cm:Concept: us-gaap:CostMethodInvestmentsRealizedLosses
| Cost-method Investments, Realized Losses |
| us-gaap:CostMethodInvestmentsRealizedLosses |
| For investments in debt and equity securities accounted for at cost, the excess of the carrying amount over net sale proceeds of investments disposed of during the period and any losses recognized thereon for impairments of other than a temporary nature. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:CostMethodInvestmentsRealizedLosses |