cm:Concept: us-gaap:AlternativeInvestmentFairValueByFairValueHierarchyLevelAndNavExtensibleList
| Alternative Investment, Fair Value by Fair Value Hierarchy Level and NAV [Extensible List] |
| us-gaap:AlternativeInvestmentFairValueByFairValueHierarchyLevelAndNavExtensibleList |
| Indicates level, within fair value hierarchy and fair value measured at net asset value per share as practical expedient, of alternative investment. |
| cm:Concept |
| srt-types:extensibleListItemType |
| As Of (instant) |
| (no balance type) |
| false |
| us-gaap:AlternativeInvestmentFairValueByFairValueHierarchyLevelAndNavExtensibleList |