Investments - Schedule of Investments by Industry Classification and Enumerates Percentage, by Fair Value, of Total Portfolio Assets Excluding Cash and Cash Equivalents (Details) - USD ($) $ in Thousands		Sep. 30, 2025		Sep. 30, 2024
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost		$ 1,236,888	[1]	$ 1,316,872	[2],[3]
Fair Value		$ 1,287,273	[1],[4]	$ 1,328,050	[2],[3],[5]
Net Asset Value Percentage		(188.60%)		(179.00%)	[2],[3]
Business Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 195,614		$ 205,232
Fair Value	[6]	$ 184,452		$ 184,233
Fair Value Percentage	[6]	17.00%		16.00%
Net Asset Value Percentage	[6]	40.00%		37.00%
Healthcare, Education and Childcare
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 128,969		$ 124,430
Fair Value	[6]	$ 168,000		$ 127,574
Fair Value Percentage	[6]	16.00%		11.00%
Net Asset Value Percentage	[6]	36.00%		26.00%
Distribution
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 57,352		$ 120,378
Fair Value	[6]	$ 130,850		$ 165,304
Fair Value Percentage	[6]	12.00%		14.00%
Net Asset Value Percentage	[6]	28.00%		33.00%
Short-Term U.S. Government Securities
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 124,809		$ 99,652
Fair Value	[6]	$ 124,788		$ 99,632
Fair Value Percentage	[6]	12.00%		8.00%
Net Asset Value Percentage	[6]	27.00%		20.00%
Financial Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 70,403		$ 69,915
Fair Value	[6]	$ 68,959		$ 71,527
Fair Value Percentage	[6]	6.00%		6.00%
Net Asset Value Percentage	[6]	15.00%		14.00%
Consumer Products
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 53,746		$ 89,773
Fair Value	[6]	$ 49,414		$ 89,743
Fair Value Percentage	[6]	5.00%		8.00%
Net Asset Value Percentage	[6]	11.00%		18.00%
Aerospace and Defense
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 39,513		$ 53,472
Fair Value	[6]	$ 47,113		$ 54,017
Fair Value Percentage	[6]	4.00%		5.00%
Net Asset Value Percentage	[6]	10.00%		11.00%
Environmental Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 61,588		$ 51,402
Fair Value	[6]	$ 31,238		$ 44,290
Fair Value Percentage	[6]	3.00%		4.00%
Net Asset Value Percentage	[6]	7.00%		9.00%
Auto Sector
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 26,621		$ 39,449
Fair Value	[6]	$ 27,826		$ 40,752
Fair Value Percentage	[6]	2.00%		4.00%
Net Asset Value Percentage	[6]	6.00%		8.00%
Personal, Food and Miscellaneous Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 16,207		$ 17,203
Fair Value	[6]	$ 18,769		$ 18,850
Fair Value Percentage	[6]	2.00%		2.00%
Net Asset Value Percentage	[6]	4.00%		4.00%
Media
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 17,477		$ 31,964
Fair Value	[6]	$ 17,434		$ 32,130
Fair Value Percentage	[6]	2.00%		3.00%
Net Asset Value Percentage	[6]	4.00%		7.00%
Gaming
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 22,853		$ 0
Fair Value	[6]	$ 23,151		$ 0
Fair Value Percentage	[6]	2.00%		0.00%
Net Asset Value Percentage	[6]	5.00%		0.00%
Telecommunications
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 22,305		$ 35,986
Fair Value	[6]	$ 13,695		$ 34,045
Fair Value Percentage	[6]	1.00%		3.00%
Net Asset Value Percentage	[6]	3.00%		7.00%
Diversified Conglomerate Service
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 17,268		$ 10,091
Fair Value	[6]	$ 16,416		$ 9,834
Fair Value Percentage	[6]	1.00%		1.00%
Net Asset Value Percentage	[6]	4.00%		2.00%
Consumer Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 19,067		$ 8,700
Fair Value	[6]	$ 19,319		$ 8,449
Fair Value Percentage	[6]	2.00%		1.00%
Net Asset Value Percentage	[6]	4.00%		2.00%
Manufacturing / Basic Industries
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 42,601		$ 12,686
Fair Value	[6]	$ 43,067		$ 12,713
Fair Value Percentage	[6]	4.00%		1.00%
Net Asset Value Percentage	[6]	9.00%		3.00%
Buildings and Real Estate
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 12,546		$ 12,515
Fair Value	[6]	$ 12,495		$ 12,442
Fair Value Percentage	[6]	1.00%		1.00%
Net Asset Value Percentage	[6]	3.00%		3.00%
Chemicals, Plastics and Rubber
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 15,237		$ 32,255
Fair Value	[6]	$ 12,240		$ 31,598
Fair Value Percentage	[6]	1.00%		3.00%
Net Asset Value Percentage	[6]	3.00%		6.00%
Event Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 11,823		$ 0
Fair Value	[6]	$ 12,073		$ 0
Fair Value Percentage	[6]	1.00%		0.00%
Net Asset Value Percentage	[6]	3.00%		0.00%
Home and Office Furnishings, Housewares and Durable Consumer Products [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 9,258		$ 9,663
Fair Value	[6]	$ 9,723		$ 9,663
Fair Value Percentage	[6]	1.00%		1.00%
Net Asset Value Percentage	[6]	2.00%		2.00%
Electronics
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 2,507		$ 14,887
Fair Value	[6]	$ 5,485		$ 19,633
Fair Value Percentage	[6]	1.00%		2.00%
Net Asset Value Percentage	[6]	1.00%		4.00%
Consulting Services
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 5,970		$ 0
Fair Value	[6]	$ 5,966		$ 0
Fair Value Percentage	[6]	1.00%		0.00%
Net Asset Value Percentage	[6]	1.00%		0.00%
Other
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 40,509		$ 93,898
Fair Value	[6]	$ 37,000		$ 77,812
Fair Value Percentage	[6]	3.00%		7.00%
Net Asset Value Percentage	[6]	8.00%		16.00%
Total Industry [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Cost	[6]	$ 1,014,243		$ 1,133,551
Fair Value	[6]	$ 1,079,473		$ 1,144,241
Fair Value Percentage	[6]	100.00%		100.00%
Net Asset Value Percentage	[6]	234.00%		232.00%

[1] All investments are in US Companies unless noted otherwise. Total cost, fair value, and percentage of Net Assets for the U.S. Companies were $1,181.8 million, $1,198.6 million, and 258.4%

[2] 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.

[3] 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 (See Note 6).

[4] Valued based on our accounting policy (See Note 2).

[5] Valued based on our accounting policy (See Note 2).

[6] Excludes investments in PSLF.