cm:Level3TextBlock: us-gaap:ScheduleOfShareBasedCompensationNonemployeeDirectorStockAwardPlanActivityTableTextBlock
| Share-based Payment Arrangement, Nonemployee Director Award Plan, Activity [Table Text Block] |
| us-gaap:ScheduleOfShareBasedCompensationNonemployeeDirectorStockAwardPlanActivityTableTextBlock |
| Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for stock awards granted to nonemployee directors that were outstanding at the beginning and end of the year, and the number of awards 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:ScheduleOfShareBasedCompensationNonemployeeDirectorStockAwardPlanActivityTableTextBlock |
| SharebasedCompensationNonemployeeDirectorStockAwardPlanActivity |