Common Stock Warrant Liability (Details) (USD $)	12 Months Ended			0 Months Ended			0 Months Ended			0 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	May 13, 2009 Five Year Warrant 1 [Member]	Dec. 31, 2012 Five Year Warrant 1 [Member]	Dec. 31, 2011 Five Year Warrant 1 [Member]	Feb. 23, 2010 Five Year Warrant 2 [Member]	Dec. 31, 2012 Five Year Warrant 2 [Member]	Dec. 31, 2011 Five Year Warrant 2 [Member]	Feb. 22, 2011 Five Year Warrant 3 [Member]	Mar. 31, 2012 Five Year Warrant 3 [Member]	Dec. 31, 2012 Five Year Warrant 3 [Member]	Dec. 31, 2011 Five Year Warrant 3 [Member]
Class of Warrant or Right [Line Items]
Exercisable period of warrants				5 years			5 years			5 years		5 years
Estimated fair value of warrants accounted for as derivative liabilities [Abstract]
Issuance Date				May 13, 2009			Feb. 23, 2010			Feb. 22, 2011
Number of Warrant Shares Issuable (in shares)	8,000,000			466,667			916,667			4,948,750		4,948,750
Exercise Price (in dollars per share)				$ 17.25			$ 12.75			$ 2.80
Warrant Expiration Date				May 13, 2014			Feb. 23, 2015			Feb. 22, 2016
Fair Value of Warrants	$ 6,305,000	$ 6,996,000		$ 3,360,000	$ 0	$ 82,000	$ 5,701,000	$ 104,000	$ 554,000	$ 8,004,000		$ 6,201,000	$ 6,360,000
Exercise of warrants by warrant holders to purchase common stock (in shares)											51,250	51,250
Proceeds from exercise of warrants	$ 6,741,000	$ 0	$ 0								$ 162,000	$ 162,000
Exercise price of warrants prior to registered public offering (in dollars per share)												$ 2.80
Exercise price of warrants post registered public offering (in dollars per share)												$ 2.80