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Percentage of unadjusted fair value obtained

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Remaining period of expected liquidation by investee of underlying asset of investment measured at net asset value per share or unit. In 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

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Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Fair Value Measurement (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
Fair Value Measurement (Narrative) (Details) - USD ($)	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Percentage of portfolio of unadjusted fair values obtained	98.10%
Three private equity funds using NAV	$ 92,900,000
Fair Value, Assets, Level 1 to Level 2 to Level 3 Transfers, Amount	0	$ 0
Unsecured Notes Two \| Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Drawn down amount under credit facility	$ 75,000,000		$ 25,000,000
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, liquidating investment, remaining period	1 year
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, liquidating investment, remaining period	10 years
Technology, Healthcare, Specialty Customer Goods and Service
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
One private equity fund using NAV	$ 500
Venture Capital Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
One private equity fund using NAV	1,000,000
Private Equity Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unfunded commitments to VIEs	9,000,000		9,000,000
Level 2 \| Unsecured debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured notes	375,000,000		375,000,000
Level 2 \| Commercial Mortgage Back Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, trading, and equity securities, FV-NI	$ 26,900,000		$ 27,300,000