cm:Concept: us-gaap:AverageCollectedCashBalancesWithCommercialBanksFederalHomeLoanBank
| Average Collected Cash Balances with Commercial Banks, Federal Home Loan Bank |
| us-gaap:AverageCollectedCashBalancesWithCommercialBanksFederalHomeLoanBank |
| Average amount of collected cash balances with commercial banks the Federal Home Loan Banks (FHLBanks) maintain in return for certain services. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:AverageCollectedCashBalancesWithCommercialBanksFederalHomeLoanBank |