Supplemental Cash Flow Information - Supplemental Disclosure of Non-cash Activity (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Supplemental disclosure of cash activity:
Interest payments	$ 48,277	$ 43,433
Income tax payments	61	10
Tax refunds received	12	39
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	86,441	158,787	$ 139,805
Restricted cash	12,197	12,783	$ 13,443
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 98,638	$ 171,570