cm:Concept: us-gaap:AdditionalLiabilityLongDurationInsuranceIncreaseDecreaseFromDiscountRateChange
| Additional Liability, Long-Duration Insurance, Increase (Decrease) from Discount Rate Change |
| us-gaap:AdditionalLiabilityLongDurationInsuranceIncreaseDecreaseFromDiscountRateChange |
| Amount of increase (decrease) in present value of total expected payment to policyholder in excess of present value of total expected assessment from cash flow assumption change for future cash flows from change in discount rate. Excludes benefit classified as market risk benefit or under provisions of Topic 815 on derivative and hedging. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:AdditionalLiabilityLongDurationInsuranceIncreaseDecreaseFromDiscountRateChange |