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