cm:Concept: us-gaap:OciMarketRiskBenefitInstrumentSpecificCreditRiskGainLossReclassificationAdjustmentFromAociAfterTax
| OCI, Market Risk Benefit, Instrument-Specific Credit Risk, Gain (Loss), Reclassification Adjustment from AOCI, after Tax |
| us-gaap:OciMarketRiskBenefitInstrumentSpecificCreditRiskGainLossReclassificationAdjustmentFromAociAfterTax |
| Amount, after tax, of reclassification 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, realized in income upon derecognition for benefit. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:OciMarketRiskBenefitInstrumentSpecificCreditRiskGainLossReclassificationAdjustmentFromAociAfterTax |