Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (56,791)	$ (45,970)	$ (32,641)
Other comprehensive income (loss), net of tax:
Change in unrealized gains (losses) on available-for-sale securities	(43)	(12)	23
Foreign currency translation adjustments	1,754	(2,984)	(10,472)
Other comprehensive income (loss), net of tax	1,711	(2,996)	(10,449)
Total comprehensive loss	$ (55,080)	$ (48,966)	$ (43,090)