CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Revenues	$ 49,593	$ 29,485
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 42,814	$ 36,376
General and administrative	9,572	9,674
Total operating expenses	52,386	46,050
Loss from operations	(2,793)	(16,565)
Interest income	1,075	2,496
Other income (expense)	12	(61)
Loss before income taxes	(1,706)	(14,130)
Benefit from income taxes	(13,911)	(6)
Net income (loss)	$ 12,205	$ (14,124)
Net income (loss) per share
Basic	$ 0.27	$ (0.31)
Diluted	$ 0.26	$ (0.31)
Shares used to compute net income (loss) per share
Basic	45,723,955	45,122,456
Diluted	47,044,774	45,122,456
Other comprehensive income:
Unrealized gain on short-term investments, net of tax	$ 279	$ 155
Impact of adoption of new accounting pronouncement		11
Comprehensive income (loss)	$ 12,484	$ (13,958)