cm:Table: us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValueTable
| Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table] |
| us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValueTable |
| Disclosure of information about investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. |
| cm:Table |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPositionFairValueTable |