cm:Member: us-gaap:FederalFundsSoldAndSecuritiesBorrowedOrPurchasedUnderAgreementsToResellMember
| Federal Funds Sold and Securities Borrowed or Purchased under Agreements to Resell [Member] |
| us-gaap:FederalFundsSoldAndSecuritiesBorrowedOrPurchasedUnderAgreementsToResellMember |
| Federal funds sold and securities borrowed or purchased under agreements to resell. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:FederalFundsSoldAndSecuritiesBorrowedOrPurchasedUnderAgreementsToResellMember |