cm:Member: us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeSecuritiesTypeDomain
| Customer Securities for which Entity has Right to Sell or Repledge, Securities Type [Domain] |
| us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeSecuritiesTypeDomain |
| Description of financial instrument type of customer securities accepted by the entity and re-pledged to counterparties as collateral or sold. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeSecuritiesTypeDomain |