cm:Concept: us-gaap:AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits
| Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units |
| us-gaap:AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits |
| Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of stock options or restrictive stock units (RSUs). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits |