of provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalNet
2097 Other expenses/income, net Concept (Monetary) For Period Debit ifrs-full:OtherExpenseByNature
2098 Total Expenses Concept (Monetary) For Period Debit ifrs-full:ExpenseByNature
2099 42902 - Disclosure - EXPENSES BY NATURE - Classified by function (Details) Network

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 http://www.gerdau.com/role/DisclosureExpensesByNatureClassifiedByFunctionDetails
2100 Implied Table Table

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 implied:Table
2101 EXPENSES BY NATURE Abstract ifrs-full:ExpenseByNatureAbstract
2102 Cost of sales Concept (Monetary) For Period Debit ifrs-full:CostOfSales
2103 Selling expenses Concept (Monetary) For Period Debit ifrs-full:SellingExpense
2104 Allowance for doubtful accounts Concept (Monetary) For Period Debit ifrs-full:ImpairmentLossRecognisedInProfitOrLossTradeReceivables
2105 General and administrative expenses Concept (Monetary) For Period Debit ifrs-full:GeneralAndAdministrativeExpense
2106 Other operating income Concept (Monetary) For Period Credit ifrs-full:OtherIncome
2107 Other operating expenses Concept (Monetary) For Period Debit ifrs-full:OtherExpenseByFunction
2108 Impairment of assets Concept (Monetary) For Period Debit ggb:ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipmentAndGoodwill
2109 Gains and losses on assets held for sale and sales of interest in subsidiaries Concept (Monetary) For Period Credit ggb:GainsLossesOnAssetsHeldForSaleAndSalesOfInterestInSubsidiariesAndAssociates
2110 Reversal of provision for tax liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalNet
2111 Total Expenses Concept (Monetary) For Period Debit ifrs-full:ExpenseByNature
2112 43001 - Disclosure - FINANCIAL INCOME (Details) Network

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 http://www.gerdau.com/role/DisclosureFinancialIncomeDetails
2113 Implied Table Table

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 implied:Table
2114 FINANCIAL INCOME Abstract ggb:FinancialIncomeAbstract
2115 Income from short-term investments Concept (Monetary) For Period Credit ifrs-full:InterestIncomeOnFinancialAssetsHeldForTrading
2116 Interest income and other financial income Concept (Monetary) For Period Credit ggb:InterestIncomeAndOtherFinancialIncome
2117 Financial Income Concept (Monetary) For Period Credit ifrs-full:FinanceIncome
2118 Interest on debt Concept (Monetary) For Period Debit ifrs-full:InterestExpenseOnBorrowings
2119 Monetary variation and other financial expenses Concept (Monetary) For Period Debit ggb:MonetaryVariationAndOtherFinancialExpenses
2120 Financial expenses Concept (Monetary) For Period Debit ifrs-full:FinanceCosts
2121 Bonds repurchases Concept (Monetary) For Period Debit ggb:RepurchaseOfBonds
2122 Exchange Variation, net Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
2123 Reversal of monetary update of contingent liabilities, net Concept (Monetary) For Period Credit ggb:ContingentLiabilitiesGainOnReversalOfMonetaryUpdateNet
2124 Gains and losses on financial instruments, net Concept (Monetary) For Period Credit ifrs-full:GainsLossesOnChangeInFairValueOfDerivatives
2125 Financial result, net Concept (Monetary) For Period Credit ifrs-full:FinanceIncomeCost

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