cm:Level3TextBlock: us-gaap:ScheduleOfActivityInAffordableHousingProgramObligationTableTextBlock
| Activity in Affordable Housing Program Obligation [Table Text Block] |
| us-gaap:ScheduleOfActivityInAffordableHousingProgramObligationTableTextBlock |
| Tabular disclosure of the activity in the Affordable Housing Program (AHP) obligation. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfActivityInAffordableHousingProgramObligationTableTextBlock |