cm:Concept: us-gaap:ClosedBlockOperationsNetInvestmentIncome
| Closed Block Operations, Net Investment Income |
| us-gaap:ClosedBlockOperationsNetInvestmentIncome |
| Income for the period from the investments allocated to an insurance entity's segregated group of participating or dividend-paying policies and contracts (known as a closed block), net of investment expenses, which are typically reported in a table of closed block operations. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:ClosedBlockOperationsNetInvestmentIncome |