Income Taxes - Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Effective income tax rate reconciliation
Statutory federal tax rate (as a percent)	35.00%	35.00%	35.00%
Tax provision for income taxes at the statutory rate	$ (6,026)	$ 1,313	$ 16,512
Foreign tax rate differentials	(1,103)	(1,505)	(1,417)
Provision for state taxes, net of federal taxes	(371)	778	818
U.S. tax on distributed and undistributed earnings of foreign subsidiaries	452	523	419
Manufacturer's deduction		(98)	(1,213)
Tax credits	(409)	(1,198)	(240)
State tax rate change impact on deferred tax asset	192	(1,819)	1,565
Change in valuation allowance	195	408	128
Other, net	43	329	118
Total provision for (benefit from) income taxes	$ (7,027)	$ (1,269)	$ 16,690
Effective tax rate (as a percent)	40.80%	(33.80%)	35.40%