cm:Member: us-gaap:SeriesGPreferredStockMember
| Series G Preferred Stock [Member] |
| us-gaap:SeriesGPreferredStockMember |
| Outstanding nonredeemable series G preferred stock or outstanding series G preferred stock. 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:SeriesGPreferredStockMember |