cm:Concept: us-gaap:LifeSettlementContractsFairValueMethodUnrealizedGainLoss
| Life Settlement Contracts, Fair Value Method, Unrealized Gain (Loss) |
| us-gaap:LifeSettlementContractsFairValueMethodUnrealizedGainLoss |
| The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments in life settlement contracts held at each balance sheet date, that was included in earnings for the period. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:LifeSettlementContractsFairValueMethodUnrealizedGainLoss |