Supplemental Cash Flow Information - Supplemental Disclosure of Non-cash Activity (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Oct. 01, 2019	Sep. 30, 2019
Cash and Cash Equivalents [Line Items]
Operating lease right-of-use assets	$ 14,060			$ 0
Operating lease liabilities	16,292			0
Supplemental disclosure of cash activity:
Interest payments	60,678	$ 64,648
Income tax payments	2	568
Tax refunds received	315	12
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	152,266	68,491		106,741
Restricted cash	13,086	16,293		$ 16,053
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	165,352	$ 84,784
Accounting Standards Update 2016-02
Cash and Cash Equivalents [Line Items]
Operating lease right-of-use assets	13,895		$ 13,900
Operating lease liabilities	$ 16,028		$ 16,000