CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Class A Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2009	$ 396,762	$ 2	$ 79	$ 1,336,732	$ (941,095)	$ 1,044
Balance (shares) at Dec. 31, 2009		2,245,000	78,861,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in a public offering, net of issuance costs	174,828		6	174,822
Issuance of Common Stock in a public offering, net of issuance costs (in shares)			6,325,000
Issuance of Common Stock in connection with exercise of stock options	25,262		2	25,260
Issuance of Common Stock in connection with exercise of stock options (shares)			1,575,000
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (shares)			(42,000)
Common stock tendered upon exercise of stock options in connection with employee tax obligations	(3,798)			(3,798)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	2,867			2,867
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)			111,000
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)			345,000
Conversion of Class A Stock to Common Stock (shares)		(63,000)	63,000
Stock-based compensation charges	39,897			39,897
Net income (loss)	(104,468)				(104,468)
Other comprehensive income (loss), net of tax	(3,535)					(3,535)
Balance at Dec. 31, 2010	527,815	2	87	1,575,780	(1,045,563)	(2,491)
Balance (shares) at Dec. 31, 2010		2,182,000	87,238,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	43,615		4	43,611
Issuance of Common Stock in connection with exercise of stock options (shares)			3,770,000
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (shares)			(446,000)
Common stock tendered upon exercise of stock options in connection with employee tax obligations	(22,440)			(22,440)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	6,979			6,979
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)			92,000
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)			16,000
Restricted Common Stock tendered upon vesting in connection with employee tax obligations	(2,638)			(2,638)
Restricted Common Stock tendered upon vesting in connection with employee tax obligations (shares)			(51,000)
Conversion of Class A Stock to Common Stock (shares)		(73,000)	73,000
Stock-based compensation charges	56,609			56,609
Equity component of convertible senior notes, net of issuance costs	120,623			120,623
Purchase of convertible note hedges	(117,500)			(117,500)
Issuance of warrants in connection with issuance of convertible senior notes	93,800			93,800
Net income (loss)	(221,760)				(221,760)
Other comprehensive income (loss), net of tax	629					629
Balance at Dec. 31, 2011	485,732	2	91	1,754,824	(1,267,323)	(1,862)
Balance (shares) at Dec. 31, 2011		2,109,000	90,692,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock in connection with exercise of stock options	67,174		5	67,169
Issuance of Common Stock in connection with exercise of stock options (shares)			5,086,000
Common Stock tendered upon exercise of stock options in connection with employee tax obligations (shares)			(878,000)
Common stock tendered upon exercise of stock options in connection with employee tax obligations	(112,834)		(1)	(112,833)
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution	6,325			6,325
Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (shares)			64,000
Issuance of restricted Common Stock under Long-Term Incentive Plan (shares)			501,000
Restricted Common Stock tendered upon vesting in connection with employee tax obligations	(50,466)			(50,466)
Restricted Common Stock tendered upon vesting in connection with employee tax obligations (shares)			(282,000)
Conversion of Class A Stock to Common Stock (shares)		(40,000)	40,000
Stock-based compensation charges	94,181			94,181
Excess tax benefit from stock-based compensation				4,308
Net income (loss)	750,269				750,269
Other comprehensive income (loss), net of tax	696					696
Balance at Dec. 31, 2012	$ 1,245,385	$ 2	$ 95	$ 1,763,508	$ (517,054)	$ (1,166)
Balance (shares) at Dec. 31, 2012		2,069,000	95,223,000