cm:Level2TextBlock: us-gaap:ShortDurationContractsRevenueRecognitionPolicy
| Short-Duration Contracts Revenue Recognition, Policy [Policy Text Block] |
| us-gaap:ShortDurationContractsRevenueRecognitionPolicy |
| Disclosure of accounting policy for revenue recognition on short-duration contracts, the timing of revenue recognition, and the bases for determining the amount of revenue recognized. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ShortDurationContractsRevenueRecognitionPolicy |