cm:Concept: us-gaap:PresentValueOfFutureInsuranceProfitsUnrealizedInvestmentLosses1
| Present Value of Future Insurance Profits, Unrealized Investment Loss |
| us-gaap:PresentValueOfFutureInsuranceProfitsUnrealizedInvestmentLosses1 |
| Amount of unrealized investment loss which increases present value of future profits of insurance contract acquired in business combination. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:PresentValueOfFutureInsuranceProfitsUnrealizedInvestmentLosses1 |