cm:Concept: us-gaap:MarketRiskBenefitLiabilityAmount
| Market Risk Benefit, Liability, Amount |
| us-gaap:MarketRiskBenefitLiabilityAmount |
| Amount of liability position for contract or contract feature in long-duration contract issued by insurance entity that both protects contract holder from other-than-nominal capital market risk and exposes insurance entity to other-than-nominal capital market risk. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:MarketRiskBenefitLiabilityAmount |