cm:Concept: us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionBeforeTaxAfterReclassificationAdjustmentAttributableToNoncontrollingInterest
| Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, before Tax, after Reclassification Adjustment, Attributable to Noncontrolling Interest |
| us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionBeforeTaxAfterReclassificationAdjustmentAttributableToNoncontrollingInterest |
| Amount, before tax, after 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:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionBeforeTaxAfterReclassificationAdjustmentAttributableToNoncontrollingInterest |