cm:Concept: us-gaap:AssetsDesignatedToClosedBlockFixedMaturityAvailableForSaleAtFairValue
| Assets Designated to Closed Block, Fixed Maturity, Available-for-sale, at Fair Value |
| us-gaap:AssetsDesignatedToClosedBlockFixedMaturityAvailableForSaleAtFairValue |
| Fair value of investments in debt securities that are deemed to be available for sale that are allocated to the segregated group of participating or dividend-paying policies and contracts identified as the closed block. Change in fair of such securities is 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) |
| Debit |
| false |
| us-gaap:AssetsDesignatedToClosedBlockFixedMaturityAvailableForSaleAtFairValue |