Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (45,970)	$ (32,641)	$ 36,911
Other comprehensive income (loss), net of tax:
Change in unrealized gains (losses) on available-for-sale securities	(12)	23	(26)
Foreign currency translation adjustments	(2,984)	(10,472)	(1,406)
Other comprehensive loss, net of tax	(2,996)	(10,449)	(1,432)
Total comprehensive income (loss)	$ (48,966)	$ (43,090)	$ 35,479