v3.26.1
Fair Value Measurements - Schedule of Reconciliation of the Beginning and Ending Balances for Investments at Fair Value that use Level 3 Inputs (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2026
USD ($)
investment
Mar. 31, 2025
USD ($)
investment
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Fair value, asset, recurring basis, still held, unrealized gain (loss), statement of income or comprehensive income [extensible enumeration] Unrealized gain (loss) of investments Unrealized gain (loss) of investments
Total net change in unrealized gain (loss) on investments attributable to Level 3 investments still held $ (23,454) $ (1,819)
Number of investments transferred from Level 3 to Level 1 | investment 0 0
Investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Balance at the beginning $ 5,819,610 $ 4,008,824
Purchases of investments and other adjustments to cost 391,509 725,943
Proceeds from principal payments and sales of investments (376,865) (211,363)
Reclassifications 0 0
Balance at the end 5,804,360 4,520,484
Investments | Net realized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (11,734) 118
Investments | Net change in unrealized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (18,160) (3,038)
Senior secured loans    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Balance at the beginning 5,090,861 3,491,117
Purchases of investments and other adjustments to cost 326,393 605,995
Proceeds from principal payments and sales of investments (353,487) (166,479)
Reclassifications (17,030) (514)
Balance at the end 5,029,403 3,925,239
Senior secured loans | Net realized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (11,514) 142
Senior secured loans | Net change in unrealized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (5,820) (5,022)
Unitranche secured loans    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Balance at the beginning 35,414 148,531
Purchases of investments and other adjustments to cost 18 343
Proceeds from principal payments and sales of investments (17,122) (44,548)
Reclassifications 0 0
Balance at the end 18,159 103,073
Unitranche secured loans | Net realized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings 0 0
Unitranche secured loans | Net change in unrealized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (151) (1,253)
Junior secured loans    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Balance at the beginning 277,025 177,677
Purchases of investments and other adjustments to cost 52,420 79,552
Proceeds from principal payments and sales of investments (4,565) (89)
Reclassifications 0 (1,584)
Balance at the end 320,109 254,222
Junior secured loans | Net realized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (265) 0
Junior secured loans | Net change in unrealized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings (4,506) (1,334)
Equity investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Balance at the beginning 416,310 191,499
Purchases of investments and other adjustments to cost 12,678 40,053
Proceeds from principal payments and sales of investments (1,691) (247)
Reclassifications 17,030 2,098
Balance at the end 436,689 237,950
Equity investments | Net realized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings 45 (24)
Equity investments | Net change in unrealized gain (loss) on investments    
Reconciliation of beginning and ending balances for investments at fair value that use Level 3 inputs    
Gains (losses) included in earnings $ (7,683) $ 4,571