cm:Concept: us-gaap:IncreaseDecreaseInPayablesToBrokerDealers
| Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations |
| us-gaap:IncreaseDecreaseInPayablesToBrokerDealers |
| The increase (decrease) during the reporting period in the aggregate amount of obligations incurred arising from transactions with broker-dealers, such as amounts due on margin and unsettled cash transactions; includes payables to brokers, dealers and clearing organizations. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:IncreaseDecreaseInPayablesToBrokerDealers |