cm:Concept: us-gaap:DerivativesUsedInNetInvestmentHedgeTaxExpenseBenefit
| Derivatives used in Net Investment Hedge, Tax Expense (Benefit) |
| us-gaap:DerivativesUsedInNetInvestmentHedgeTaxExpenseBenefit |
| Amount of income tax expense (benefit) from transactions on foreign currency derivatives that are designated as, and are effective as, economic hedges of a net investment in a foreign entity. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:DerivativesUsedInNetInvestmentHedgeTaxExpenseBenefit |