Supplemental Cash Flow Information - Supplemental Disclosure of Non-cash Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Oct. 01, 2019
Cash and Cash Equivalents [Line Items]
Operating lease right-of-use assets	$ 13,592		$ 13,103
Operating lease liabilities	15,560		15,333
Increase in operating lease right-of-use assets	1,391	$ 0
Increase in operating lease liabilities	1,391	0
Supplemental disclosure of cash activity:
Interest payments	27,048	15,954
Income tax payments	0	0
Tax refunds received	49	303
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	244,628	41,277	327,693
Restricted cash	17,420	18,759	$ 14,835
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	262,048	60,036
Accounting Standards Update 2016-02
Cash and Cash Equivalents [Line Items]
Operating lease right-of-use assets	0	13,895		$ 13,900
Operating lease liabilities	$ 0	$ 16,028		$ 16,000