cm:Concept: us-gaap:ConcentrationRiskCreditRiskUninsuredDeposits
| Concentration Risk, Credit Risk, Uninsured Deposits |
| us-gaap:ConcentrationRiskCreditRiskUninsuredDeposits |
| Description of credit risk that arises from having significant balances in excess of the Federal Deposit Insurance Corporation or other insurance limits on deposits in financial institutions. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ConcentrationRiskCreditRiskUninsuredDeposits |