cm:Concept: us-gaap:AssetsDesignatedToClosedBlockEquitySecuritiesAvailableForSaleAtFairValue
| Assets Designated to Closed Block, Equity Securities, Available-for-sale, at Fair Value |
| us-gaap:AssetsDesignatedToClosedBlockEquitySecuritiesAvailableForSaleAtFairValue |
| Fair value of equity securities designated as available for sale, which are allocated to the segregated group of participating or dividend-paying policies and contracts identified as the 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) |
| Debit |
| false |
| us-gaap:AssetsDesignatedToClosedBlockEquitySecuritiesAvailableForSaleAtFairValue |