Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 36,911	$ 69,557	$ 35,118
Other comprehensive income (loss):
Change in unrealized gains (losses) on available-for-sale securities (net of tax)	(26)	(11)	41
Reclassification adjustment (gains) losses included in net income (net of tax)		(19)	1
Unrealized gains (losses) on available- for-sale securities (net of tax)	(26)	(30)	42
Foreign currency translation adjustments	(1,406)	(809)	(437)
Other comprehensive loss	(1,432)	(839)	(395)
Total comprehensive income	$ 35,479	$ 68,718	$ 34,723