cm:Concept: us-gaap:UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesDiluted
| Undistributed Continuing Operation Earnings (Loss), Allocation to Participating Securities, Diluted |
| us-gaap:UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesDiluted |
| Amount of undistributed earnings (loss) from continuing operations allocated to participating securities for diluted earnings (loss) per share or per unit calculation under two-class method. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesDiluted |