Supplemental Cash Flow Information - Supplemental Disclosure of Non-cash Activity (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Supplemental Cash Flow Elements [Abstract]
Increase in operating lease right-of-use assets	$ 626	$ 1,453
Increase in operating lease liabilities	626	1,453
Supplemental disclosure of cash activity:
Interest payments	34,649	37,412
Income tax payments	2,578	143
Tax refunds received	0	49
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	163,905	355,533	$ 246,715
Restricted cash	33,343	18,162	$ 27,428
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 197,248	$ 373,695