Nature of Business and Plan of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Net loss	$ (29,088)	$ (43,751)
Accumulated deficit	(1,316,556)		$ (1,287,468)
Total revenues	13,287	8,584
Cash and cash equivalents	247,299	$ 270,396	$ 176,225	$ 262,252
Net proceeds generated from public offering	$ 97,744
Number of months Capital resources meets capital expenditures	12 months
Product
Total revenues	$ 0