Geographical Information (Schedule of Revenue by Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenue	$ 25,241	$ 17,717	$ 18,623	$ 24,036	$ 29,176	$ 30,952	$ 32,591	$ 30,176	$ 85,617	$ 122,895	$ 91,998
United States
Segment Reporting Information [Line Items]
Revenue									69,543	98,520	66,436
Asia
Segment Reporting Information [Line Items]
Revenue									10,386	16,713	17,401
Europe
Segment Reporting Information [Line Items]
Revenue									5,422	7,015	7,618
Other
Segment Reporting Information [Line Items]
Revenue									$ 266	$ 647	$ 543