cm:Concept: us-gaap:FederalFundsSoldAndSecuritiesBorrowedOrPurchasedUnderAgreementsToResellFairValueDisclosure
| Federal Funds Sold and Securities Borrowed or Purchased under Agreements to Resell, Fair Value Disclosure |
| us-gaap:FederalFundsSoldAndSecuritiesBorrowedOrPurchasedUnderAgreementsToResellFairValueDisclosure |
| Fair value portion of federal funds sold and securities borrowed or purchased under agreements to resell. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:FederalFundsSoldAndSecuritiesBorrowedOrPurchasedUnderAgreementsToResellFairValueDisclosure |