cm:Concept: us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionAfterTaxAndReclassificationAdjustmentAttributableToNoncontrollingInterest
| Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, after Tax and Reclassification Adjustment, Attributable to Noncontrolling Interest |
| us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionAfterTaxAndReclassificationAdjustmentAttributableToNoncontrollingInterest |
| Amount, after tax and reclassification adjustment, of gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option, attributable to noncontrolling interest. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionAfterTaxAndReclassificationAdjustmentAttributableToNoncontrollingInterest |