Revenue Recognition - Other Management Agreements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Managed Operating Companies
Related Party Transaction [Line Items]
Business management fee percent based on management agreements			0.60%
Aggregate business management fees	$ 6,460	$ 5,374	$ 13,030	$ 11,012
ABP Trust, AIC, The Industrial Fund and The Open End Fund
Related Party Transaction [Line Items]
Aggregate business management fees	$ 2,758	$ 1,271	$ 4,159	$ 2,187