Fair value of financial instruments - Cash, cash equivalents and marketable securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Net Investment Income [Line Items]
Cost	$ 60,247	$ 81,224
Gross Unrealized Losses		(6)
Estimated Fair Value	60,247	81,218
Cash and cash equivalents
Net Investment Income [Line Items]
Cost	60,247	74,229
Estimated Fair Value	$ 60,247	74,229
Marketable securities
Net Investment Income [Line Items]
Cost		6,995
Gross Unrealized Losses		(6)
Estimated Fair Value		6,989
U.S. Treasury securities due in one year or less
Net Investment Income [Line Items]
Cost		6,995
Gross Unrealized Losses		(6)
Estimated Fair Value		$ 6,989