Financial Highlights - Summary of Financial Highlights (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Investment Company, Financial Highlights [Abstract]
Net Asset Value Per Share, Beginning Balance		$ 7.56	[1]	$ 7.7		$ 8.98	$ 9.85	$ 7.84
Net investment income	[2]	0.71		0.92		1	0.66	0.54
Net realized and unrealized (loss) gain	[2]	(0.21)		(0.17)		(1.52)	(1.03)	1.94
Net (decrease) increase in net assets resulting from operations	[2]	0.5		0.75		(0.52)	(0.37)	2.48
Distribution of net investment income	[2],[3]	(0.96)		(0.88)		(0.76)	(0.56)	(0.48)
Distribution of realized gains	[2],[3]	0		0		0	0	0
Total distributions to stockholders		(0.96)		(0.88)		(0.76)	(0.56)	(0.48)
(Dilutive) effect of common stock issuance		0		(0.01)		0	0	0
Repurchase of common stock	[2]	0		0		0	0.06	0
Net Asset Value Per Share, Ending Balance		7.11	[1]	7.56	[1]	7.7	8.98	9.85
Per share market value, end of year		$ 6.71		$ 6.99		$ 6.58	$ 5.46	$ 6.49
Total return	[4]	10.21%		20.54%		13.64%	(8.42%)	120.98%
Shares outstanding at end of year		65,296,094		65,296,094		65,224,500	65,224,500	67,045,105
Ratios / Supplemental Data:
Ratio of operating expenses to average net assets	[5]	7.13%		7.73%		7.75%	4.17%	3.74%
Ratio of interest and expenses on debt to average net assets	[6]	8.56%		9.06%		7.55%	5.19%	3.73%
Ratio of total expenses to average net assets	[6]	15.69%		16.78%		15.30%	9.36%	7.47%
Ratio of net investment income to average net assets	[6]	9.47%		12.04%		12.56%	6.74%	6.04%
Net Assets at end of year		$ 463,950		$ 493,908		$ 502,187	$ 585,565	$ 660,144
Weighted average debt outstanding	[7]	$ 686,808		$ 693,573		$ 656,776	$ 695,267	$ 649,666
Weighted average debt per share	[2],[7]	$ 10.52		$ 10.63		$ 10.07	$ 10.49	$ 9.69
Asset coverage per unit	[8]	$ 1,627		$ 1,637		$ 1,952	$ 1,855	$ 2,208
Average market value per unit	[9]	$ 0		$ 0		$ 0	$ 0	$ 25.13
Portfolio turnover ratio		65.30%		43.99%		32.58%	70.41%	37.74%

[1] NAV per share is determined as of the last day in the relevant quarter and therefore may not reflect the NAV per share on the date of the high and low sales prices. The NAVs shown are based on outstanding shares at the end of each period.

[2] Based on the weighted average shares outstanding for the respective periods.

[3] The tax status of distributions is calculated in accordance with income tax regulations, which may differ from amounts determined under GAAP, and reported on Form 1099-DIV each calendar year

[4] Based on the change in market price per share during the period and assumes distributions, if any, are reinvested.

[5] Excludes debt related costs.

[6] Includes interest and expenses on debt (annualized) as well as Truist Credit Facility amendment and debt issuance costs, if any (not annualized).

[7] Includes SBA debentures outstanding

[8] The asset coverage ratio for a class of senior securities representing indebtedness is calculated as our consolidated total assets, less all liabilities and indebtedness not represented by senior securities, divided by the senior securities representing indebtedness at par (changed from fair value). This asset coverage ratio is multiplied by $1,000 to determine the asset coverage per unit. These amounts exclude SBA debentures from our asset coverage per unit computation pursuant to exemptive relief received from the SEC in June 2011.

[9] The average market value per unit is derived based on the daily closing price of the 2024 Notes trading on The Nasdaq Global Select Market under the symbol “PNNTG,” which were issued in increments of $25 per unit and commenced trading on September 30, 2019. The 2024 Notes were redeemed in full on November 13, 2021 and no amounts were outstanding as of September 30, 2025, or 2024.