Leases - Lessee Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019
Leases [Abstract]
Right-of-use asset	$ 170,479	$ 183,809	$ 206,839	$ 183,809
Lease liability, current	41,060	49,742	44,076	49,742
Lease liability, non-current	138,622	153,040	171,006	$ 153,040
Present value of operating lease liabilities	$ 179,682	$ 202,782	$ 215,082