cm:Concept: us-gaap:ContractualMaturitiesTimeDeposits100000OrMoreThreeMonthsOrLess
| Contractual Maturities, Time Deposits, $100,000 or More, Three Months or Less |
| us-gaap:ContractualMaturitiesTimeDeposits100000OrMoreThreeMonthsOrLess |
| Amount of time deposit liabilities, including certificates of deposit, in denominations of $100,000 or more, maturing within three months or fewer from the balance sheet date. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:ContractualMaturitiesTimeDeposits100000OrMoreThreeMonthsOrLess |