cm:Concept: us-gaap:UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities
| Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities |
| us-gaap:UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities |
| Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities |