Fair Value Measurements - Schedule of Unrealized Loss on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair value
Less than 12 months	$ 141,657	$ 287,982
12 months or greater	0	1,205
Total	141,657	289,187
Unrealized losses
Less than 12 months	(56)	(114)
12 months or greater	0	0
Total	(56)	(114)
U.S. government agency securities and treasuries
Fair value
Less than 12 months	48,802	211,384
12 months or greater	0	0
Total	48,802	211,384
Unrealized losses
Less than 12 months	(16)	(74)
12 months or greater	0	0
Total	(16)	(74)
Corporate bonds
Fair value
Less than 12 months	92,855	76,598
12 months or greater	0	1,205
Total	92,855	77,803
Unrealized losses
Less than 12 months	(40)	(40)
12 months or greater	0	0
Total	$ (40)	$ (40)