Employee benefit plans - Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Employee Benefit Plans
Employer service cost	$ 2,438	$ 1,997	$ 4,960	$ 3,952
Interest cost	62	23	126	45
Expected return on plan assets	(1,035)	(15)	(2,106)	(30)
Amortization of prior service cost	193	54	387	108
Amortization of actuarial losses	89	288	177	576
Net periodic benefit cost	$ 1,747	$ 2,347	$ 3,544	$ 4,651
Location of costs excluding the service component	Other income (expense), net	Other income (expense), net	Other income (expense), net	Other income (expense), net
Expected contributions	$ 6,400		$ 6,400