cm:Concept: us-gaap:NoncontrollingInterestInNetIncomeLossOperatingPartnershipsNonredeemable
| Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Nonredeemable |
| us-gaap:NoncontrollingInterestInNetIncomeLossOperatingPartnershipsNonredeemable |
| Amount after tax of income (loss) attributable to nonredeemable noncontrolling partner in an operating partnership. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:NoncontrollingInterestInNetIncomeLossOperatingPartnershipsNonredeemable |