cm:Axis: us-gaap:ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis
| Credit Deterioration Surveillance Category [Axis] |
| us-gaap:ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis |
| Information by category used by management to monitor and track credit deterioration of an insured party's obligations on the underlying contracts (such as debt agreements). |
| cm:Axis |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis |