Investments - Selected Balance Sheet Information for SLP III and SLP IV (Details) - USD ($) $ in Thousands |
Mar. 31, 2023 |
Dec. 31, 2022 |
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|---|---|---|---|---|---|---|---|---|
| Investment Company, Nonconsolidated Subsidiary [Line Items] | ||||||||
| Investments, cost | $ 3,302,614 | [1] | $ 3,259,967 | [2] | ||||
| Investments at fair value | 3,270,326 | [1] | 3,221,247 | [2] | ||||
| Total assets | 3,378,935 | 3,354,927 | ||||||
| Deferred financing costs, accumulated amortization | 49,187 | 47,531 | ||||||
| Deferred financing costs (net of accumulated amortization) | (16,699) | (17,199) | ||||||
| Other liabilities | 2,647 | 3,063 | ||||||
| Total liabilities | 2,040,441 | 2,028,736 | ||||||
| Total liabilities and net assets | 3,378,935 | 3,354,927 | ||||||
| SLP III | ||||||||
| Investment Company, Nonconsolidated Subsidiary [Line Items] | ||||||||
| Investments, cost | 684,051 | 681,288 | ||||||
| Investments at fair value | 651,129 | 639,327 | ||||||
| Cash and other assets | 19,548 | 17,149 | ||||||
| Receivable from unsettled securities sold | 8,816 | 0 | ||||||
| Total assets | 679,493 | 656,476 | ||||||
| Credit facility | 498,000 | 512,100 | ||||||
| Deferred financing costs, accumulated amortization | 5,211 | 4,840 | ||||||
| Deferred financing costs (net of accumulated amortization) | (1,325) | (1,695) | ||||||
| Payable for unsettled securities purchased | 28,024 | 0 | ||||||
| Distribution payable | 5,578 | 5,688 | ||||||
| Other liabilities | 7,203 | 6,492 | ||||||
| Total liabilities | 537,480 | 522,585 | ||||||
| Members' capital | 142,013 | 133,891 | ||||||
| Total liabilities and net assets | 679,493 | 656,476 | ||||||
| SLP IV | ||||||||
| Investment Company, Nonconsolidated Subsidiary [Line Items] | ||||||||
| Investments, cost | 503,359 | 504,875 | ||||||
| Investments at fair value | 477,724 | 473,762 | ||||||
| Cash and other assets | 14,645 | 12,853 | ||||||
| Receivable from unsettled securities sold | 7,525 | 0 | ||||||
| Total assets | 499,894 | 486,615 | ||||||
| Credit facility | 355,937 | 365,537 | ||||||
| Deferred financing costs, accumulated amortization | 1,145 | 997 | ||||||
| Deferred financing costs (net of accumulated amortization) | (1,860) | (2,008) | ||||||
| Payable for unsettled securities purchased | 4,558 | 0 | ||||||
| Distribution payable | 17,592 | 4,648 | ||||||
| Other liabilities | 6,051 | 5,410 | ||||||
| Total liabilities | 382,278 | 373,587 | ||||||
| Members' capital | 117,616 | 113,028 | ||||||
| Total liabilities and net assets | $ 499,894 | $ 486,615 | ||||||
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