Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue:
Revenue	$ 3,878	$ 2,765	$ 7,067	$ 5,112
Operating expenses:
Research and development	9,347	11,292	17,457	21,297
General and administrative	7,569	6,333	14,266	12,028
Change in contingent consideration liability	1,300	700	2,100	2,600
Total operating expenses	18,216	18,325	33,823	35,925
Operating loss	(14,338)	(15,560)	(26,756)	(30,813)
Other (expense) income:
Interest (expense) income, net	(930)	(1,076)	(1,936)	(2,183)
Total other (expense) income	(930)	(1,076)	(1,936)	(2,183)
Loss before income tax benefit	(15,268)	(16,636)	(28,692)	(32,996)
Income tax benefit	96		96
Net loss	$ (15,172)	$ (16,636)	$ (28,596)	$ (32,996)
Net loss per share - basic and diluted (in dollars per share)	$ (0.20)	$ (0.24)	$ (0.39)	$ (0.47)
Weighted-average shares - basic and diluted (in shares)	74,017	70,202	73,271	70,214
Royalty [Member]
Revenue:
Revenue	$ 3,530	$ 2,601	$ 6,588	$ 4,720
License [Member]
Revenue:
Revenue	333	147	463	362
Product and Service, Other [Member]
Revenue:
Revenue	$ 15	$ 17	$ 16	$ 30