v3.23.3
Portfolio Investments - Schedule of Financial Instruments Carried at Fair Value (Details) - USD ($)
$ in Thousands
Sep. 30, 2023
Sep. 30, 2022
Schedule of Investments [Line Items]    
Investments at fair value $ 2,892,420 $ 2,494,111
Cash equivalents 83,262 5,261
Derivative assets 4,910 6,789
Total assets at fair value 2,980,592 2,506,161
Derivative liability 47,519 41,969
Total liabilities at fair value 47,519 41,969
Carrying Value 1,600,731 1,301,043
Fair Value 1,588,201 1,277,105
Senior secured debt    
Schedule of Investments [Line Items]    
Investments at fair value 2,501,385 2,166,409
Subordinated debt securities, including JV debt instruments    
Schedule of Investments [Line Items]    
Investments at fair value 218,390 203,453
Preferred equity    
Schedule of Investments [Line Items]    
Investments at fair value 86,057 79,523
Equity Securities, Common And Warrants, Including JV Investments    
Schedule of Investments [Line Items]    
Investments at fair value 86,588 44,726
2027 Notes    
Schedule of Investments [Line Items]    
Carrying Value 306,412 304,052
Fair Value 301,784 294,028
Level 1    
Schedule of Investments [Line Items]    
Investments at fair value 4,317 4,053
Cash equivalents 83,262 5,261
Derivative assets 0 0
Total assets at fair value 87,579 9,314
Derivative liability 0 0
Total liabilities at fair value 0 0
Fair Value 0 0
Level 1 | Senior secured debt    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Level 1 | Subordinated debt securities, including JV debt instruments    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Level 1 | Preferred equity    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Level 1 | Equity Securities, Common And Warrants, Including JV Investments    
Schedule of Investments [Line Items]    
Investments at fair value 4,317 4,053
Level 1 | 2027 Notes    
Schedule of Investments [Line Items]    
Fair Value 0 0
Level 2    
Schedule of Investments [Line Items]    
Investments at fair value 239,313 299,868
Cash equivalents 0 0
Derivative assets 4,910 6,789
Total assets at fair value 244,223 306,657
Derivative liability 47,519 41,969
Total liabilities at fair value 47,519 41,969
Fair Value 878,201 577,105
Level 2 | Senior secured debt    
Schedule of Investments [Line Items]    
Investments at fair value 208,694 255,803
Level 2 | Subordinated debt securities, including JV debt instruments    
Schedule of Investments [Line Items]    
Investments at fair value 28,666 44,065
Level 2 | Preferred equity    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Level 2 | Equity Securities, Common And Warrants, Including JV Investments    
Schedule of Investments [Line Items]    
Investments at fair value 1,953 0
Level 2 | 2027 Notes    
Schedule of Investments [Line Items]    
Fair Value 301,784 294,028
Level 3    
Schedule of Investments [Line Items]    
Investments at fair value 2,619,912 2,169,475
Cash equivalents 0 0
Derivative assets 0 0
Total assets at fair value 2,619,912 2,169,475
Derivative liability 0 0
Total liabilities at fair value 0 0
Fair Value 710,000 700,000
Level 3 | Senior secured debt    
Schedule of Investments [Line Items]    
Investments at fair value 2,292,691 1,910,606
Level 3 | Subordinated debt securities, including JV debt instruments    
Schedule of Investments [Line Items]    
Investments at fair value 189,724 159,388
Level 3 | Preferred equity    
Schedule of Investments [Line Items]    
Investments at fair value 86,057 79,523
Level 3 | Equity Securities, Common And Warrants, Including JV Investments    
Schedule of Investments [Line Items]    
Investments at fair value 51,440 19,958
Level 3 | 2027 Notes    
Schedule of Investments [Line Items]    
Fair Value 0 0
Fair Value Measured at Net Asset Value Per Share    
Schedule of Investments [Line Items]    
Investments at fair value 28,878 20,715
Cash equivalents 0 0
Derivative assets 0 0
Total assets at fair value 28,878 20,715
Derivative liability 0 0
Total liabilities at fair value 0 0
Fair Value Measured at Net Asset Value Per Share | Senior secured debt    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Fair Value Measured at Net Asset Value Per Share | Subordinated debt securities, including JV debt instruments    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Fair Value Measured at Net Asset Value Per Share | Preferred equity    
Schedule of Investments [Line Items]    
Investments at fair value 0 0
Fair Value Measured at Net Asset Value Per Share | Equity Securities, Common And Warrants, Including JV Investments    
Schedule of Investments [Line Items]    
Investments at fair value $ 28,878 $ 20,715