Stockholders' Equity (Details) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended				0 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Apr. 08, 2009	Oct. 30, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Feb. 28, 2011	Apr. 08, 2009 Common Stock [Member]	Dec. 31, 2010 Warrants [Member]	Oct. 30, 2009 Common Stock [Member]	Dec. 31, 2011 Common Stock [Member]	Dec. 31, 2010 Common Stock [Member]	Dec. 31, 2009 Common Stock [Member]	Feb. 28, 2011 4.75% Convertible Senior Notes Due On 2018 [Member]	Dec. 31, 2011 4.75% Convertible Senior Notes Due On 2018 [Member]
Stockholders' Equity [Line Items]
Principal amount			$ 1,000										$ 230,000,000	$ 230,000,000
Convertible senior notes, maturity date			Feb. 01, 2018										Feb. 01, 2018	Feb. 01, 2018
Conversion feature of Convertible Notes													35,600,000
Deferred tax liability set-up related to the Convertible Notes (net of finance costs)						22,700,000
Net increase in the valuation of the warrants				16,800,000
Issuance costs							2,000,000						1,900,000
Registered direct offering common stock, raised			632,000	326,000	353,000		31,000,000			1,000		1,000
Registered direct offering common stock yield for cash					61,366,000		29,000,000		61,400,000
Common stock, shares issued			71,502,000	70,259,000			5,927,343	2,227,963
Shares purchasable with issued warrants	5,038,237
Initial exercise price of warrants, per share	$ 10.46
Initial exercise price of warrants	$ 10.46
Fair value of warrant liabilities	12,600,000
Proceeds from warrant exercises								8,500,000
Warrant exercised to purchase common stock, shares				5,038,237				812,617
Warrants to purchase common stock on cashless settlement process								4,225,620
Common stock were exercised, resulting in forfeiture								1,997,657
Proceeds from underwritten public offering, shares		4,945,000								155,000	30,000	81,000
Proceeds from issuance of common stock for cash on underwritten public offering, net of expenses					$ 61,366,000		$ 29,000,000		$ 61,400,000