Deferred Revenue - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Current deferred revenue	$ 75,699	$ 60,994
Deferred revenue, less current portion	187,462	219,332
Revenue recognized	(30,003)
Deferred Revenue
Disaggregation Of Revenue [Line Items]
Revenue recognized	27,300
Development Revenue
Disaggregation Of Revenue [Line Items]
Current deferred revenue	59,169	48,512
Deferred revenue, less current portion	186,572	217,873
Development Revenue | Genentech, Inc.
Disaggregation Of Revenue [Line Items]
Current deferred revenue	56,800	48,100
Deferred revenue, less current portion	$ 184,500	$ 216,800