cm:Concept: us-gaap:ClosedBlockOperationsPolicyholderBenefits
| Closed Block Operations, Policyholder Benefits |
| us-gaap:ClosedBlockOperationsPolicyholderBenefits |
| An expense for the period for estimated policy claims in an insurance entity's segregated group of participating or dividend-paying policies and contracts along with the assets allocated to them (known as a closed block), as typically reported in a table of closed block operations as part of summarized financial data. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ClosedBlockOperationsPolicyholderBenefits |