cm:Concept: us-gaap:UnrecognizedTaxBenefitsDecreasesResultingFromCurrentPeriodTaxPositions
| Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions |
| us-gaap:UnrecognizedTaxBenefitsDecreasesResultingFromCurrentPeriodTaxPositions |
| Amount of decrease in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:UnrecognizedTaxBenefitsDecreasesResultingFromCurrentPeriodTaxPositions |