cm:Concept: us-gaap:ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1
| Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments |
| us-gaap:ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1 |
| Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1 |