CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Paid-in- Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Sep. 30, 2011	$ 465,494	$ 371	$ 1,098,388	$ (1,627,180)	$ 1,015,624	$ (21,709)
Beginning Balance (in shares) at Sep. 30, 2011		37,084
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	21,229		21,229
Issuance of treasury stock under employee stock plans (in shares)		2,942
Issuance of treasury stock under employee stock plans	70,793	29	(22,085)	92,849
Tax effect from share-based payment arrangements	6,079		6,079
Repurchases of common stock (shares)		(5,187)
Repurchases of common stock	(184,291)	(52)		(184,239)
Dividends paid	(2,803)				(2,803)
Net income	92,004				92,004
Unrealized losses on investments, net of tax benefit of $3	(4)					(4)
Foreign currency translation adjustments	5,905					5,905
Ending Balance at Sep. 30, 2012	474,406	348	1,103,611	(1,718,570)	1,104,825	(15,808)
Ending Balance (in shares) at Sep. 30, 2012		34,839
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	25,850		25,850
Issuance of treasury stock under employee stock plans (in shares)		1,642
Issuance of treasury stock under employee stock plans	30,256	17	(22,150)	52,389
Tax effect from share-based payment arrangements	2,887		2,887
Repurchases of common stock (shares)		(1,695)
Repurchases of common stock	(84,893)	(17)		(84,876)
Dividends paid	(2,824)				(2,824)
Net income	90,095				90,095
Unrealized losses on investments, net of tax benefit of $3	0
Foreign currency translation adjustments	(5,100)					(5,100)
Ending Balance at Sep. 30, 2013	530,677	348	1,110,198	(1,751,057)	1,192,096	(20,908)
Ending Balance (in shares) at Sep. 30, 2013		34,786
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	36,362		36,362
Issuance of treasury stock under employee stock plans (in shares)		911
Issuance of treasury stock under employee stock plans	6,554	9	(23,278)	29,823
Tax effect from share-based payment arrangements	6,035		6,035
Repurchases of common stock (shares)		(3,650)
Repurchases of common stock	(214,898)	(37)		(214,861)
Dividends paid	(2,714)				(2,714)
Net income	94,879				94,879
Unrealized losses on investments, net of tax benefit of $3	0
Foreign currency translation adjustments	(2,281)					(2,281)
Ending Balance at Sep. 30, 2014	$ 454,614	$ 320	$ 1,129,317	$ (1,936,095)	$ 1,284,261	$ (23,189)
Ending Balance (in shares) at Sep. 30, 2014		32,047