cm:Level3TextBlock: us-gaap:OtherRealEstateNonCoveredRollForwardTableTextBlock
| Other Real Estate, Non Covered, Roll Forward [Table Text Block] |
| us-gaap:OtherRealEstateNonCoveredRollForwardTableTextBlock |
| Tabular disclosure of the change in other real estate not covered under loss sharing agreements with the Federal Deposit Insurance Corporation (FDIC). Excludes real estate assets taken in settlement of troubled loans through surrender or foreclosure by banks. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:OtherRealEstateNonCoveredRollForwardTableTextBlock |