Common Stock Warrant Liability (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended			0 Months Ended			0 Months Ended			0 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	May 13, 2009 Five Year Warrant 1 [Member]	Jun. 30, 2014 Five Year Warrant 1 [Member]	Dec. 31, 2013 Five Year Warrant 1 [Member]	Feb. 23, 2010 Five Year Warrant 2 [Member]	Jun. 30, 2014 Five Year Warrant 2 [Member]	Dec. 31, 2013 Five Year Warrant 2 [Member]	Feb. 22, 2011 Five Year Warrant 3 [Member]	Jun. 30, 2014 Five Year Warrant 3 [Member]	Jun. 30, 2014 Five Year Warrant 3 [Member]	Jun. 30, 2013 Five Year Warrant 3 [Member]	Dec. 31, 2013 Five Year Warrant 3 [Member]
Class of Warrant or Right [Line Items]
Exercisable period of warrants				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)				466,667			916,669			4,552,600	4,600,000	4,600,000
Exercise Price (in dollars per share)				$ 17.25			$ 12.75			$ 1.50	$ 1.50	$ 1.50
Warrant Expiration Date				May 13, 2014			Feb. 23, 2015			Feb. 22, 2016
Fair Value of Warrants	$ 3,224		$ 5,425	$ 3,360	$ 0	$ 0	$ 5,701	$ 0	$ 6	$ 8,004	$ 3,224	$ 3,224		$ 5,419
Exercise of warrants by warrant holders to purchase common stock (in shares)											0	282,350	0
Proceeds from exercise of warrants	$ 423	$ 0										$ 400