v3.23.3
Portfolio Investments - Summarized Statement of Operations Information (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Total investment income   $ 379,286 $ 262,520 $ 209,385
Interest expense   111,642 46,929 30,518
Total expenses   204,036 113,591 111,092
Net investment income before taxes   180,775 151,929 99,901
Net increase (decrease) in net assets resulting from operations   117,331 29,223 237,260
SLF JV I        
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Interest income   38,984 24,014 20,018
Fee income   290 198 565
Total investment income   39,274 24,212 20,583
Other expenses   442 253 260
Total expenses   33,988 17,112 14,410
Net investment income before taxes   5,286 7,100 6,173
Net unrealized appreciation (depreciation)   13,416 (23,661) 13,270
Realized gain (loss)   (10,962) 534 399
Net increase (decrease) in net assets resulting from operations   7,740 (16,027) 19,842
SLF JV I | Senior Credit Facility        
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Interest expense   19,002 7,713 5,706
SLF JV I | SLF JV I Notes        
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Interest expense   14,544 9,146 $ 8,444
OCSI Glick JV LLC        
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Interest income $ 4,643 14,043 9,703  
Fee income 67 63 149  
Total investment income 4,710 14,106 9,852  
Other expenses 95 182 168  
Total expenses 3,032 12,798 6,491  
Net investment income before taxes 1,678 1,308 3,361  
Net unrealized appreciation (depreciation) (1,710) 1,254 (3,216)  
Realized gain (loss) 32 (2,562) (145)  
Net increase (decrease) in net assets resulting from operations 0 0 0  
OCSI Glick JV LLC | Senior Credit Facility        
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Interest expense 1,157 6,560 2,747  
OCSI Glick JV LLC | Glick JV Notes        
Investment Company, Nonconsolidated Subsidiary [Line Items]        
Interest expense $ 1,780 $ 6,056 $ 3,576