Investments in Unconsolidated Entities - Unconsolidated Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities	$ 4,464	$ 4,003
Total equity of unconsolidated entities	724,884	593,171	$ 538,754	$ 644,027
Total outstanding borrowings of unconsolidated entities	12,708	8,807
Equity in income of unconsolidated entities	594	347	$ 404
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Total equity of unconsolidated entities	$ 7,316	$ 7,079