Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss), Net	Accumulated Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2011	$ 181,784	$ 78	$ 646,815	$ 5,793	$ 742,579	$ (1,213,481)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	165,903				165,903
Other comprehensive income (loss)	175			175
Issuances under stock plans	12,433		(24,626)			37,059
Stock compensation tax benefits	21,304		21,304
Common share repurchases	(111,304)					(111,304)
Stock compensation expense			36,378
Ending Balance at Dec. 31, 2012	306,673	78	679,871	5,968	908,482	(1,287,726)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	182,801				182,801
Other comprehensive income (loss)	2,377			2,377
Issuances under stock plans	6,034		(21,354)			27,388
Stock compensation tax benefits	25,392		25,392
Common share repurchases	(196,696)					(196,696)
Stock compensation expense	34,735		34,735
Ending Balance at Dec. 31, 2013	361,316	78	718,644	8,345	1,091,283	(1,457,034)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	183,766				183,766
Other comprehensive income (loss)	(29,515)			(29,515)
Issuances under stock plans	7,800		(11,727)			19,527
Stock compensation tax benefits	18,671		18,671
Common share repurchases	(419,712)					(419,712)
Stock compensation expense	38,845		38,845
Ending Balance at Dec. 31, 2014	$ 161,171	$ 78	$ 764,433	$ (21,170)	$ 1,275,049	$ (1,857,219)