cm:Concept: us-gaap:GainLossOnForeignCurrencyFairValueHedgeDerivatives
| Gain (Loss) on Foreign Currency Fair Value Hedge Derivatives |
| us-gaap:GainLossOnForeignCurrencyFairValueHedgeDerivatives |
| Amount of gain (loss) from the increase (decrease) in fair value of foreign currency derivatives and nonderivative instruments designated as fair value hedging instruments which were recognized in earnings, net of offsets by the gain (loss) on the hedged item to the extent that the fair value hedge was determined to be effective. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:GainLossOnForeignCurrencyFairValueHedgeDerivatives |