CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2009	$ 273,036	$ 7	$ 525,073	$ 455	$ (252,499)
Beginning Balance (in shares) at Dec. 31, 2009		74,568
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	74,253				74,253
Net change in unrealized gain (loss) from available-for sale securities	(19)			(19)
Net change in cumulative translation adjustment	(302)			(302)
Comprehensive income (loss)	73,932
Issuance of common stock relating to employee equity compensation plans (in shares)		1,822
Issuance of common stock relating to employee equity compensation plans	11,822	1	11,821
Tax withholdings related to net share settlements of restricted stock units	(1,080)		(1,080)
Excess tax benefit from share based payment arrangements	3,965		3,965
Stock based compensation	16,072		16,072
Ending Balance at Dec. 31, 2010	377,747	8	555,851	134	(178,246)
Ending Balance (in shares) at Dec. 31, 2010		76,390
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	66,716				66,716
Net change in unrealized gain (loss) from available-for sale securities	10			10
Net change in cumulative translation adjustment	(98)			(98)
Comprehensive income (loss)	66,628
Issuance of common stock relating to employee equity compensation plans (in shares)		2,708
Issuance of common stock relating to employee equity compensation plans	25,501	0	25,501
Tax withholdings related to net share settlements of restricted stock units	(1,897)		(1,897)
Common stock repurchased and retired (shares)		322
Common stock repurchased and retired	7,754		2,771		4,983
Excess tax benefit from share based payment arrangements	11,391		11,391
Stock based compensation	19,165		19,165
Ending Balance at Dec. 31, 2011	490,781	8	607,240	46	(116,513)
Ending Balance (in shares) at Dec. 31, 2011		78,776
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58,691				58,691
Net change in unrealized gain (loss) from available-for sale securities	28			28
Net change in cumulative translation adjustment	129			129
Comprehensive income (loss)	58,848
Issuance of common stock relating to employee equity compensation plans (in shares)		3,565
Issuance of common stock relating to employee equity compensation plans	42,327		42,327
Tax withholdings related to net share settlements of restricted stock units	(2,106)		(2,106)
Common stock repurchased and retired (shares)		1,730
Common stock repurchased and retired	47,203		15,399		31,804
Excess tax benefit from share based payment arrangements	17,187		17,187
Stock based compensation	21,483		21,483
Ending Balance at Dec. 31, 2012	$ 581,317	$ 8	$ 670,732	$ 203	$ (89,626)
Ending Balance (in shares) at Dec. 31, 2012		80,611