cm:Concept: us-gaap:HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease
| Hedged Asset, Fair Value Hedge, Last-of-Layer, Cumulative Increase (Decrease) |
| us-gaap:HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease |
| Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, in last-of-layer hedging relationship. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease |