Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues [Abstract]
Collaboration revenue	$ 3,648	$ 0	$ 0
Contract manufacturing revenue	0	0	9,821
Total collaboration and contract manufacturing revenue	3,648	0	9,821
Operating Expenses [Abstract]
Cost of contract manufacturing	0	0	10,729
Research and development	115,639	100,925	67,449
Selling, general and administrative	60,792	38,950	25,885
Acquired in-process research and development and related costs	251,438	0	0
Loss on contract termination	0	0	478
Change in fair value of contingent consideration	5,600	1,300	24,100
Asset impairment charges	0	0	1,116
Total operating expenses	433,469	141,175	129,757
Loss from operations	(429,821)	(141,175)	(119,936)
Other income (expense):
Interest income	9,804	7,170	1,090
Interest expense	(2)	(6)	(2,644)
Loss on extinguishment of debt	0	0	(4,876)
Change in fair value of common stock warrant liabilities	145	169	297
Other income (expense), net	371	10,126	47
Total other income (expense)	10,318	17,459	(6,086)
Loss from continuing operations	(419,503)	(123,716)	(126,022)
Loss from discontinued operations	0	(198)	(795)
Net loss	$ (419,503)	$ (123,914)	$ (126,817)
Net loss per share, basic and diluted:
Continuing operations (in usd per share)	$ (9.74)	$ (3.27)	$ (4.62)
Discontinued operations (in usd per share)	0	0	(0.03)
Net loss per share, basic and diluted (in dollars per share)	$ (9.74)	$ (3.27)	$ (4.65)
Weighted average common shares outstanding, basic and diluted
Weighted average common shares outstanding, basic and diluted (shares)	43,078	37,884	27,301