Investments - Investment Cost and Fair Value by Type and by Industry (Details) - USD ($) $ in Thousands |
Mar. 31, 2023 |
Dec. 31, 2022 |
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|---|---|---|---|---|---|---|---|---|
| Schedule of Investments [Line Items] | ||||||||
| Cost | $ 3,302,614 | [1] | $ 3,259,967 | [2] | ||||
| Fair Value | 3,270,326 | [1] | 3,221,247 | [2] | ||||
| Software | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 951,994 | 916,259 | ||||||
| Fair Value | 933,923 | 897,008 | ||||||
| Business Services | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 639,640 | 661,079 | ||||||
| Fair Value | 577,406 | 592,868 | ||||||
| Healthcare | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 582,366 | 586,311 | ||||||
| Fair Value | 558,625 | 548,383 | ||||||
| Investment Funds (includes investments in joint ventures) | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 252,400 | 252,400 | ||||||
| Fair Value | 252,400 | 252,400 | ||||||
| Education | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 202,706 | 200,117 | ||||||
| Fair Value | 243,339 | 239,301 | ||||||
| Consumer Services | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 152,247 | 126,392 | ||||||
| Fair Value | 150,766 | 123,880 | ||||||
| Net Lease | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 96,041 | 96,041 | ||||||
| Fair Value | 120,623 | 120,986 | ||||||
| Distribution & Logistics | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 111,266 | 111,096 | ||||||
| Fair Value | 103,157 | 102,410 | ||||||
| Financial Services | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 98,346 | 96,021 | ||||||
| Fair Value | 99,197 | 95,839 | ||||||
| Energy | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 56,820 | 55,507 | ||||||
| Fair Value | 62,876 | 61,564 | ||||||
| Information Technology | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 58,654 | 58,638 | ||||||
| Fair Value | 58,865 | 58,165 | ||||||
| Specialty Chemicals & Materials | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 25,354 | 25,363 | ||||||
| Fair Value | 40,795 | 60,268 | ||||||
| Packaging | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 43,177 | 43,124 | ||||||
| Fair Value | 40,731 | 40,547 | ||||||
| Consumer Products | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 20,833 | 20,850 | ||||||
| Fair Value | 19,976 | 20,624 | ||||||
| Business Products | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 10,770 | 10,769 | ||||||
| Fair Value | 7,647 | 7,004 | ||||||
| First lien | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 1,862,802 | 1,816,091 | ||||||
| Fair Value | 1,798,746 | 1,753,967 | ||||||
| Second lien | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 616,660 | 632,990 | ||||||
| Fair Value | 562,413 | 561,207 | ||||||
| Subordinated | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 87,726 | 85,774 | ||||||
| Fair Value | 78,282 | 76,659 | ||||||
| Equity and other | ||||||||
| Schedule of Investments [Line Items] | ||||||||
| Cost | 735,426 | 725,112 | ||||||
| Fair Value | $ 830,885 | $ 829,414 | ||||||
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