cm:Concept: us-gaap:DescriptionOfLocationOfGainLossOnNetInvestmentHedgesInFinancialStatements
| Description of Location of Gain (Loss) on Net Investment Hedges in Financial Statements |
| us-gaap:DescriptionOfLocationOfGainLossOnNetInvestmentHedgesInFinancialStatements |
| Description of where the net gain (loss) on hedges of net investments in foreign operations is reported in the entity's financial statements. Includes description for amounts included in other comprehensive income. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfLocationOfGainLossOnNetInvestmentHedgesInFinancialStatements |