Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Related party, receivable from collaboration partners	$ 1,324	$ 943
Related party, deferred revenue - current	67,571	67,571
Related party, deferred revenue - noncurrent	102,386	117,808
Related party, other long-term liabilities	$ 9,703	$ 9,703
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	71,374,059	65,114,685
Common stock, shares outstanding	71,374,059	65,114,685
Common stock, shares outstanding includes shares issued but subject to vesting	1,331,269	1,422,784