Annual report [Section 13 and 15(d), not S-K Item 405]

BORROWINGS - Revolving Line of Credit Narrative (Details)

v3.25.3
BORROWINGS - Revolving Line of Credit Narrative (Details) - Credit Facility - Revolving Line of Credit - Line of Credit
$ in Thousands
 12 Months Ended
Sep. 30, 2025
USD ($)
obligor
Sep. 30, 2024
USD ($)
Debt Instrument [Line Items]    
Line of credit facility, maximum borrowing capacity $ 320,000 $ 293,659
Line of credit facility, accordion feature maximum borrowing capacity $ 400,000  
Debt instrument, basis spread on variable rate 2.60% 3.10%
Debt instrument, covenant, borrowing base, minimum number of obligors | obligor 25  
Covenant, required minimum net worth of mandatory redeemable term preferred stock $ 500,000  
Covenant, required minimum net worth of mandatory redeemable term preferred stock, plus percent of all equity and subordinated debt raised 50.00%  
Covenant, required minimum net worth of mandatory redeemable term preferred stock, minus percent of any equity or subordinated debt redeemed or retired 50.00%  
Covenant, required minimum net worth of mandatory redeemable term preferred stock, plus percent of all equity and subordinated debt raised, minus percent of any equity or subordinated debt redeemed or retired $ 581,000  
Debt instrument, covenant, senior security, indebtedness, required minimum asset coverage ratio 150.00%  
Senior security, indebtedness, asset coverage amount $ 877,900  
Indebtedness asset coverage on our senior securities 219.80%  
Investment company, number of obligor | obligor 34  
SOFR, Tranche One    
Debt Instrument [Line Items]    
Debt instrument, basis spread on variable rate 2.60%  
SOFR, Thereafter    
Debt Instrument [Line Items]    
Debt instrument, basis spread on variable rate 3.10%