cm:Member: us-gaap:AociLiabilityForFuturePolicyBenefitIncludingNoncontrollingInterestMember
| AOCI, Liability for Future Policy Benefit, Including Noncontrolling Interest [Member] |
| us-gaap:AociLiabilityForFuturePolicyBenefitIncludingNoncontrollingInterestMember |
| Accumulated other comprehensive income (loss) (AOCI) from (increase) decrease in liability for future policy benefit from change in discount rate, including portion attributable to noncontrolling interest. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:AociLiabilityForFuturePolicyBenefitIncludingNoncontrollingInterestMember |