cm:Concept: us-gaap:AdditionalLiabilityLongDurationInsuranceRemeasurementGainLoss
| Additional Liability, Long-Duration Insurance, Remeasurement Gain (Loss) |
| us-gaap:AdditionalLiabilityLongDurationInsuranceRemeasurementGainLoss |
| Amount of remeasurement gain (loss) on present value of total expected payment to policyholder in excess of present value of total expected assessment from application of revised benefit ratio as of contract issue date. 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:AdditionalLiabilityLongDurationInsuranceRemeasurementGainLoss |