Income Taxes - Reconciliation of Effective Tax Rate to Statutory Federal Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Document Period End Date	Sep. 30, 2019
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	24.50%	35.00%
Federal tax provision (benefit) at statutory rate	$ 5,407	$ (60,647)	$ (54,138)
State tax, net of federal benefit	2,175	1,096	1,858
Foreign tax rate and other foreign related tax items	(1,341)	(10,695)	(15,768)
Stock-based compensation	3,368	3,290	6,934
Non-deductible expenditures	8,389	2,375	3,086
Change in U.S. and foreign valuation allowance	168,726	56,557	72,318
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	0	(87,058)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount	0	28,640
Executive compensation	1,662	503	5,492
Other	1,867	(1,163)	778
(Benefit) provision for income taxes	$ (88,594)	$ (62,320)	$ 23,671