Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Amortized cost of short-term marketable securities	$ 540,016	$ 564,036
Amortized cost of long-term marketable securities	$ 30,681	$ 118,429
Preferred stock par value	$ 0.0001	$ 0.0001
Preferred stock authorized	10,000,000	10,000,000
Preferred stock issued	0	0
Preferred stock outstanding	0	0
Common stock par value	$ 0.0001	$ 0.0001
Common stock authorized	340,000,000	340,000,000
Common stock issued	139,884,698	137,646,896
Common stock outstanding	139,884,698	137,646,896