cm:Member: us-gaap:NoncumulativePreferredStockSubjectToMandatoryRedemptionMember
| Noncumulative Preferred Stock Subject to Mandatory Redemption [Member] |
| us-gaap:NoncumulativePreferredStockSubjectToMandatoryRedemptionMember |
| Shares that embody an unconditional obligation requiring the issuer to redeem the securities by transferring the assets at a specified or determinable date (or dates) or upon an event that is certain to occur, which provide a specific dividend that is paid before any dividends are paid to common stock holders, which take precedence over common stock in the event of a liquidation, which do not enjoy any of the voting rights of common stockholders and which do not accrue unpaid dividends. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:NoncumulativePreferredStockSubjectToMandatoryRedemptionMember |