cm:Concept: us-gaap:FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResellPledgedAsCollateral
| Federal Funds Sold and Securities Purchased under Agreements to Resell Pledged as Collateral |
| us-gaap:FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResellPledgedAsCollateral |
| The fair value of federal funds sold and securities purchased under agreements to resell that serve as collateral for borrowings. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResellPledgedAsCollateral |