cm:Concept: us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1
| Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year |
| us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1 |
| Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1 |