Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interest in JV [Member]
Balance at Dec. 31, 2010	$ 357,598	$ 53		$ 596,667	$ (239,542)	$ 420
Balance, shares at Dec. 31, 2010		53,464,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchases	6,725	1		6,724
Employee stock purchase, shares	609,386	609,000
Issuance of restricted stock awards	0	0
Issuance of restricted stock awards, shares	239,576	239,000
Non-cash stock compensation	11,017			11,017
Excess tax benefit from share-based compensation arrangements	9,393			9,393
Net income	127,877				127,877
Currency translation adjustment	(968)					(968)
Unrealized gain (loss) on available for sale securities	0					0
Balance at Dec. 31, 2011	511,642	54	0	623,801	(111,665)	(548)	0
Balance, shares at Dec. 31, 2011		54,312,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchases	22,932	2		22,930
Employee stock purchase, shares	1,487,642	1,488,000
Issuance of restricted stock awards	0	0
Issuance of restricted stock awards, shares	352,391	352,000
Non-cash stock compensation	14,981			14,981
Excess tax benefit from share-based compensation arrangements	1,558			1,558
Equity component of the convertible notes, issuance, net	55,685			55,685
Purchase of convertible note hedges	(58,223)			(58,223)
Sale of warrants	38,425			38,425
Purchase of treasury stock	(50,000)		(50,000)
Purchase of treasury stock, shares			(2,193,000)
Debt issuance costs	(1,730)			(1,730)
Net income	51,170				51,254		(84)
Currency translation adjustment	(224)					(224)
Unrealized gain (loss) on available for sale securities	6					6
Balance at Dec. 31, 2012	586,222	56	50,000	697,427	(60,411)	(766)	(84)
Balance, shares at Dec. 31, 2012		56,152,000	2,193,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchases	74,213	4		74,209
Employee stock purchase, shares	3,547,431	3,547,000
Issuance of restricted stock awards	0	0
Issuance of restricted stock awards, shares	237,413	237,000
Issuance of common stock	189,599	6		189,593
Issuance of common stock, shares		6,653,000
Non-cash stock compensation	23,078			23,078
Excess tax benefit from share-based compensation arrangements	7,675			7,675
Net income	15,260				15,512		(252)
Currency translation adjustment	(3,876)					(3,876)
Unrealized gain (loss) on available for sale securities	(10)					(10)
Balance at Dec. 31, 2013	$ 892,161	$ 66	$ 50,000	$ 991,982	$ (44,899)	$ (4,652)	$ (336)
Balance, shares at Dec. 31, 2013		66,589,000	2,193,000