cm:Concept: us-gaap:IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1
| Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments |
| us-gaap:IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1 |
| Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:IncreaseDecreaseInFairValueOfInterestRateFairValueHedgingInstruments1 |