Nature of Business and Plan of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Net loss	$ (43,751)	$ (38,613)
Accumulated deficit	(1,227,086)		$ (1,183,335)
Total revenues	8,584	19,815
Cash and cash equivalents	$ 270,396	$ 218,383	$ 262,252	$ 267,107
Number of months Capital resources meets capital expenditures	12 months
Product
Total revenues	$ 0