Significant Accounting Policies and Recent Accounting Updates (Details) - USD ($)		3 Months Ended		9 Months Ended
	Oct. 06, 2023	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023	Aug. 31, 2023	Aug. 03, 2023
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest income, operating, accretion of discounts		$ 6,632,000	$ 4,660,000	$ 16,489,000	$ 15,351,000
Amortization of deferred loan origination fees, net		6,300,000	2,663,000	10,298,000	14,049,000
Payment-in-kind interest income		10,177,000	9,587,000	33,805,000	27,270,000
Payment-in-kind interest capitalized		11,245,000	10,405,000	36,551,000	27,660,000
Investment company, premium prepayment fees		162,000	0	338,000	79,000
Interest and fee income		132,038,000	139,293,000	417,195,000	380,046,000
Dividend income, operating, paid in kind		5,287,000	3,723,000	13,890,000	10,767,000
Non-cash dividend income		5,287,000	3,723,000	13,890,000	10,767,000
Proceeds from dividends received		47,000	0	47,000	0
Fair value non-accrual loan		70,292,000		70,292,000		$ 62,937,000
Amortization of debt premium		3,086,000	1,570,000	5,493,000	5,357,000
Excise tax		125,000	0	1,124,000	2,432,000
Income tax		0	0	71,000	0
Stock repurchase program, authorized amount							$ 150,000,000	$ 150,000,000
Offering costs, partnership interests	$ 250,000,000
Maximum percentage of gross sales, commission received, percentage	1.50%
Deferred debt issuance cost		22,232,000		22,232,000		$ 15,613,000
Amortization of deferred debt issuance costs		2,214,000	1,937,000	6,869,000	5,362,000
Non-Senior Loan Fund
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Dividend income		418,000	334,000	555,000	1,329,000
Return of capital		$ 733,000	$ 212,000	$ 1,551,000	$ 295,000