Nature of Business and Plan of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Nature of Business and Plan of Operations
Net loss	$ (8,867)	$ (45,922)	$ (26,212)	$ (77,850)
Accumulated deficit	(958,782)		(958,782)		$ (932,570)
Product revenue			0
Cash and cash equivalents	$ 150,337	$ 245,026	$ 150,337	$ 245,026	$ 159,964	$ 212,283