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Investments - Schedule of Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Total |  |
Fair value, beginning of period | $ 2,237,531 | $ 2,127,521
New investments | 624,436 | 568,446
Investment restructuring | (22,249) |
Transfers into (out of) Level 3, net | 2,703 | 1,886
Proceeds from sales of investments / return of capital | (86,264) | (259,205)
Loan origination fees received | (8,694) | (8,286)
Principal repayments received | (477,826) | (236,821)
Fair value, end of period | 2,244,908 | 2,237,531
Cost | 2,522,696 | 2,535,576
Total investments at fair value | $ 2,449,272 | $ 2,488,715
Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 100.00% | 100.00%
Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 100.00% | 100.00%
Sierra JV |  |
Total |  |
Cost | $ 36,083 | $ 85,304
Total investments at fair value | $ 33,422 | $ 79,599
Sierra JV | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 100.00% | 100.00%
Sierra JV | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 100.00% | 100.00%
Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 21,263 | $ 25,311
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income | Total payment-in-kind interest income
Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 752 | $ 1,584
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 11,569 | $ 8,122
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ (31,861) | $ (46,340)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments | Net realized gains (losses) on investments
Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ (26,452) | $ 55,313
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments | Net unrealized appreciation (depreciation) on investments
Senior debt and 1st lien notes |  |
Total |  |
Fair value, beginning of period | $ 1,593,797 | $ 1,591,356
New investments | 559,616 | 396,040
Investment restructuring | (27,652) |
Transfers into (out of) Level 3, net | (2,366) | (15,843)
Proceeds from sales of investments / return of capital | (75,275) | (246,902)
Loan origination fees received | (8,398) | (8,173)
Principal repayments received | (380,761) | (151,817)
Fair value, end of period | 1,625,501 | 1,593,797
Cost | 1,747,841 | 1,705,353
Total investments at fair value | $ 1,686,411 | $ 1,670,300
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 69.00% | 67.00%
Senior debt and 1st lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 69.00% | 67.00%
Senior debt and 1st lien notes | Sierra JV |  |
Total |  |
Cost | $ 36,083 | $ 85,304
Total investments at fair value | $ 33,389 | $ 79,599
Senior debt and 1st lien notes | Sierra JV | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 100.00% | 100.00%
Senior debt and 1st lien notes | Sierra JV | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 100.00% | 100.00%
Senior debt and 1st lien notes | Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 7,711 | $ 6,757
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income | Total payment-in-kind interest income
Senior debt and 1st lien notes | Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 637 | $ 668
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Senior debt and 1st lien notes | Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 10,313 | $ 7,420
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Senior debt and 1st lien notes | Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ (24,371) | $ (1,746)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments | Net realized gains (losses) on investments
Senior debt and 1st lien notes | Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ (27,750) | $ 16,037
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments | Net unrealized appreciation (depreciation) on investments
Equity shares |  |
Total |  |
Fair value, beginning of period | $ 374,572 | $ 283,067
New investments | 22,934 | 94,595
Investment restructuring | 15,023 |
Transfers into (out of) Level 3, net | (2,556) | 914
Proceeds from sales of investments / return of capital | (4,834) | (8,977)
Loan origination fees received | 0 | 0
Principal repayments received | 0 | 0
Fair value, end of period | 408,475 | 374,572
Cost | 360,691 | 320,335
Total investments at fair value | $ 409,129 | $ 374,704
Equity shares | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 14.00% | 13.00%
Equity shares | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 17.00% | 15.00%
Equity shares | Sierra JV |  |
Total |  |
Cost | $ 0 |
Total investments at fair value | $ 33 |
Equity shares | Sierra JV | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 0.00% |
Equity shares | Sierra JV | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 0.00% |
Equity shares | Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 9,884 | $ 8,677
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income | Total payment-in-kind interest income
Equity shares | Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Equity shares | Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Equity shares | Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ (1,171) | $ (590)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments | Net realized gains (losses) on investments
Equity shares | Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ (5,377) | $ (3,114)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments | Net unrealized appreciation (depreciation) on investments
Subordinated debt and 2nd lien notes |  |
Total |  |
Fair value, beginning of period | $ 223,798 | $ 234,214
New investments | 37,466 | 49,525
Investment restructuring | (9,620) |
Transfers into (out of) Level 3, net | 0 | 16,815
Proceeds from sales of investments / return of capital | (4,975) | (2,800)
