cm:Concept: us-gaap:MarketRiskBenefitNetAmountAtRisk
| Market Risk Benefit, Net Amount at Risk |
| us-gaap:MarketRiskBenefitNetAmountAtRisk |
| Amount of guaranteed benefit in excess of current account balance of 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:MarketRiskBenefitNetAmountAtRisk |