Organization (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (368,804,000)				$ (295,465,000)				$ (368,804,000)	$ (295,465,000)
Restricted cash	25,529,000								25,529,000
Net loss	$ (36,599,000)	$ (9,765,000)	$ (11,150,000)	$ (15,825,000)	$ (8,116.00)	$ (5,871.00)	$ (9,622.00)	$ (15,776.00)	$ (73,339,000)	$ (39,385,000)	$ (63,358,000)
Competitive therapies introduced | item									2