cm:Concept: us-gaap:AssetsNeededForImmediateSettlementAggregateFairValue
| Assets Needed for Immediate Settlement, Aggregate Fair Value |
| us-gaap:AssetsNeededForImmediateSettlementAggregateFairValue |
| The aggregate fair value of assets needed to immediately settle the derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:AssetsNeededForImmediateSettlementAggregateFairValue |