cm:Concept: us-gaap:ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet
| Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net |
| us-gaap:ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet |
| Undiscounted amount, after reinsurance, of incurred-but-not-reported (IBNR) liabilities plus expected development on reported claims, for claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet |