cm:Concept: us-gaap:PledgedAssetsSeparatelyReportedSecuritiesPledgedForFederalHomeLoanBankAtFairValue
| Pledged Assets Separately Reported, Securities Pledged for Federal Home Loan Bank, at Fair Value |
| us-gaap:PledgedAssetsSeparatelyReportedSecuritiesPledgedForFederalHomeLoanBankAtFairValue |
| The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of the FHLB debt obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:PledgedAssetsSeparatelyReportedSecuritiesPledgedForFederalHomeLoanBankAtFairValue |