cm:Concept: us-gaap:DiscontinuedOperationEquityMethodInvestmentRetainedAfterDisposalOwnershipInterestPriorToDisposal
| Discontinued Operation, Equity Method Investment Retained after Disposal, Ownership Interest Prior to Disposal |
| us-gaap:DiscontinuedOperationEquityMethodInvestmentRetainedAfterDisposalOwnershipInterestPriorToDisposal |
| Percent, prior to disposal, of ownership interest of a discontinued operation in which an equity method investment is retained. |
| cm:Concept |
| Percent (num:percentItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DiscontinuedOperationEquityMethodInvestmentRetainedAfterDisposalOwnershipInterestPriorToDisposal |