cm:Concept: us-gaap:ExcessOfReportedClosedBlockLiabilitiesOverAssetsDesignatedToClosedBlock
| Excess of Reported Closed Block Liabilities over Assets Designated to Closed Block |
| us-gaap:ExcessOfReportedClosedBlockLiabilitiesOverAssetsDesignatedToClosedBlock |
| The difference between the liabilities of and the assets allocated to the segregated group of participating or dividend-paying policies and contracts identified as the closed block. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:ExcessOfReportedClosedBlockLiabilitiesOverAssetsDesignatedToClosedBlock |