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