CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury stock.	Total
Balance at Dec. 31, 2012	$ 1,019	$ 287,953	$ 1,508,664	$ 2,074	$ (1,155,313)	$ 644,397
Balance (in shares) at Dec. 31, 2012	203,759				(37,983)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation		28,528				28,528
Exercise of stock options	$ 11	21,240				21,251
Exercise of stock options (in shares)	2,255
Excess tax benefits from share based payment arrangements		30,348				30,348
Repurchase of common stock					$ (67,599)	(67,599)
Repurchase of common stock (in shares)					(1,209)
Foreign currency translation				(1,782)		(1,782)
Reclassification adjustment for net gains included in net income				(1,525)		(1,525)
Net income			338,661			338,661
Balance at Dec. 31, 2013	$ 1,030	368,069	1,847,325	(1,233)	$ (1,222,912)	992,279
Balance (in shares) at Dec. 31, 2013	206,014				(39,192)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation		28,989				28,989
Exercise of stock options	$ 5	17,163				17,168
Exercise of stock options (in shares)	990
Excess tax benefits from share based payment arrangements		11,924				11,924
Repurchase of common stock					$ (8,175)	(8,175)
Repurchase of common stock (in shares)					(90)
Foreign currency translation				(10,220)		(10,220)
Net income			483,185			483,185
Balance at Dec. 31, 2014	$ 1,035	426,145	2,330,510	(11,453)	$ (1,231,087)	1,515,150
Balance (in shares) at Dec. 31, 2014	207,004				(39,282)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation		32,719				32,719
Exercise of stock options	$ 37	49,291				49,328
Exercise of stock options (in shares)	7,425
Issuance of Common Stock	$ 170	3,168,965				3,169,135
Issuance of common stock (in shares)	34,041
Excess tax benefits from share based payment arrangements		314,737				314,737
Repurchase of common stock					$ (807,967)	$ (807,967)
Repurchase of common stock (in shares)					(6,288)
Cancellation of treasury stock	$ (207)		(1,482,380)		$ 1,482,587
Cancellation of treasury stock (in shares)	(41,451)				41,451	(41,500)
Foreign currency translation				(10,425)		$ (10,425)
Net income			546,733			546,733
Balance at Dec. 31, 2015	$ 1,035	$ 3,991,857	$ 1,394,863	$ (21,878)	$ (556,467)	$ 4,809,410
Balance (in shares) at Dec. 31, 2015	207,019				(4,119)