Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Operating activities:
Net increase (decrease) in net assets resulting from operations	$ 33,920	$ 57,905	$ 117,331
Adjustments to reconcile net increase (decrease) in net assets resulting from operations to net cash provided by (used in) operating activities:
Net unrealized (appreciation) depreciation	101,229	(19,101)	28,555
Net realized (gains) losses	17,097	136,356	33,155
PIK interest income	(19,423)	(20,832)	(19,764)
Accretion of original issue discount on investments	(17,990)	(17,991)	(22,314)
Accretion of original issue discount on unsecured notes payable	1,004	1,304	783
Amortization of deferred financing costs	8,797	5,036	4,599
Deferred taxes	269	(5)	1,670
Purchases of investments	(958,743)	(1,281,419)	(742,144)
Proceeds from the sales and repayments of investments	1,044,719	1,086,222	911,975
Cash received in the OSI2 Merger	0	0	22,317
Changes in operating assets and liabilities:
(Increase) decrease in interest, dividends and fees receivable	7,055	1,641	578
(Increase) decrease in due from portfolio companies	9,344	(6,213)	16,283
(Increase) decrease in receivables from unsettled transactions	12,599	37,893	(50,742)
(Increase) decrease in due from broker	1,510	37,200	(8,730)
(Increase) decrease in other assets	(720)	906	14
Increase (decrease) in accounts payable, accrued expenses and other liabilities	(1,954)	(458)	(53,118)
Increase (decrease) in base management fee and incentive fee payable	(3,002)	(4,030)	(489)
Increase (decrease) in due to affiliate	(2,519)	(222)	408
Increase (decrease) in interest payable	(4,164)	224	4,379
Increase (decrease) in payables from unsettled transactions	(655)	4,660	(15,975)
Increase (decrease) in director fees payable	0	0	(9)
Net cash provided by (used in) operating activities	228,373	19,076	228,762
Financing activities:
Distributions paid in cash	(148,199)	(176,814)	(180,046)
Borrowings under credit facilities	500,000	255,000	572,000
Repayments of borrowings under credit facilities	(665,000)	(255,000)	(787,000)
Repayments of unsecured notes	(300,000)	0	0
Issuance of unsecured notes	299,976	0	296,511
Shares issued under the "at the market" offering	2,960	92,748	1,370
Repurchases of common stock under dividend reinvestment plan	(10,666)	(1,551)	(2,418)
Shares issued in private placement	100,000	0	0
Deferred financing costs paid	(8,377)	(1,039)	(10,596)
Deferred offering costs paid	(43)	(117)	(235)
Net cash provided by (used in) financing activities	(229,349)	(86,773)	(110,414)
Effect of exchange rate changes on foreign currency	2,063	701	827
Net increase (decrease) in cash and cash equivalents and restricted cash	1,087	(66,996)	119,175
Cash and cash equivalents and restricted cash, beginning of period	78,543	145,539	26,364
Cash and cash equivalents and restricted cash, end of period	79,630	78,543	145,539
Supplemental information:
Cash paid for interest	110,208	122,058	98,189
Non-cash financing activities:
Issuance of shares of common stock under dividend reinvestment plan	0	5,662	3,436
Deferred financing costs	0	1,000	442
Deferred offering costs	0	0	12
Issuance of shares in connection with the OSI2 Merger	0	0	334,034
Reconciliation to the Consolidated Statements of Assets and Liabilities
Cash and cash equivalents	79,630	63,966	136,450
Restricted cash	0	14,577	9,089
Total cash and cash equivalents and restricted cash	$ 79,630	$ 78,543	$ 145,539