cm:Concept: us-gaap:LiabilityForFuturePolicyBenefitExpectedNetPremiumOriginalDiscountRateBeforeCashFlowAndReinsurance
| Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance |
| us-gaap:LiabilityForFuturePolicyBenefitExpectedNetPremiumOriginalDiscountRateBeforeCashFlowAndReinsurance |
| Amount, before effect of reinsurance and current period update of cash flow assumption, of expected net premium component of liability for future policy benefit, discounted at original rate. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:LiabilityForFuturePolicyBenefitExpectedNetPremiumOriginalDiscountRateBeforeCashFlowAndReinsurance |