cm:Concept: us-gaap:DescriptionOfNetInvestmentHedgeEffectOnEarningsAndComprehensiveIncome
| Description of Net Investment Hedge Effect on Earnings and Comprehensive Income |
| us-gaap:DescriptionOfNetInvestmentHedgeEffectOnEarningsAndComprehensiveIncome |
| Description of the effects of hedges of net investments in foreign operations. Includes description of effects on earnings and comprehensive income. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfNetInvestmentHedgeEffectOnEarningsAndComprehensiveIncome |