cm:Concept: us-gaap:NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic
| Net Income (Loss) from Discontinued Operations Available to Common Shareholders, Basic |
| us-gaap:NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic |
| Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) from discontinued operations available to common shareholders. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic |