cm:Concept: us-gaap:UnrealizedGainLossOnPriceRiskFairValueHedgingInstruments
| Unrealized Gain (Loss) on Price Risk Fair Value Hedging Instruments |
| us-gaap:UnrealizedGainLossOnPriceRiskFairValueHedgingInstruments |
| Amount of unrealized gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives instruments 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:UnrealizedGainLossOnPriceRiskFairValueHedgingInstruments |