v3.26.1
Transactions with Affiliated Companies - Summary of Transactions with Affiliated Companies (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2026
Mar. 31, 2025
Sep. 30, 2025
Sep. 30, 2024
Investments In And Advances To Affiliates [Line Items]            
Fair Value $ 2,580,281 [1],[2],[3],[4],[5]   $ 2,580,281 [1],[2],[3],[4],[5]   $ 2,773,328 [6],[7],[8],[9],[10]  
Net Change in Unrealized Appreciation (Depreciation) 12,208 $ (20,776) (20,079) $ (49,738)    
Net Realized Gains (Losses) (7,535) (3,477) (6,079) 23,197    
Marketplace Events, LLC            
Investments In And Advances To Affiliates [Line Items]            
Fair Value [11]   0   0   $ 57,107
Gross Additions [11]       4,214    
Gross Reductions [11]       (59,795)    
Net Change in Unrealized Appreciation (Depreciation) [11]       (24,337)    
Interest Income [11]       5,062    
Dividend/Other Income [11]       306    
Net Realized Gains (Losses) [11]       22,811    
PennantPark Senior Secured Loan Fund I LLC            
Investments In And Advances To Affiliates [Line Items]            
Fair Value 297,766 [12] 297,290 [13] 297,766 [12] 297,290 [13] 281,968 [12] 294,128 [13]
Gross Additions     39,375 [12] 21,875 [13]    
Gross Reductions     0 [12] 0 [13]    
Net Change in Unrealized Appreciation (Depreciation)     (23,577) [12] (18,713) [13]    
Interest Income     14,233 [12] 15,091 [13]    
Dividend/Other Income     10,194 [12] 8,750 [13]    
Net Realized Gains (Losses)     0 [12] 0 [13]    
PennantPark Senior Secured Loan Fund II LLC            
Investments In And Advances To Affiliates [Line Items]            
Fair Value [14] 93,504   93,504   0  
Gross Additions [14]     93,750      
Gross Reductions [14]     0      
Net Change in Unrealized Appreciation (Depreciation) [14]     (246)      
Interest Income [14]     2,264      
Dividend/Other Income [14]     900      
Net Realized Gains (Losses) [14]     0      
Controlled Affiliated Investments [Member]            
Investments In And Advances To Affiliates [Line Items]            
Fair Value $ 391,270 $ 297,290 391,270 297,290 $ 281,968 $ 351,235
Gross Additions     133,125 26,089    
Gross Reductions     0 (59,795)    
Net Change in Unrealized Appreciation (Depreciation)     (23,823) (43,050)    
Interest Income     16,497 20,153    
Dividend/Other Income     11,094 9,056    
Net Realized Gains (Losses)     $ 0 $ 22,811    
[1] All of our investments are not registered under the 1933 Act and have restrictions on resale.
[2] As of March 31, 2026, all investments were in U.S. companies and total cost, fair value, and percentage of Net Assets for the U.S companies were $2,646.4 million, $2,580.3 million, and 248.4%
[3] The provisions of the 1940 Act classify investments based on the level of control that we maintain in a particular portfolio company. As defined in the 1940 Act, a company is generally presumed to be “non-controlled” when we own 25% or less of the portfolio company’s voting securities and “controlled” when we own more than 25% of the portfolio company’s voting securities.
[4] The provisions of the 1940 Act classify investments further based on the level of ownership that we maintain in a particular portfolio company. As defined in the 1940 Act, a company is generally deemed as “non-affiliated” when we own less than 5% of a portfolio company’s voting securities and “affiliated” when we own 5% or more of a portfolio company’s voting securities.
[5] Valued based on our accounting policy (See Note 2).
[6] All of our investments are not registered under the 1933 Act and have restrictions on resale.
[7] As of September 30, 2025, all investments were in U.S companies and total cost, fair value, and percentage of Net Assets for the U.S. companies were $2,819.4 million, $2,773.3 million, and 258.1%
[8] The provisions of the 1940 Act classify investments based on the level of control that we maintain in a particular portfolio company. As defined in the 1940 Act, a company is generally presumed to be “non-controlled” when we own 25% or less of the portfolio company’s voting securities and “controlled” when we own more than 25% of the portfolio company’s voting securities.
[9] The provisions of the 1940 Act classify investments further based on the level of ownership that we maintain in a particular portfolio company. As defined in the 1940 Act, a company is generally deemed as “non-affiliated” when we own less than 5% of a portfolio company’s voting securities and “affiliated” when we own 5% or more of a portfolio company’s voting securities.
[10] Valued based on our accounting policy (See Note 2). The value of all securities was determined using significant unobservable inputs (See Note 5).
[11] Marketplace was sold during the Q1 2025 quarter.
[12] We and HL are the members of PSSL II, a joint venture formed as a Delaware limited liability company that is not consolidated by us for financial reporting purposes. The members of PSSL II make investments in PSSL II in the form of first lien secured debt and equity interests, and all portfolio and other material decisions regarding PSSL II must be submitted to PSSL II’s board of directors or investment committee, both of which are comprised of equal number of representatives from each the Company and HL. Because management of PSSL II is shared equally between us and HL, we do not believe we control PSSL II for purposes of the 1940 Act or otherwise.
[13] We and Kemper are the members of PSSL, a joint venture formed as a Delaware limited liability company that is not consolidated by us for financial reporting purposes. The members of PSSL make investments in PSSL in the form of first lien secured debt and equity interests, and all portfolio and other material decisions regarding PSSL must be submitted to PSSL’s board of directors or investment committee, both of which are comprised of two members appointed by each of us and Kemper. Because management of PSSL is shared equally between us and Kemper, we do not believe we control PSSL for purposes of the 1940 Act or otherwise.
[14] We and Kemper are the members of PSSL, a joint venture formed as a Delaware limited liability company that is not consolidated by us for financial reporting purposes. The members of PSSL make investments in PSSL in the form of first lien secured debt and equity interests, and all portfolio and other material decisions regarding PSSL must be submitted to PSSL’s board of directors or investment committee, both of which are comprised of two members appointed by each of us and Kemper. Because management of PSSL is shared equally between us and Kemper, we do not believe we control PSSL for purposes of the 1940 Act or otherwise