Loan origination fees received | (296) | (113)
Principal repayments received | (94,066) | (83,986)
Fair value, end of period | 153,703 | 223,798
Cost | 184,043 | 256,850
Total investments at fair value | $ 165,455 | $ 238,215
Subordinated debt and 2nd lien notes | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 7.00% | 10.00%
Subordinated debt and 2nd lien notes | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 7.00% | 10.00%
Subordinated debt and 2nd lien notes | Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 3,668 | $ 9,877
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income | Total payment-in-kind interest income
Subordinated debt and 2nd lien notes | Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 115 | $ 916
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Subordinated debt and 2nd lien notes | Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 1,256 | $ 702
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Subordinated debt and 2nd lien notes | Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ (6,361) | $ (43,902)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments | Net realized gains (losses) on investments
Subordinated debt and 2nd lien notes | Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ 2,718 | $ 42,550
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments | Net unrealized appreciation (depreciation) on investments
Structured Product |  |
Total |  |
Fair value, beginning of period | $ 42,972 | $ 17,827
New investments | 549 | 28,286
Investment restructuring | 0 |
Transfers into (out of) Level 3, net | 7,625 | 0
Proceeds from sales of investments / return of capital | (935) | (526)
Loan origination fees received | 0 | 0
Principal repayments received | (2,999) | (1,018)
Fair value, end of period | 48,664 | 42,972
Cost | 89,543 | 107,314
Total investments at fair value | $ 79,548 | $ 93,038
Structured Product | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 4.00% | 4.00%
Structured Product | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 3.00% | 4.00%
Structured Product | Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income | Total payment-in-kind interest income
Structured Product | Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Structured Product | Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Structured Product | Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ 42 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments | Net realized gains (losses) on investments
Structured Product | Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ 1,410 | $ (1,597)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments | Net unrealized appreciation (depreciation) on investments
Equity warrants |  |
Total |  |
Fair value, beginning of period | $ 2,392 | $ 1,057
New investments | 0 | 0
Investment restructuring | 0 |
Transfers into (out of) Level 3, net | 0 | 0
Proceeds from sales of investments / return of capital | 0 | 0
Loan origination fees received | 0 | 0
Principal repayments received | 0 | 0
Fair value, end of period | 2,732 | 2,392
Cost | 76 | 76
Total investments at fair value | $ 2,732 | $ 2,392
Equity warrants | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 0.00% | 0.00%
Equity warrants | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 0.00% | 0.00%
Equity warrants | Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income | Total payment-in-kind interest income
Equity warrants | Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Equity warrants | Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 0 | $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees | Interest and other financing fees
Equity warrants | Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ 0 | $ (102)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments | Net realized gains (losses) on investments
Equity warrants | Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ 340 | $ 1,437
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments | Net unrealized appreciation (depreciation) on investments
Royalty Rights |  |
Total |  |
Fair value, beginning of period | $ 0 |
New investments | 3,871 |
Investment restructuring | 0 |
Transfers into (out of) Level 3, net | 0 |
Proceeds from sales of investments / return of capital | (245) |
Loan origination fees received | 0 |
Principal repayments received | 0 |
Fair value, end of period | 5,833 | $ 0
Cost | 3,627 |
Total investments at fair value | $ 5,833 |
Royalty Rights | Percentage of Total Portfolio, at Cost | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 0.00% |
Royalty Rights | Percentage of Total Portfolio, at Fair Value | Investment Type Concentration Risk |  |
Total |  |
Percent of Total Portfolio | 0.00% |
Royalty Rights | Payment-in-kind interest / dividends |  |
Total |  |
Realized gain (loss) | $ 0 |
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Total payment-in-kind interest income |
Royalty Rights | Accretion of loan premium / discount |  |
Total |  |
Realized gain (loss) | $ 0 |
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees |
Royalty Rights | Accretion of deferred loan origination revenue |  |
Total |  |
Realized gain (loss) | $ 0 |
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Interest and other financing fees |
Royalty Rights | Realized gain (loss) |  |
Total |  |
Realized gain (loss) | $ 0 |
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net realized gains (losses) on investments |
Royalty Rights | Unrealized appreciation (depreciation) |  |
Total |  |
Realized gain (loss) | $ 2,207 |
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] | Net unrealized appreciation (depreciation) on investments |

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