Income Taxes - Components of Income Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Current income tax provision (benefit):
Federal	$ 963
State	510	$ 917	$ 402
Foreign	15,860	7,608	7,499
Total current income tax provision	17,333	8,525	7,901
Deferred income tax provision (benefit):
Federal	(8,633)	(48,815)	(4,247)
State	(2,138)	(5,518)	(249)
Foreign	(6,673)	(1,443)	(25)
Total deferred income tax provision (benefit)	(17,444)	(55,776)	(4,521)
Income tax provision (benefit)	$ (111)	$ (47,251)	$ 3,380