Investments - Consolidated Statements of Assets and Liabilities for PSSL (Parenthetical) (Details) - USD ($) $ in Thousands |
Jun. 30, 2026 |
Sep. 30, 2025 |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Investments at cost | $ 2,627,447 | [1],[2] | $ 2,819,393 | [3],[4],[5],[6] | ||||||||||||||||||
| Cash and cash equivalents, cost | 50,725 | 40,729 | ||||||||||||||||||||
| Cash equivalents at cost | 50,725 | 40,729 | ||||||||||||||||||||
| Cash At Cost | 50,090 | [7],[8],[9] | 81,955 | [5],[6] | ||||||||||||||||||
| Unfunded commitments to fund investments | 500 | 400 | ||||||||||||||||||||
| PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||||
| Investments at cost | 1,177,790 | 1,103,716 | ||||||||||||||||||||
| Cash equivalents at cost | 31,764 | 47,870 | ||||||||||||||||||||
| Cash At Cost | 20,292 | 13,690 | ||||||||||||||||||||
| 2036 Asset-Backed debt, net | 246,000 | 246,000 | ||||||||||||||||||||
| 2037 Asset-Backed debt, net | 246,000 | 246,000 | ||||||||||||||||||||
| 2037 R Asset-Backed debt, net | 246,000 | 246,000 | ||||||||||||||||||||
| PennantPark Senior Secured Loan Fund II LLC | ||||||||||||||||||||||
| Investments at cost | 320,825 | |||||||||||||||||||||
| Cash equivalents at cost | 4,901 | |||||||||||||||||||||
| Cash At Cost | 28,552 | |||||||||||||||||||||
| 2036 Asset-backed debt | PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||||
| Unamortized Deferred Financing Costs | 1,125 | 1,341 | ||||||||||||||||||||
| 2037 Asset-Backed Debt | PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||||
| Unamortized Deferred Financing Costs | 1,646 | 1,904 | ||||||||||||||||||||
| 2037 R Asset-backed debt | PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||||
| Unamortized Deferred Financing Costs | $ 2,185 | $ 2,518 | ||||||||||||||||||||
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