cm:Concept: us-gaap:RealEstatePartnershipInvestmentSubsidiariesNetIncomeLossBeforeTax
| Real Estate Partnership Investment Subsidiaries, Net Income (Loss) before Tax |
| us-gaap:RealEstatePartnershipInvestmentSubsidiariesNetIncomeLossBeforeTax |
| Amount, before tax, of net income (loss) derived from real estate held for development and sale, and related investments. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:RealEstatePartnershipInvestmentSubsidiariesNetIncomeLossBeforeTax |