cm:Member: us-gaap:VariableRateDemandObligationMember
| Variable Rate Demand Obligation [Member] |
| us-gaap:VariableRateDemandObligationMember |
| Debt securities that permit the holder to require the trustee or tender agent to repurchase the security at specified dates before maturity. This type of bond is also known as a multimaturity bond, an option tender bond, or a put bond. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:VariableRateDemandObligationMember |