Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (32,641)	$ 36,911	$ 69,557
Other comprehensive income (loss), net of tax:
Change in unrealized gains (losses) on available-for-sale securities	23	(26)	(30)
Foreign currency translation adjustments	(10,472)	(1,406)	(809)
Other comprehensive loss, net of tax	(10,449)	(1,432)	(839)
Total comprehensive income (loss)	$ (43,090)	$ 35,479	$ 68,718