CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,503)	$ (10,965)	$ (23,208)	$ (22,007)
Other comprehensive loss
Change in unrealized gains (losses) on available-for-sale securities, net of tax	11	31	(51)	5
Foreign currency translation adjustments	1,353	(366)	1,047	(1,588)
Total other comprehensive income (loss)	1,364	(335)	996	(1,583)
Total comprehensive loss	$ (10,139)	$ (11,300)	$ (22,212)	$ (23,590)