v3.26.1
Fair Value Measurements - Reconciliation of investments (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Fair Value Measurements    
Beginning Balance $ 2,443,312 $ 2,354,678
Purchases of investments and other adjustments to cost 235,800 1,280,957
Paid-in-kind interest 7,385 33,881
Net accretion of discounts (amortization of premiums) 1,745 5,139
Principal repayments and sales of investments (255,103) (1,231,175)
Net change in unrealized appreciation on investments (4,476) 28,048
Net realized gain (loss) on investments (9,629) (28,216)
Ending Balance 2,419,034 2,443,312
Change in unrealized appreciation attributable to investments still held (14,802) 456
First Lien Senior Secured Loans    
Fair Value Measurements    
Beginning Balance 1,591,538 1,543,286
Purchases of investments and other adjustments to cost 222,532 1,170,550
Paid-in-kind interest 4,290 19,831
Net accretion of discounts (amortization of premiums) 1,539 4,875
Principal repayments and sales of investments (182,991) (1,132,193)
Net change in unrealized appreciation on investments (13,273) (2,937)
Net realized gain (loss) on investments 316 (11,874)
Ending Balance 1,623,951 1,591,538
Change in unrealized appreciation attributable to investments still held (13,224) (14,211)
Second Lien Senior Secured Loans    
Fair Value Measurements    
Beginning Balance 30,020 30,104
Purchases of investments and other adjustments to cost   9,670
Net accretion of discounts (amortization of premiums) 28 64
Principal repayments and sales of investments   (9,597)
Net change in unrealized appreciation on investments 21 18,817
Net realized gain (loss) on investments   (19,038)
Ending Balance 30,069 30,020
Change in unrealized appreciation attributable to investments still held 21 (62)
Subordinated Debt    
Fair Value Measurements    
Beginning Balance 95,687 53,350
Purchases of investments and other adjustments to cost   29,393
Paid-in-kind interest 2,745 10,159
Net accretion of discounts (amortization of premiums) 175 203
Principal repayments and sales of investments (13,725)  
Net change in unrealized appreciation on investments (3,686) (2,486)
Net realized gain (loss) on investments 525  
Reclassifications   5,068
Ending Balance 81,721 95,687
Change in unrealized appreciation attributable to investments still held (3,065) (2,581)
Preferred Equity    
Fair Value Measurements    
Beginning Balance 157,244 170,876
Purchases of investments and other adjustments to cost 4,003 33,316
Paid-in-kind interest 350 3,891
Net accretion of discounts (amortization of premiums) 3 3
Principal repayments and sales of investments   (63,294)
Net change in unrealized appreciation on investments 3,500 6,442
Net realized gain (loss) on investments   11,078
Reclassifications   (5,068)
Ending Balance 165,100 157,244
Change in unrealized appreciation attributable to investments still held 3,500 13,107
Equity Interests    
Fair Value Measurements    
Beginning Balance 219,124 219,210
Purchases of investments and other adjustments to cost 280 14,528
Net accretion of discounts (amortization of premiums)   (6)
Principal repayments and sales of investments (58,387) (26,091)
Net change in unrealized appreciation on investments 9,239 19,865
Net realized gain (loss) on investments (10,470) (8,382)
Ending Balance 159,786 219,124
Change in unrealized appreciation attributable to investments still held (1,757) 15,856
Warrants    
Fair Value Measurements    
Beginning Balance 1,045 628
Net change in unrealized appreciation on investments (277) 417
Ending Balance 768 1,045
Change in unrealized appreciation attributable to investments still held (277) 417
Subordinated Note Investment Vehicles    
Fair Value Measurements    
Beginning Balance 348,654 [1] 337,224 [2]
Purchases of investments and other adjustments to cost 8,985 [1] 23,500 [2]
Net change in unrealized appreciation on investments [2]   (12,070)
Ending Balance [1] $ 357,639 348,654
Change in unrealized appreciation attributable to investments still held [2]   $ (12,070)
[1] Represents debt investment in ISLP and SLP.
[2] Represents debt investment in ISLP and SLP.