Investments in Unconsolidated Entities - Equity and Outstanding Borrowings of Unconsolidated Entities and Equity in Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule of Equity Method Investments [Line Items]
Total equity of unconsolidated entities	$ 755,259	$ 606,062	$ 724,884	$ 593,171
Total outstanding borrowings of unconsolidated entities	1,054,938		1,054,030
Equity in income (loss) of unconsolidated entities	288	$ (75)
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities	4,590		4,464
Total equity of unconsolidated entities	7,326		7,316
Total outstanding borrowings of unconsolidated entities	$ 9,890		$ 12,708