cm:Concept: us-gaap:TransferOfFinancialAssetsAccountedForAsSalesDescriptionOfChangeInAmount
| Transfer of Financial Assets Accounted for as Sales, Description of Change in Amount |
| us-gaap:TransferOfFinancialAssetsAccountedForAsSalesDescriptionOfChangeInAmount |
| Description of change to the amount of derecognized financial assets from transactions which comprise an initial transfer and an agreement entered into in contemplation of the initial transfer resulting in retention of substantially all of the exposure to the economic return throughout the term of the transaction. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:TransferOfFinancialAssetsAccountedForAsSalesDescriptionOfChangeInAmount |