CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance (in shares) at Dec. 31, 2012		80,611
Beginning Balance at Dec. 31, 2012	$ 581,317	$ 8	$ 670,732	$ 203	$ (89,626)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64,295				64,295
Net change in unrealized gain (loss) from available-for sale securities	29			29
Net change in cumulative translation adjustment	62			62
Issuance of common stock relating to employee equity compensation plans (in shares)		2,694
Issuance of common stock relating to employee equity compensation plans	34,196	$ 0	34,196
Tax withholdings related to net share settlements of restricted stock units	(4,363)		(4,363)
Common stock repurchased and retired (shares)		(2,722)
Common stock repurchased and retired	(95,107)		(24,528)		(70,579)
Excess tax benefit from share based payment arrangements	27,103		27,103
Stock based compensation	26,438		26,438
Ending Balance (in shares) at Dec. 31, 2013		80,583
Ending Balance at Dec. 31, 2013	633,970	$ 8	729,578	294	(95,910)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	145,832				145,832
Net change in unrealized gain (loss) from available-for sale securities	(238)			(238)
Net change in cumulative translation adjustment	(196)			(196)
Issuance of common stock relating to employee equity compensation plans (in shares)		1,536
Issuance of common stock relating to employee equity compensation plans	18,028	$ 0	18,028
Tax withholdings related to net share settlements of restricted stock units	(7,608)		(7,608)
Common stock repurchased and retired (shares)		(1,914)
Common stock repurchased and retired	(98,233)		(17,804)		(80,429)
Excess tax benefit from share based payment arrangements	21,393		21,393
Stock based compensation	39,823		39,823
Ending Balance (in shares) at Dec. 31, 2014		80,205
Ending Balance at Dec. 31, 2014	752,771	$ 8	783,410	(140)	(30,507)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	144,020				144,020
Net change in unrealized gain (loss) from available-for sale securities	(686)			(686)
Net change in cumulative translation adjustment	(164)		(10)	(154)
Issuance of common stock relating to employee equity compensation plans (in shares)		991
Issuance of common stock relating to employee equity compensation plans	11,325		11,325
Tax withholdings related to net share settlements of restricted stock units	(20,716)		(20,716)
Common stock repurchased and retired (shares)		(1,696)
Common stock repurchased and retired	(101,791)		(15,669)		(86,122)
Excess tax benefit from share based payment arrangements	10,224		10,224
Stock based compensation	52,943		52,943
Ending Balance (in shares) at Dec. 31, 2015		79,500
Ending Balance at Dec. 31, 2015	$ 847,926	$ 8	$ 821,507	$ (980)	$ 27,391