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

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.26.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Thousands
12 Months Ended
Mar. 31, 2026
USD ($)
segment
Mar. 31, 2025
USD ($)
Summary of Investment Holdings [Line Items]    
Cost $ 1,052,848 [1] $ 939,066 [2]
Fair Value $ 1,309,248 [1] 979,320 [2]
Number of reportable segments | segment 1  
B+T Group Acquisition, Inc., Edge Adhesives Holdings Inc., And J.R. Hobbs Co    
Summary of Investment Holdings [Line Items]    
Cost $ 40,300  
Cost percentage 5.40%  
Fair Value $ 9,100  
Fair value percentage 1.40%  
Edge Adhesives Holdings, Inc., J.R. Hobbs Co. and The Mountain    
Summary of Investment Holdings [Line Items]    
Cost   $ 90,200
Cost percentage   13.10%
Fair Value   $ 50,900
Fair value percentage   8.20%
Non-Control/Non-Affiliate investments    
Summary of Investment Holdings [Line Items]    
Investment owned, percent of voting securities 5.00%  
Cost $ 711,741 [3] $ 562,371 [4]
Fair Value 983,959 [3] 648,589 [4]
Affiliate investments    
Summary of Investment Holdings [Line Items]    
Cost 323,698 [5] 359,286 [6]
Fair Value $ 324,676 [5] 330,388 [6]
Affiliate investments | Minimum    
Summary of Investment Holdings [Line Items]    
Investment owned, percent of voting securities 5.00%  
Affiliate investments | Maximum    
Summary of Investment Holdings [Line Items]    
Investment owned, percent of voting securities 25.00%  
Control investments    
Summary of Investment Holdings [Line Items]    
Investment owned, percent of voting securities 25.00%  
Cost $ 17,409 [7] 17,409 [8]
Fair Value $ 613 [7] $ 343 [8]
[1] Cumulative gross unrealized appreciation for federal income tax purposes is $428.5 million; cumulative gross unrealized depreciation for federal income tax purposes is $173.7 million. Cumulative net unrealized appreciation is $254.8 million, based on a tax cost of $1.1 billion.
[2] Cumulative gross unrealized appreciation for federal income tax purposes is $183.3 million; cumulative gross unrealized depreciation for federal income tax purposes is $144.9 million. Cumulative net unrealized appreciation is $38.5 million, based on a tax cost of $940.9 million.
[3] Non-Control/Non-Affiliate investments, as defined by the 1940 Act, are those that are neither Control nor Affiliate investments and in which we own less than 5.0% of the issued and outstanding voting securities.
[4] Non-Control/Non-Affiliate investments, as defined by the 1940 Act, are those that are neither Control nor Affiliate investments and in which we own less than 5.0% of the issued and outstanding voting securities.
[5] Affiliate investments, as defined by the 1940 Act, are those that are not Control investments and in which we own, with the power to vote, between and inclusive of 5.0% and 25.0% of the issued and outstanding voting securities.
[6] Affiliate investments, as defined by the 1940 Act, are those that are not Control investments and in which we own, with the power to vote, between and inclusive of 5.0% and 25.0% of the issued and outstanding voting securities.
[7] Control investments, as defined by the 1940 Act, are those where we have the power to exercise a controlling influence over the management or policies of the portfolio company, which may include owning, with the power to vote, more than 25.0% of the issued and outstanding voting securities.
[8] Control investments, as defined by the 1940 Act, are those where we have the power to exercise a controlling influence over the management or policies of the portfolio company, which may include owning, with the power to vote, more than 25.0% of the issued and outstanding voting securities.