cm:Concept: us-gaap:ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseDescriptionOfChangeInAssumptions
| Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Description of Change in Assumptions |
| us-gaap:ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseDescriptionOfChangeInAssumptions |
| Description of changes in assumptions made in calculating the liability for unpaid claims and claim adjustment expense for short-duration insurance contracts. Includes, but is not limited to, the reasons for the change and the effects on the financial statements. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseDescriptionOfChangeInAssumptions |