STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUES:
Product Development and Licensing Agreements	$ 3,153	$ 2,174	$ 1,442
Contracts and Grants	9,590	4,612	4,038
Total Revenues	12,743	6,786	5,480
OPERATING EXPENSES:
Research and Development	96,171	102,726	100,171
General and Administrative	25,003	35,979	33,837
In-Process Research and Development Impairment	13,000
Gain on Fair Value Remeasurement of Contingent Consideration	(800)
Amortization of Acquired Intangible Assets	896	997	1,013
Total Operating Expenses	134,270	139,702	135,021
Operating Loss	(121,527)	(132,916)	(129,541)
Investment and Other Income, Net	4,214	4,386	2,344
Net Loss Before Income Tax Benefit	(117,313)	(128,530)	(127,197)
Income Tax Benefit	24,282
Net Loss	$ (93,031)	$ (128,530)	$ (127,197)
Basic and Diluted Net Loss Per Common Share (in dollars per share)	$ (0.72)	$ (1.27)	$ (1.31)
Shares Used in Calculating Basic and Diluted Net Loss per Share (in shares)	128,543	101,529	97,051
COMPREHENSIVE LOSS:
Net Loss	$ (93,031)	$ (128,530)	$ (127,197)
Other Comprehensive Income (Loss):
Foreign Currency Translation Adjustments			15
Unrealized Gain (Loss) on Marketable Securities	23	234	(298)
Comprehensive Loss	$ (93,008)	$ (128,296)	$ (127,480)