cm:Concept: us-gaap:ClosedBlockInvestmentsAvailableForSaleChangeInUnrealizedAppreciation
| Closed Block Investments, Available-for-sale, Change in Unrealized Appreciation |
| us-gaap:ClosedBlockInvestmentsAvailableForSaleChangeInUnrealizedAppreciation |
| The net increase or decrease in the period in the fair value of the fixed maturity and equity investments designated as available for sale as of the balance sheet date that were allocated to the segregated group of participating or dividend-paying policies and contracts identified as a closed block. Also a component of change in other comprehensive income in the period, which is reflected in the closed block disclosure. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:ClosedBlockInvestmentsAvailableForSaleChangeInUnrealizedAppreciation |