cm:Concept: us-gaap:DescriptionOfNatureAndEffectOfSignificantChangesDuringPeriodAffectingComparability
| Defined Contribution Plan, Nature and Effect of Change, Description |
| us-gaap:DescriptionOfNatureAndEffectOfSignificantChangesDuringPeriodAffectingComparability |
| Description of nature and effect of change affecting comparability of defined contribution plan. Includes, but is not limited to, change in rate of employer contributions, business combination, or divestiture. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfNatureAndEffectOfSignificantChangesDuringPeriodAffectingComparability |