Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenues (Note 1(b))	$ 0	$ 0	$ 0	$ 0
Operating costs and expenses:
Selling, general and administrative	14,744	17,230	29,538	33,182
Research and development	21,746	16,982	37,739	38,868
Total operating costs and expenses	36,490	34,212	67,277	72,050
Loss from continuing operations before other expense and income taxes	(36,490)	(34,212)	(67,277)	(72,050)
Other income (expense):
Interest income, net	325	1,495	1,029	2,556
Other income (expense), net	3,945	3,722	(6,589)	(7,563)
Total other income (expense)	4,270	5,217	(5,560)	(5,007)
Loss from continuing operations before income taxes	(32,220)	(28,995)	(72,837)	(77,057)
(Provision) benefit for income taxes from continuing operations	(9)	212	(9)	8,428
Loss from continuing operations	(32,229)	(28,783)	(72,846)	(68,629)
Income from discontinued operations, net of income taxes (Note 10)	144	388	189	20,975
Net loss	$ (32,085)	$ (28,395)	$ (72,657)	$ (47,654)
Basic and diluted loss per share:
Loss per common share from continuing operations ($ per share)	$ (0.29)	$ (0.26)	$ (0.65)	$ (0.63)
Income per common share from discontinued operations ($ per share)	0.00	0.00	0.00	0.19
Net loss per common share ($ per share)	$ (0.28)	$ (0.26)	$ (0.65)	$ (0.43)
Weighted average shares outstanding, basic and diluted	112,615,744	110,345,135	112,199,229	109,744,405