cm:Concept: us-gaap:LiabilityForAsbestosAndEnvironmentalClaimsDescription
| Liability for Asbestos and Environmental Claims, Description |
| us-gaap:LiabilityForAsbestosAndEnvironmentalClaimsDescription |
| Describes estimated costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental (remediation) claims. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LiabilityForAsbestosAndEnvironmentalClaimsDescription |