Income Taxes - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income (loss) before income taxes:
U.S.	$ (25,090)	$ (4,160)	$ 36,327
Foreign	7,873	7,911	10,849
Income (loss) before income taxes	(17,217)	3,751	47,176
Current:
U.S. Federal	933	(4,427)	11,207
Foreign	1,652	1,368	1,690
State	401	(141)	686
Total	2,986	(3,200)	13,583
Deferred:
U.S. Federal	(8,781)	4,582	(79)
Foreign		(105)	690
State	(1,427)	(2,954)	2,368
Valuation allowance	195	408	128
Total	(10,013)	1,931	3,107
Total provision for (benefit from) income taxes	$ (7,027)	$ (1,269)	$ 16,690