cm:Concept: us-gaap:ContractualMaturitiesTimeDeposits100000OrMoreAfter12Months
| Contractual Maturities, Time Deposits, $100,000 or More, after 12 Months |
| us-gaap:ContractualMaturitiesTimeDeposits100000OrMoreAfter12Months |
| Amount of time deposit liabilities, including certificates of deposit, in denominations of $100,000 or more, maturing after twelve months from the balance sheet date. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:ContractualMaturitiesTimeDeposits100000OrMoreAfter12Months |