v3.25.1
Investments - Rollforward of Level 3 Investments Measured at Fair Value (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance $ 675,633 $ 800,775
Funding and purchases of investments, at cost 28,537 13,716
Principal payments and sale proceeds received from investments (29,971) (38,760)
Gross transfers out of Level 3 0 0
Fair value, ending balance 681,482 771,599
Net change in unrealized gains (losses) on Level 3 investments held $ (217) $ (4,268)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income Flag Net change in unrealized gains (losses) on investments Net change in unrealized gains (losses) on investments
Net amortization and accretion of premiums and discounts and end-of-term payments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ 1,467 $ 404
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income Flag Interest expense and amortization of fees Interest expense and amortization of fees
Net realized gains (losses) on investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ 2,278 $ (8,950)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income Flag Net realized gains (losses) on investments Net realized gains (losses) on investments
Net change in unrealized gains (losses) included in earnings    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ (217) $ 626
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income Flag Net change in unrealized gains (losses) on investments Net change in unrealized gains (losses) on investments
Payment-in-kind coupon    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ 3,755 $ 3,788
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income Flag Payment-in-kind interest income Payment-in-kind interest income
Debt investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance $ 560,105 $ 730,295
Funding and purchases of investments, at cost 27,327 13,155
Principal payments and sale proceeds received from investments (27,663) (38,755)
Gross transfers out of Level 3 0 0
Fair value, ending balance 565,413 695,191
Net change in unrealized gains (losses) on Level 3 investments held 422 (9,828)
Debt investments | Net amortization and accretion of premiums and discounts and end-of-term payments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 1,467 404
Debt investments | Net realized gains (losses) on investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 (8,937)
Debt investments | Net change in unrealized gains (losses) included in earnings    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 422 (4,759)
Debt investments | Payment-in-kind coupon    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 3,755 3,788
Warrant investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 39,963 30,055
Funding and purchases of investments, at cost 762 165
Principal payments and sale proceeds received from investments 0 (5)
Gross transfers out of Level 3 0 0
Fair value, ending balance 41,997 32,653
Net change in unrealized gains (losses) on Level 3 investments held 1,272 2,626
Warrant investments | Net amortization and accretion of premiums and discounts and end-of-term payments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Warrant investments | Net realized gains (losses) on investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 (13)
Warrant investments | Net change in unrealized gains (losses) included in earnings    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 1,272 2,451
Warrant investments | Payment-in-kind coupon    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Equity investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 75,565 40,425
Funding and purchases of investments, at cost 448 396
Principal payments and sale proceeds received from investments (2,308) 0
Gross transfers out of Level 3 0 0
Fair value, ending balance 74,072 43,755
Net change in unrealized gains (losses) on Level 3 investments held (1,911) 2,934
Equity investments | Net amortization and accretion of premiums and discounts and end-of-term payments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Equity investments | Net realized gains (losses) on investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 2,278 0
Equity investments | Net change in unrealized gains (losses) included in earnings    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (1,911) 2,934
Equity investments | Payment-in-kind coupon    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ 0 $ 0