cm:Concept: us-gaap:LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitIncreaseDecreaseForOtherChange
| Liability for Future Policy Benefit, Expected Future Policy Benefit, Increase (Decrease) for Other Change |
| us-gaap:LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitIncreaseDecreaseForOtherChange |
| Amount of increase (decrease) in expected future policy benefit and expense component for liability for future policy benefit from change, classified as other. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitIncreaseDecreaseForOtherChange |