Portfolio Investments - Schedule of Statement of Operations Information (Details) € in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
	Jun. 30, 2026 EUR (€)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)
Investment Company, Nonconsolidated Subsidiary [Line Items]
Total investment income | $		$ 171,740	$ 155,532	$ 536,235	$ 441,769
Credit facility interest expense | $		45,951	40,474	139,527	124,871
Total expenses | $		80,107	72,445	245,218	208,544
Net investment income | $		91,244	82,956	289,849	232,415
Realized gain (loss) | $		(10,351)	15,903	(48,813)	18,347
Net increase (decrease) in net assets resulting from operations | $		$ 83,427	$ 83,755	$ 150,380	$ 213,435
Equity investment in EDL JV
Investment Company, Nonconsolidated Subsidiary [Line Items]
Interest income	€ 28
Total investment income	28
Credit facility interest expense	9
Other expenses	107
Total expenses	116
Net investment income	(88)
Net unrealized appreciation (depreciation)	105
Realized gain (loss)	(11)
Net increase (decrease) in net assets resulting from operations	€ 6