Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Operating costs and expenses:
Operating lease expense	$ 9,046	$ 28,022
Short-term lease expense	2,747	20,297
Variable lease expense	2,354	9,161
Finance lease expense:
Amortization of ROU assets	593	1,806
Interest on lease liabilities	373	1,161
Less: sublease income	(69)	(16,794)
Total	$ 15,044	$ 43,653