cm:Concept: us-gaap:DefinedBenefitPlanEstimatedFutureEmployerContributionsInCurrentFiscalYearDescription
| Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year, Description |
| us-gaap:DefinedBenefitPlanEstimatedFutureEmployerContributionsInCurrentFiscalYearDescription |
| Description of contributions expected to be received by defined benefit plan from employer in current fiscal year. Includes, but is not limited to, range of expected contributions, required minimum contributions and whether expected contributions are discretionary or noncash. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DefinedBenefitPlanEstimatedFutureEmployerContributionsInCurrentFiscalYearDescription |