Stock-based compensation - Return target options activity (Details) - Employee Stock Option, Target-Based - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Options (in shares)
Outstanding, beginning balance (in shares)	3,272,920
Granted (in shares)	0	0	0
Exercised (in shares)	(678,298)		0
Forfeitures (in shares)	0
Outstanding, ending balance (in shares)	2,594,622	3,272,920
Options, exercisable (in shares)	2,594,622
Vested or expected to vest (in shares)	2,594,622
Weighted- Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 6.75
Granted (in dollars per share)	0
Exercised (in dollars per share)	7.26
Forfeitures (in dollars per share)	0
Outstanding, ending balance (in dollars per share)	6.61	$ 6.75
Options, exercisable (in dollars per share)	6.61
Vested or expected to vest (in dollars per share)	$ 6.61
Weighted- Average Remaining Contractual Term (Years)
Remaining term, options outstanding	4 years 3 months 18 days	5 years 9 months 18 days
Remaining term, options exercisable	4 years 3 months 18 days
Remaining term, options vested or expected to vest	4 years 3 months 18 days
Aggregate Intrinsic Value (in thousands)
Options outstanding, beginning	$ 47,623
Options outstanding, ending	29,697	$ 47,623
Options exercisable	29,697
Options vested or expected to vest	$ 29,697