cm:Concept: us-gaap:ForeignReinsuranceTransactionsClaimsRecognizedAsIncome
| Foreign Reinsurance Transactions, Claims Recognized as Income |
| us-gaap:ForeignReinsuranceTransactionsClaimsRecognizedAsIncome |
| Amounts for insured risks on policies that have been ceded to entities outside the United States and for which claims income is paid or due and owing to the ceding entity. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:ForeignReinsuranceTransactionsClaimsRecognizedAsIncome |