Common stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		9 Months Ended			0 Months Ended	1 Months Ended		12 Months Ended		1 Months Ended		1 Months Ended
	Aug. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Aug. 13, 2012 item	Sep. 13, 2012 Issuance under private placement	Aug. 31, 2012 Issuance under private placement	Aug. 13, 2012 Issuance under private placement	Dec. 31, 2012 Series A Preferred Stock	Jul. 31, 2011 Series A Preferred Stock	Aug. 31, 2012 Series A Preferred Stock Issuance under private placement	Mar. 29, 2012 Series B Preferred Stock	Aug. 31, 2012 Series B Preferred Stock Issuance under private placement
Common stock
Reverse stock split conversion ratio		2.023
Common stock
Number of common stock issued (in shares)							897,554
Common stock issue price (in dollars per share)								$ 5.50		$ 1.00		$ 5.50
Aggregate purchase price			$ 1				$ 4,039
Preferred stock conversion ratio									2.023		2.023
Number of shares of common stock in which preferred stock is convertible							897,554				3,064,753		6,770,563
Number of classes of board of directors					3
Staggered term of board of directors	3 years
Percentage of the shares of capital stock, whose holders' affirmative vote is required to remove directors	75.00%
Number of common shares to be included in the Resale S-1						7,630,683	897,554						6,770,563
Outstanding stock options (in shares)			617,633	1,218,153
Outstanding restricted stock units				192,308