cm:Concept: us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease
| Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease) |
| us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease |
| Amount of increase (decrease) in the cumulative translation adjustment from gain (loss), after tax, 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) |
| (no balance type) |
| false |
| us-gaap:TranslationAdjustmentForNetInvestmentHedgeNetOfTaxPeriodIncreaseDecrease |