Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue:
License and collaboration revenue—related party	$ 147,872	$ 65,201
Operating expenses:
Research and development	67,135	70,052
General and administrative	27,920	26,443
Total operating expenses	95,055	96,495
Operating income (loss)	52,817	(31,294)
Other income, net	4,052	3,961
Income (loss) before provision for income taxes	56,869	(27,333)
Provision for income taxes	46	46
Net income (loss)	$ 56,823	$ (27,379)
Net income (loss) per share, basic (in dollars per share)	$ 1.72	$ (0.84)
Net income (loss) per share, diluted (in dollars per share)	$ 1.66	$ (0.84)
Weighted-average common shares outstanding, basic (in shares)	33,080	32,567
Weighted-average common shares outstanding, diluted (in shares)	34,294	32,567
Comprehensive income (loss):
Net income (loss)	$ 56,823	$ (27,379)
Other comprehensive income:
Unrealized gain on available-for-sale securities	132	331
Comprehensive income (loss)	$ 56,955	$ (27,048)