Warrants to Purchase Preferred Stock and Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended																	0 Months Ended	9 Months Ended
	Jul. 02, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jul. 25, 2013 Warrants expiring February 8, 2020	Jul. 25, 2013 Warrants expiring December 7, 2018	Jul. 25, 2013 Warrants expiring June 7, 2017	Sep. 30, 2013 Preferred stock	Dec. 31, 2012 Preferred stock	Sep. 30, 2013 Preferred stock Series A	Dec. 31, 2012 Preferred stock Series A	Sep. 30, 2013 Preferred stock Series B-1	Dec. 31, 2012 Preferred stock Series B-1	Sep. 30, 2013 Preferred stock Series C	Dec. 31, 2012 Preferred stock Series C	Sep. 30, 2013 Preferred stock Series 1	Dec. 31, 2012 Preferred stock Series 1	Sep. 30, 2013 Preferred stock Series 3	Dec. 31, 2012 Preferred stock Series 3	Jul. 25, 2013 Common stock	Sep. 30, 2013 Common stock		Jul. 25, 2013 Common stock Warrants expiring February 8, 2020	Jul. 25, 2013 Common stock Warrants expiring December 7, 2018	Jul. 25, 2013 Common stock Warrants expiring June 7, 2017	Sep. 30, 2013 Common stock Warrants expiring June 30, 2017	Sep. 30, 2013 Common stock Warrants expiring February 6, 2015
Warrants to purchase preferred stock and common stock
Exercise Price (in dollars per share)						$ 3.79	$ 4.64	$ 1.27			$ 1.27		$ 4.86		$ 3.79		$ 2.46		$ 5.75								$ 2.46	$ 5.75
Warrants Outstanding (in shares)									140,933		35,520		33,930		31,659		31,130		8,694			39,824					31,130	8,694
Fair Value										$ 1,103		$ 299		$ 246		$ 245		$ 256		$ 57
Mark-to-market income related to the fair value measurement of the warrants		$ 136	$ 5	$ 313	$ 19
Number of warrants to purchase common stock, issued on conversion of warrants to purchase mandatorily redeemable convertible preferred stock	142,534
Number of shares of common stock issued on exercise of warrants																								17,607	16,210	30,250
Common stock issued on exercise of warrants																					64,067	64,067	[1],[2],[3]
Number of shares of common stock tendered to the Company																								14,052	19,321	5,270

[1] All share amounts have been restated to reflect a 1-for-1.5 reverse stock split, refer to note 10.

[2] The Common Stock, as of December 31, 2012, included two series of Common Stock, refer to note 10.

[3] All share amounts have been restated to reflect the renaming of the Company's "Series I common stock" to "common stock", refer to note 10.