Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Narrative (Details)

v3.26.1
INVESTMENTS - Narrative (Details)
$ in Thousands
 6 Months Ended 12 Months Ended
Mar. 31, 2026
USD ($)
portfolioCompany
state
industry
Sep. 30, 2025
USD ($)
Summary of Investment Holdings [Line Items]    
Number of investment portfolio company | portfolioCompany 55  
Number of states which have invested in the company location | state 22  
Number of industries that have made investments | industry 17  
Investments, at fair value $ 906,844 $ 859,124 [1]
Weighted average investment owned, at cost, amount $ 16,800 15,900
Uncollectible receivables allowance, minimum required day for uncollectible adjustment 90 days  
Gross receivables from portfolio companies $ 2,900 2,400
Allowance for uncollectible receivables 66 52
Five Largest Portfolio Investments | Investment Portfolio Benchmark | Customer Concentration Risk    
Summary of Investment Holdings [Line Items]    
Investments, at fair value $ 208,800 $ 196,500
Concentration risk, percentage 23.00% 22.90%
[1] Cumulative gross unrealized depreciation for federal income tax purposes is $59.7 million; cumulative gross unrealized appreciation for federal income tax purposes is $34.1 million. Cumulative net unrealized depreciation is $25.5 million, based on a tax cost of $884.7 million.