CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - 3 months ended Dec. 31, 2015 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in-Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Sep. 30, 2015	$ 436,998	$ 313	$ 1,152,789	$ (2,033,644)	$ 1,368,255	$ (50,715)
Beginning Balance (in shares) at Sep. 30, 2015		31,290
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	14,700		14,700
Issuance of treasury stock under employee stock plans	(23,263)	$ 4	(37,516)	14,249
Issuance of treasury stock under employee stock plans (in shares)		401
Tax effect from share-based payment arrangements	9,615		9,615
Repurchases of common stock	(28,382)	$ (3)		(28,379)
Repurchases of common stock (shares)		(319)
Dividends paid	(622)				(622)
Net income	19,241				19,241
Foreign currency translation adjustments	(6,119)					(6,119)
Ending Balance at Dec. 31, 2015	$ 422,168	$ 314	$ 1,139,588	$ (2,047,774)	$ 1,386,874	$ (56,834)
Ending Balance (in shares) at Dec. 31, 2015		31,372