Nature of Business and Plan of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Nature of Business and Plan of Operations
Net loss	$ (17,345)	$ (31,928)
Accumulated deficit	(949,915)		$ (932,570)
Product revenue	0
Cash and cash equivalents	$ 126,568	$ 182,913	$ 159,964	$ 212,283