CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues	$ 82,271,000	$ 53,446,000	$ 115,447,000
Operating expenses:
Research and development	114,522,000	174,456,000	139,739,000
General and administrative	38,489,000	36,746,000	33,911,000
Restructuring charge	21,433,000	3,693,000	779,000
Total operating expenses	174,444,000	214,895,000	174,429,000
Loss from operations	(92,173,000)	(161,449,000)	(58,982,000)
Investment income, net	4,424,000	4,227,000	1,146,000
Non-cash interest expense on liability related to the sale of future royalties and convertible senior notes	(16,879,000)	(10,631,000)	(13,682,000)
Interest expense on convertible senior notes	(95,000)	(95,000)	(3,040,000)
Non-cash debt conversion expense			(22,915,000)
Other income (expense), net	590,000	(895,000)	1,461,000
Net loss	$ (104,133,000)	$ (168,843,000)	$ (96,012,000)
Basic and diluted net loss per common share (in dollar per share)	$ (0.70)	$ (1.21)	$ (0.98)
Basic and diluted weighted average common shares outstanding (in shares)	148,311	139,946	98,068
Total comprehensive loss	$ (104,133,000)	$ (168,843,000)	$ (96,012,000)
License and milestone fees
Revenues:
Total revenues	34,788,000	15,280,000	79,469,000
Non-cash royalty revenue related to the sale of future royalties
Revenues:
Total revenues	47,415,000	32,154,000	28,142,000
Research and development support
Revenues:
Total revenues	$ 68,000	1,377,000	3,482,000
Clinical materials revenue
Revenues:
Total revenues		$ 4,635,000	$ 4,354,000