cm:Member: us-gaap:OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain
| Other than Temporary Impairment, Credit Losses Recognized in Earnings, Categories of Investments [Domain] |
| us-gaap:OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain |
| Provides the categories of debt securities, available-for-sale or held-to-maturity, on which an entity may recognize other than temporary impairments (OTTI) for which a portion related to credit losses has been recognized in earnings and a portion related to all other factors has been recognized in other comprehensive income. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain |