cm:Concept: us-gaap:SecuritiesSoldUnderAgreementsToRepurchaseAmountOffsetAgainstCollateral
| Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral |
| us-gaap:SecuritiesSoldUnderAgreementsToRepurchaseAmountOffsetAgainstCollateral |
| Amount, after effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price offset against a right to receive collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:SecuritiesSoldUnderAgreementsToRepurchaseAmountOffsetAgainstCollateral |