cm:Concept: us-gaap:HedgedAssetDiscontinuedFairValueHedgeCumulativeIncreaseDecrease
| Hedged Asset, Discontinued Fair Value Hedge, Cumulative Increase (Decrease) |
| us-gaap:HedgedAssetDiscontinuedFairValueHedgeCumulativeIncreaseDecrease |
| Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, remaining after discontinued hedge. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:HedgedAssetDiscontinuedFairValueHedgeCumulativeIncreaseDecrease |