Nature of the Business (Details Textual) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Nov. 02, 2011	Dec. 31, 2012	Dec. 31, 2011	Jan. 10, 2012 Public Offering in January 2012 [Member]	Jul. 13, 2012 Public Offering in July 2012 [Member]	Jan. 09, 2013 Public Offering Closing On January 2013 [Member]
Nature of the Business (Textual) [Abstract]
Accumulated deficit		$ (158,789,000)	$ (115,840,000)
Amount accounted for Business combination through cash and cash equivalents	50,100,000
Closure of underwritten public offering				90,000,000	115,000,000	117,500,000
Shares of common stock offered				3.6	2.8	2.5
Price per share of common stock offered				$ 25.18	$ 41.20	$ 47.53
Net proceeds from public offering				$ 84,600,000	$ 108,100,000	$ 111,100,000
Cash and cash equivalent, description		expects that it will have sufficient cash and cash equivalents to sustain operations for more than two years.
Minimum period for holding cash and cash equivalent		2 years