cm:Level2TextBlock: us-gaap:LoansAndLeasesReceivableMortgageBankingActivitiesPolicy
| Mortgage Banking Activity [Policy Text Block] |
| us-gaap:LoansAndLeasesReceivableMortgageBankingActivitiesPolicy |
| Disclosure of accounting policy for the lending, securitization, sales, transfers and servicing practices for mortgage banking activities. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LoansAndLeasesReceivableMortgageBankingActivitiesPolicy |