cm:Concept: us-gaap:OciMarketRiskBenefitInstrumentSpecificCreditRiskAdjustmentFromAociForDerecognitionBeforeTax
| OCI, Market Risk Benefit, Instrument-Specific Credit Risk, Adjustment from AOCI for Derecognition, before Tax |
| us-gaap:OciMarketRiskBenefitInstrumentSpecificCreditRiskAdjustmentFromAociForDerecognitionBeforeTax |
| Amount, before tax, of adjustment from accumulated other comprehensive income for gain (loss) (AOCI) from (increase) decrease in instrument-specific credit risk on 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, not recognized in income and used in calculating liability for future policy benefit for payout annuity. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:OciMarketRiskBenefitInstrumentSpecificCreditRiskAdjustmentFromAociForDerecognitionBeforeTax |