cm:Level3TextBlock: us-gaap:ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock
| Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] |
| us-gaap:ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock |
| Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
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| us-gaap:ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock |
| SharebasedPaymentAwardStockOptionsValuationAssumptions |