Consolidated Statements of Stockholders' Equity (Net Capital Deficiency) (USD $) In Thousands, except Share data, unless otherwise specified	Total USD ($)	Common Stock	Common Stock USD ($)	Common Stock Class A Common Stock USD ($)	Additional Paid-In Capital USD ($)	Accumulated Other Comprehensive Income USD ($)	Accumulated Deficit USD ($)
Balance at Dec. 31, 2009	$ (188,994)		$ 549	$ 94	$ 927,082	$ 35	$ (1,116,754)
Balance (in shares) at Dec. 31, 2009			54,830,000	9,402,000
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, and issuance of common stock in settlement of restricted stock units, stock awards and purchase plan	8,761		17		8,744
Exercise of stock options, and issuance of common stock in settlement of restricted stock units, stock awards and purchase plan (in shares)			1,745,000
Issuance of common stock for cash in secondary stock offering, net of expenses of $5.7 million	93,478		86		93,392
Issuance of common stock for cash in secondary stock offering, expenses (in shares)			8,625,000
Issuance of common stock in private placement to a related party, net of expenses of $0.4 and $0.2 million for the year ended 2012 and 2010, respectively	129,190		58		129,132
Issuance of common stock in private placement to a related party, expenses (in shares)			5,750,000
Stock-based compensation	19,009				19,009
Net loss	(83,862)						(83,862)
Net unrealized gain (loss) on marketable securities	(2)					(2)
Balance at Dec. 31, 2010	(22,420)		710	94	1,177,359	33	(1,200,616)
Balance (in shares) at Dec. 31, 2010			70,950,000	9,402,000
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, and issuance of common stock in settlement of restricted stock units, stock awards and purchase plan	12,195		46		12,149
Exercise of stock options, and issuance of common stock in settlement of restricted stock units, stock awards and purchase plan (in shares)			4,617,000
Issuance of common stock in private placement to a related party, net of expenses of $0.4 and $0.2 million for the year ended 2012 and 2010, respectively	13,618		5		13,613
Issuance of common stock in private placement to a related party, expenses (in shares)			574,000
Conversion of Class A common stock (Note 3)			94	(94)
Conversion of Class A common stock (Note 3) (in shares)			9,402,000	(9,402,000)
Stock-based compensation	24,916				24,916
Net loss	(115,344)						(115,344)
Net unrealized gain (loss) on marketable securities	(17)					(17)
Balance at Dec. 31, 2011	(87,052)		855		1,228,037	16	(1,315,960)
Balance (in shares) at Dec. 31, 2011		85,543,000	85,543,000
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, and issuance of common stock in settlement of restricted stock units, stock awards and purchase plan	7,081		22		7,059
Exercise of stock options, and issuance of common stock in settlement of restricted stock units, stock awards and purchase plan (in shares)			2,151,000
Issuance of common stock in private placement to a related party, net of expenses of $0.4 and $0.2 million for the year ended 2012 and 2010, respectively	229,296		107		229,189
Issuance of common stock in private placement to a related party, expenses (in shares)			10,685,000
Stock-based compensation	24,162				24,162
Net loss	(18,542)						(18,542)
Net unrealized gain (loss) on marketable securities	83					83
Balance at Dec. 31, 2012	$ 155,028		$ 984		$ 1,488,447	$ 99	$ (1,334,502)
Balance (in shares) at Dec. 31, 2012		98,379,000	98,379,000