cm:Axis: us-gaap:DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis
| Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Axis] |
| us-gaap:DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis |
| Information by type of deferred compensation related to other postretirement benefit arrangements that are not equivalent to a defined benefit other postretirement benefit plan. Includes, but is not limited to, employment contracts with one or more selected officers or key employees. Excludes equity-based compensation plans, defined benefit pension plans and defined benefit other postretirement benefit plans. |
| cm:Axis |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis |