Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Supplemental disclosure of non-cash activity:
Increase in operating leases right-of-use assets		$ 10,829	$ 835	$ 2,905
Increase in operating leases liabilities		11,276	835	2,905
Derecognition of investment in unconsolidated entities		0	3,641	0
Supplemental disclosure of cash activity:
Interest payments		67,342	70,132	74,171
Income tax payments		1,956	4,216	3,462
Tax refunds received	$ 9,200	9,987	0	1,078
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents		345,590	214,594	246,715
Restricted cash		40,699	37,234	27,428
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows		$ 386,289	$ 251,828	$ 274,143	$ 342,528