cm:Concept: us-gaap:PresentValueOfFutureInsuranceProfitExperienceAdjustment
| Present Value of Future Insurance Profit, Experience Adjustment |
| us-gaap:PresentValueOfFutureInsuranceProfitExperienceAdjustment |
| Amount of expense for writeoff from unexpected insurance contract termination, charged against previously capitalized present value of future profit of insurance contract acquired in business combination. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:PresentValueOfFutureInsuranceProfitExperienceAdjustment |