cm:Concept: us-gaap:TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseGrossOfTax
| Derivatives used in Net Investment Hedge, Increase (Decrease), Gross of Tax |
| us-gaap:TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseGrossOfTax |
| Amount, before tax, of increase (decrease) in the cumulative translation adjustment from gain (loss) 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) |
| Credit |
| false |
| us-gaap:TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseGrossOfTax |