Geographical Information (Schedule of Revenue by Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 18,623		$ 32,591	$ 42,659	$ 62,767
United States [Member]
Segment Reporting Information [Line Items]
Revenue		$ 14,940	25,930	35,019	50,684
Asia [Member]
Segment Reporting Information [Line Items]
Revenue		2,146	4,772	4,803	8,491
Europe [Member]
Segment Reporting Information [Line Items]
Revenue		1,505	1,695	2,732	3,325
Other [Member]
Segment Reporting Information [Line Items]
Revenue		$ 32	$ 194	$ 105	$ 267