Agreements and Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | 13 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|---|
Feb. 05, 2019 |
Jan. 01, 2018 |
Dec. 31, 2017 |
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2026 |
Mar. 31, 2025 |
Feb. 04, 2019 |
Sep. 30, 2025 |
|
| Related Party Transaction [Line Items] | |||||||||
| Annual rate of base management fee | 1.00% | 1.50% | 1.50% | ||||||
| Base management fee percentage of total net assets | 200.00% | ||||||||
| Base management fee amendment description | on November 13, 2018, in connection with our board of directors’ approval of the application of the modified asset coverage requirements under the 1940 Act to the Company, our board of directors approved an amendment to the Investment Management Agreement reducing the Investment Adviser’s annual base management fee from 1.50% to 1.00% on gross assets that exceed 200% of the Company’s total net assets as of the immediately preceding quarter-end. This amendment became effective on February 5, 2019 with the amendment and restatement of the Investment Management Agreement on April 12, 2019. | ||||||||
| Base management fee calculation description | The base management fee is calculated based on the average adjusted gross assets at the end of the two most recently completed calendar quarters, and appropriately adjusted for any share issuances or repurchases during the current calendar quarter. | ||||||||
| Base management fee | $ 3,600 | $ 4,000 | $ 7,500 | $ 8,300 | |||||
| Incentive fee quarter hurdle rate | 1.75% | ||||||||
| Incentive fee annual hurdle rate | 7.00% | ||||||||
| Incentive fees on net investment income | 2,000 | 2,400 | $ 2,000 | 5,200 | |||||
| Description of incentive fee on net investment income | We pay the Investment Adviser an incentive fee with respect to our Pre- Incentive Fee Net Investment Income in each calendar quarter as follows: (1) no incentive fee in any calendar quarter in which our Pre-Incentive Fee Net Investment Income does not exceed the hurdle rate of 1.75%, (2) 100% of our Pre-Incentive Fee Net Investment Income with respect to that portion of such Pre-Incentive Fee Net Investment Income, if any, that exceeds the hurdle rate but is less than 2.1212% in any calendar quarter (8.4848% annualized), and (3) 17.5% of the amount of our Pre-Incentive Fee Net Investment Income, if any, that exceeds 2.1212% in any calendar quarter. | ||||||||
| Incentive fee on capital gains percentage | 17.50% | 20.00% | 17.50% | ||||||
| Incentive fee on capital gains accrued | $ 0 | 0 | |||||||
| Administrative services expenses | 1,000 | 1,150 | 1,850 | 2,400 | |||||
| Receivable | 100 | 100 | $ 200 | ||||||
| PSLF | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Administrative services expenses | 441 | 300 | 784 | 696 | |||||
| Net investment income | 9,300 | 154,400 | 138,200 | 441,000 | |||||
| Realized gains on sale of investment | 100 | 100 | 400 | 900 | |||||
| PennantPark-TSO Senior Loan Fund II, LP | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Net investment income | 0 | 0 | |||||||
| Realized gains on sale of investment | 0 | 0 | 0 | 0 | |||||
| Investment Administrator | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Administrative services expenses | $ 400 | $ 300 | $ 800 | $ 700 | |||||
| Incentive Fee Payment Condition One | Maximum | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Incentive fee quarter hurdle rate | 1.75% | ||||||||
| Incentive Fee Payment Condition Two | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Pre-incentive fee net investment income percentage | 100.00% | ||||||||
| Incentive Fee Payment Condition Two | Maximum | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Incentive fee quarter hurdle rate | 2.1212% | ||||||||
| Incentive fee annual hurdle rate | 8.4848% | ||||||||
| Incentive Fee Payment Condition Three | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Pre-incentive fee net investment income percentage | 17.50% | ||||||||
| Incentive Fee Payment Condition Three | Minimum | |||||||||
| Related Party Transaction [Line Items] | |||||||||
| Incentive fee quarter hurdle rate | 2.1212% | ||||||||