cm:Axis: us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis
| Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] |
| us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis |
| Information by maturity period remaining for repurchase agreements and similar transactions, for example, but not limited to, securities lending arrangements. Element name and standard label in Maturity [numeric lower end] to [numeric higher end] [date measure] [Member] or Maturity Greater Than [low end numeric value] [date measure] [Member] or Maturity Less Than [high end numeric value] [date measure] [Member] formats. |
| cm:Axis |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis |