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Fair Value Measurements (Narrative) (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021
Fair Value Measurement [Line Items] |  |
Percentage of portfolio of unadjusted fair values obtained | 98.20% |
Three Private Equity Funds using NAV | $ 89,400,000 |
One Private Equity Fund using NAV | 2,000 |
Transfers, level 1 to level 2 to level 3 | 0 | $ 0
Unsecured Notes Two | Revolving Credit Facility |  |
Fair Value Measurement [Line Items] |  |
Drawn down amount under credit facility | 25,000,000 |
Unsecured notes |  |
Fair Value Measurement [Line Items] |  |
Debt instrument, face amount | $ 375,000,000 | 375,000,000
Minimum |  |
Fair Value Measurement [Line Items] |  |
Liquidating investment, remaining period | 1 year |
Maximum |  |
Fair Value Measurement [Line Items] |  |
Liquidating investment, remaining period | 10 years |
Private Equity Funds |  |
Fair Value Measurement [Line Items] |  |
Unfunded commitments | $ 9,000,000 | 32,000,000
Venture Capital Investments |  |
Fair Value Measurement [Line Items] |  |
One Private Equity Fund using NAV | 800,000 |
Level 2 | Commercial Mortgage Backed Securities |  |
Fair Value Measurement [Line Items] |  |
Holings in mortgage backed securities | $ 27,300,000 | $ 25,200,000

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