Income Taxes - Components of Income Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Current income tax provision (benefit):
Federal			$ (145)
State	$ 917	$ 402	(193)
Foreign	7,608	7,499	4,709
Total current income tax provision	8,525	7,901	4,371
Deferred income tax provision (benefit):
Federal	(48,815)	(4,247)	59,906
State	(5,518)	(249)	4,000
Foreign	(1,443)	(25)	(2,027)
Total deferred income tax provision (benefit)	(55,776)	(4,521)	61,879
Income tax provision (benefit)	$ (47,251)	$ 3,380	$ 66,250