cm:Concept: us-gaap:ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries
| Proceeds from Divestiture of Interest in Consolidated Subsidiaries |
| us-gaap:ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries |
| The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or the sale of investment in consolidated subsidiaries (generally greater than 50 percent). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries |