v3.26.1
Fair Value Measurements - Changes in Fair Value of Investments Measured Using Level 3 Inputs (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Total                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Fair value, beginning of period $ 13,282,835 $ 13,036,526 $ 13,282,835 $ 13,036,526 $ 13,742,137 $ 14,100,239 $ 12,602,272 $ 12,976,765
Purchases of investments 419,547 549,363 766,871 1,267,152        
Proceeds from principal repayments and sales of investments (808,851) (164,206) (1,258,080) (1,162,200)        
Accretion of discount (amortization of premium) 12,893 10,523 23,955 26,607        
Transfers into level 3 95,767 0 0 225        
Transfers out of level 3 (9,124) 0 (9,146) (102,175)        
Fair value, end of period 13,282,835 13,036,526 13,282,835 13,036,526        
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations (173,609) 40,119 (328,647) 29,549        
Investments, Realized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) (31,316) (1,232) (30,261) 7,103        
Investments, Unrealized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) (138,218) 39,806 (310,743) 23,049        
First lien debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Fair value, beginning of period 12,863,118 12,800,357 12,863,118 12,800,357 13,409,419 13,759,817 12,370,969 12,714,636
Purchases of investments 326,223 546,760 670,142 1,262,249        
Proceeds from principal repayments and sales of investments (800,453) (163,314) (1,246,323) (1,128,141)        
Accretion of discount (amortization of premium) 12,730 10,437 23,663 26,437        
Transfers into level 3 95,767 0 0 225        
Transfers out of level 3 (9,124) 0 (9,146) (102,175)        
Fair value, end of period 12,863,118 12,800,357 12,863,118 12,800,357        
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations (168,224) 37,050 (315,044) 30,042        
Debt Securities, First Lien, Realized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) (38,695) (1,232) (38,565) (212)        
Debt Securities, First Lien, Unrealized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) (132,749) 36,737 (296,470) 27,338        
Second lien debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Fair value, beginning of period 250,182 122,942 250,182 122,942 228,827 231,650 118,482 119,184
Purchases of investments 22,646 2,123 25,114 3,787        
Proceeds from principal repayments and sales of investments (540) (662) (2,040) (3,010)        
Accretion of discount (amortization of premium) 153 75 273 149        
Transfers into level 3 0 0 0 0        
Transfers out of level 3 0 0 0 0        
Fair value, end of period 250,182 122,942 250,182 122,942        
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations (911) 2,924 (4,822) 2,347        
Debt Securities, Second Lien, Realized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) 7 0 7 (1)        
Debt Securities, Second Lien, Unrealized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) (911) 2,924 (4,822) 2,833        
Unsecured debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Fair value, beginning of period 12,348 13,721 12,348 13,721 12,502 12,278 13,658 33,521
Purchases of investments 493 471 1,427 939        
Proceeds from principal repayments and sales of investments 0 0 0 (20,595)        
Accretion of discount (amortization of premium) 10 11 19 21        
Transfers into level 3 0 0 0 0        
Transfers out of level 3 0 0 0 0        
Fair value, end of period 12,348 13,721 12,348 13,721        
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations (657) (419) (1,376) (435)        
Unsecured Debt, Realized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) 0 0 0 0        
Unsecured Debt, Unrealized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) (657) (419) (1,376) (165)        
Investments in equity                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Fair value, beginning of period 157,187 99,506 157,187 99,506 $ 91,389 $ 96,494 $ 99,163 $ 109,424
Purchases of investments 70,185 9 70,188 177        
Proceeds from principal repayments and sales of investments (7,858) (230) (9,717) (10,454)        
Accretion of discount (amortization of premium) 0 0 0 0        
Transfers into level 3 0 0 0 0        
Transfers out of level 3 0 0 0 0        
Fair value, end of period 157,187 99,506 157,187 99,506        
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the condensed consolidated statements of operations (3,817) 564 (7,405) (2,405)        
Equity Securities, Realized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) 7,372 0 8,297 7,316        
Equity Securities, Unrealized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Net realized gain (loss) $ (3,901) $ 564 $ (8,075) $ (6,957)