cm:Level2TextBlock: us-gaap:LongDurationContractsRevenueRecognitionPolicy
| Long-Duration Contracts Revenue Recognition, Policy [Policy Text Block] |
| us-gaap:LongDurationContractsRevenueRecognitionPolicy |
| Disclosure of accounting policy for revenue recognition for long-duration contracts, including the timing of revenue recognition and the basis for determining the amount of revenue recognized, excluding fees earned on separate accounts. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LongDurationContractsRevenueRecognitionPolicy |