cm:Concept: us-gaap:BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestSignificantInputs
| Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Significant Inputs |
| us-gaap:BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestSignificantInputs |
| This item represents the significant inputs, including any assumptions, used by management to estimate the fair value of the noncontrolling interest in the acquiree at the acquisition date. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestSignificantInputs |