cm:Concept: us-gaap:LiabilitiesForGuaranteesOnLongDurationContractsOtherLiabilityAdjustments
| Liabilities for Guarantees on Long-Duration Contracts, Other Liability Adjustments |
| us-gaap:LiabilitiesForGuaranteesOnLongDurationContractsOtherLiabilityAdjustments |
| Net amount of other increases or decreases to the liability for guaranteed minimum benefits on long-duration contracts occurring during the period. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:LiabilitiesForGuaranteesOnLongDurationContractsOtherLiabilityAdjustments |