cm:Concept: us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeFairValueOfSecuritiesSoldOrRepledged
| Customer Securities for which Entity has Right to Sell or Repledge, Fair Value of Securities Sold or Repledged |
| us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeFairValueOfSecuritiesSoldOrRepledged |
| Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it has sold or re-pledged to counterparties as collateral. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeFairValueOfSecuritiesSoldOrRepledged |