cm:Concept: us-gaap:MarketRiskBenefitAfterIncreaseDecreaseFromInstrumentSpecificCreditRisk
| Market Risk Benefit, after Increase (Decrease) from Instrument-Specific Credit Risk |
| us-gaap:MarketRiskBenefitAfterIncreaseDecreaseFromInstrumentSpecificCreditRisk |
| Amount, before effect of reinsurance and after accumulated increase (decrease) in instrument-specific credit risk, 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:MarketRiskBenefitAfterIncreaseDecreaseFromInstrumentSpecificCreditRisk |