cm:Concept: us-gaap:ForeignReinsuranceUnderOpenYearMethodComment
| Foreign Reinsurance under Open Year Method Comment |
| us-gaap:ForeignReinsuranceUnderOpenYearMethodComment |
| Methodology and assumptions regarding insurance assumed by insurance entities outside the United States for which the open year method of accounting for these contracts is being used (premiums are included in the underwriting account when they become reasonably determinable). |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ForeignReinsuranceUnderOpenYearMethodComment |