cm:Member: us-gaap:CumulativePreferredStockMember
| Cumulative Preferred Stock [Member] |
| us-gaap:CumulativePreferredStockMember |
| Preferred stock upon which unpaid dividends accumulate until paid to shareholders. Classified within stockholders' equity if nonredeemable or redeemable solely at the option of the issuer. Classified within temporary equity if redemption is outside the control of the issuer. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:CumulativePreferredStockMember |