cm:Level3TextBlock: us-gaap:ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVestTableTextBlock
| Share-based Compensation Arrangements by Share-based Payment Award, Performance-Based Units, Vested and Expected to Vest [Table Text Block] |
| us-gaap:ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVestTableTextBlock |
| Tabular disclosure of number, weighted-average exercise price or conversion ratio, aggregate intrinsic value, and weighted-average remaining contractual term for outstanding performance-based awards that are fully vested and expected to vest. Includes, but is not limited to, unvested awards for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur. |
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| us-gaap:ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVestTableTextBlock |
| SharebasedCompensationArrangementBySharebasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVest |