cm:Concept: us-gaap:IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve
| Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve |
| us-gaap:IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve |
| Amount of increase (decrease) in liability to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve |