cm:Level3TextBlock: us-gaap:ScheduleOfShareBasedCompensationStockOptionsAndStockAppreciationRightsAwardActivityTableTextBlock
| Share-based Payment Arrangement, Option and Stock Appreciation Rights, Activity [Table Text Block] |
| us-gaap:ScheduleOfShareBasedCompensationStockOptionsAndStockAppreciationRightsAwardActivityTableTextBlock |
| Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for stock options and stock appreciation rights that were outstanding at the beginning and end of the year, exercisable at the end of the year, and the number of stock options and stock appreciation rights that were granted, exercised or converted, forfeited, and expired during the year. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfShareBasedCompensationStockOptionsAndStockAppreciationRightsAwardActivityTableTextBlock |
| SharebasedCompensationStockOptionsAndStockAppreciationRightsAwardActivity |