Fair value measurements - Assets and liabilities measured on a recurring basis - (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 143,078	$ 68,802	$ 268,321
Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value	305,934	227,663
Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value	212,121	199,708
Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value	93,813	27,955
U.S. Treasury notes | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	24,486	103,044
U.S. Treasury notes | Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	24,486	103,044
U. S. Government agency securities | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	138,191	31,075
U. S. Government agency securities | Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	138,191	31,075
Corporate bonds | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	88,983	23,970
Corporate bonds | Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	88,983	23,970
Commercial paper | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	4,830	3,985
Commercial paper | Level 2 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Marketable securities	4,830	3,985
Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	49,444	65,589
Money market funds | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	49,444	65,589
Money market funds | Level 1 | Fair value, measurements, recurring
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	$ 49,444	$ 65,589