Fair value measurements - Assets and liabilities measured on a recurring basis - (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 112,525	$ 68,802
Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Total money market funds and marketable securities	339,326	227,663
Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Total money market funds and marketable securities	209,067	199,708
Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Total money market funds and marketable securities	130,259	27,955
U.S. Treasury notes | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	77,920	103,044
U.S. Treasury notes | Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	77,920	103,044
U. S. Government agency securities | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	24,655	31,075
U. S. Government agency securities | Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	24,655	31,075
Corporate bonds | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	102,083	23,970
Corporate bonds | Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	102,083	23,970
Commercial paper | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	22,715	3,985
Commercial paper | Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	22,715	3,985
Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	106,492	65,589
Money market funds | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	106,492	65,589
Money market funds | Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	106,492	$ 65,589
Certificates of deposits | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	5,461
Certificates of deposits | Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	$ 5,461