cm:Concept: us-gaap:ResaleAgreementsCollateralRightsInEventOfDefaultRelatedToSecuritiesToBeResold
| Resale Agreements, Collateral Rights in Event of Default Related to Securities to be Resold |
| us-gaap:ResaleAgreementsCollateralRightsInEventOfDefaultRelatedToSecuritiesToBeResold |
| This describes the policy with regards to collateral in the event of a default by the counter party of a resale agreement. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ResaleAgreementsCollateralRightsInEventOfDefaultRelatedToSecuritiesToBeResold |