cm:Concept: us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionReclassificationAdjustmentFromAociForDerecognitionAfterTax
| Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, after Tax |
| us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionReclassificationAdjustmentFromAociForDerecognitionAfterTax |
| Amount, after tax, of reclassification adjustment from accumulated other comprehensive income (loss) for unrealized gain (loss) from increase (decrease) in instrument-specific credit risk, realized upon derecognition of financial liability measured under fair value option. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionReclassificationAdjustmentFromAociForDerecognitionAfterTax |