CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury stock
Balance at Dec. 31, 2010	$ 828,398	$ 988	$ 186,546	$ 882,425	$ 281	$ (241,842)
Balance (in shares) at Dec. 31, 2010		197,462				(19,502)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	18,619		18,619
Exercise of stock options	20,318	6	20,312
Exercise of stock options (in shares)		1,181
Issuance of restricted stock (in shares)		86
Excess tax benefits from share based payment arrangements	3,824		3,824
Repurchase of common stock	(176,392)					(176,392)
Repurchase of common stock (in shares)						(4,950)
Foreign currency translation	(3,306)				(3,306)
Change in unrealized gain on available-for-sale securities, net of tax	1,478				1,478
Net income	286,219			286,219
Balance at Dec. 31, 2011	979,158	994	229,301	1,168,644	(1,547)	(418,234)
Balance (in shares) at Dec. 31, 2011		198,729				(24,452)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation	28,007		28,007
Exercise of stock options	11,014	25	10,989
Exercise of stock options (in shares)		5,030
Excess tax benefits from share based payment arrangements	19,656		19,656
Repurchase of common stock	(737,079)					(737,079)
Repurchase of common stock (in shares)						(13,531)
Foreign currency translation	2,096				2,096
Change in unrealized gain on available-for-sale securities, net of tax	1,525				1,525
Net income	340,020			340,020
Balance at Dec. 31, 2012	644,397	1,019	287,953	1,508,664	2,074	(1,155,313)
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	21,251	11	21,240
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	$ 992,279	$ 1,030	$ 368,069	$ 1,847,325	$ (1,233)	$ (1,222,912)
Balance (in shares) at Dec. 31, 2013		206,014				(39,192)