cm:Concept: us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAociForInvestmentTransferredFromAvailableForSaleToEquityMethodAfterTax
| Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Investment Transferred from Available-for-sale to Equity Method, after Tax |
| us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAociForInvestmentTransferredFromAvailableForSaleToEquityMethodAfterTax |
| Amount, after tax, of reclassification adjustment from accumulated other comprehensive income (loss) for unrealized gain (loss) of investment classified as available-for-sale transferred to equity method. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAociForInvestmentTransferredFromAvailableForSaleToEquityMethodAfterTax |