cm:Concept: us-gaap:DeferredPolicyAcquisitionCostForeignCurrencyTranslationAdjustmentAndOther
| Deferred Policy Acquisition Cost, Foreign Currency Translation Adjustment and Other |
| us-gaap:DeferredPolicyAcquisitionCostForeignCurrencyTranslationAdjustmentAndOther |
| Amount of increase (decrease) in deferred policy acquisition cost due to the effect of foreign currency translation gain (loss) and increase (decrease) classified as other. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:DeferredPolicyAcquisitionCostForeignCurrencyTranslationAdjustmentAndOther |