v3.25.4

Organization - Additional Information (Details) - USD ($) $ in Thousands |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2022 | Jan. 31, 2022 | Oct. 31, 2021 | Apr. 30, 2021 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Debt Instrument [Line Items] |  |  |  |  |  |  |
Holding transferred | 100.00% |  |  |  |  |  |
Net realized gain (loss) on investments |  |  |  |  | $ (52,460) | $ (33,833) | $ (151,516)
PennantPark-TSO Senior Loan Fund II, LP |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Sale of investments to wholly owned subsidiary |  | $ 82,300 |  |  |  |  |
Sale of investments to wholly owned subsidiary in cash |  | 75,700 |  |  |  |  |
Sale of investments to wholly owned subsidiary in equity interest |  | $ 6,600 |  |  |  |  |
Percentage of outstanding class A units |  | 23.10% |  |  | 23.10% |  |
Net realized gain (loss) on investments |  | $ 200 |  |  |  |  |
Capital commitment |  |  |  |  | $ 15,000 |  |
Funded percentage |  |  |  |  | 100.00% |  |
Voting interest in general partnership |  |  |  |  | 4.99% |  |
2026 Notes |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Aggregate principal amount of notes issued |  |  |  | $ 150,000 |  |  |
Percentage of public offering price per notes issued |  |  |  | 99.40% |  |  |
Debt instrument, maturity date |  |  |  | May 01, 2026 |  |  |
Debt instrument, periodic payment |  |  |  | semi-annually |  |  |
Debt instrument, interest rate |  |  |  | 4.50% |  |  |
Basis points |  |  |  | 4.62 |  |  |
2026 Notes-2 |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Aggregate principal amount of notes issued |  |  | $ 165,000 |  |  |  |
Percentage of public offering price per notes issued |  |  | 99.40% |  |  |  |
Debt instrument, maturity date |  |  | Nov. 01, 2026 |  |  |  |
Debt instrument, periodic payment |  |  | semi-annually |  |  |  |
Debt instrument, interest rate |  |  | 4.00% |  |  |  |
Basis points |  |  | 4.12 |  |  |  |

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