cm:Level2TextBlock: us-gaap:LoansAndLeasesReceivableRealEstateAcquiredThroughForeclosurePolicy
| Financing Receivable, Real Estate Acquired Through Foreclosure [Policy Text Block] |
| us-gaap:LoansAndLeasesReceivableRealEstateAcquiredThroughForeclosurePolicy |
| Disclosure of accounting policy for real estate acquired through foreclosure. |
| cm:Level2TextBlock |
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| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LoansAndLeasesReceivableRealEstateAcquiredThroughForeclosurePolicy |