Fair Value Measurement (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Marketable securities
Marketable securities	$ 155,206	$ 190,199
Money market funds
Marketable securities
Marketable securities	54,218	45,948
U.S. treasury securities
Marketable securities
Marketable securities	52,143	74,776
Corporate bonds
Marketable securities
Marketable securities	15,370	8,938
Commercial paper
Marketable securities
Marketable securities	33,475	60,537
Level 1
Marketable securities
Marketable securities	106,361	120,724
Level 1 | Money market funds
Marketable securities
Marketable securities	54,218	45,948
Level 1 | U.S. treasury securities
Marketable securities
Marketable securities	52,143	74,776
Level 1 | Corporate bonds
Marketable securities
Marketable securities	0	0
Level 1 | Commercial paper
Marketable securities
Marketable securities	0	0
Level 2
Marketable securities
Marketable securities	48,845	69,475
Level 2 | Money market funds
Marketable securities
Marketable securities	0	0
Level 2 | U.S. treasury securities
Marketable securities
Marketable securities	0	0
Level 2 | Corporate bonds
Marketable securities
Marketable securities	15,370	8,938
Level 2 | Commercial paper
Marketable securities
Marketable securities	33,475	60,537
Level 3
Marketable securities
Marketable securities	0	0
Level 3 | Money market funds
Marketable securities
Marketable securities	0	0
Level 3 | U.S. treasury securities
Marketable securities
Marketable securities	0	0
Level 3 | Corporate bonds
Marketable securities
Marketable securities	0	0
Level 3 | Commercial paper
Marketable securities
Marketable securities	$ 0	$ 0