Retirement plans - Schedule of Changes in Projected Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in benefit obligations
Benefit obligations as of end of year	$ 462,466
Change in plan assets
Fair value of plan assets as of end of year	386,108
Funded status as of end of year	(76,358)
Amounts recognized in Consolidated Balance Sheets
Pension liabilities—non-current	(70,483)	$ (73,684)
Retirement Plans
Change in benefit obligations
Benefit obligations as of beginning of year	464,309	605,834
Interest cost	24,183	16,830	$ 15,887
Actuarial loss (gain)	9,443	(119,462)
Benefits paid	(35,469)	(36,943)
Settlements	0	(1,950)
Benefit obligations as of end of year	462,466	464,309	605,834
Change in plan assets
Fair value of plan assets as of beginning of year	385,005	541,758
Actual gains (losses) experienced by plan assets	32,739	(123,648)
Employer contributions	3,833	5,788
Benefits paid	(35,469)	(36,943)
Settlements	0	(1,950)
Fair value of plan assets as of end of year	386,108	385,005	$ 541,758
Funded status as of end of year	(76,358)	(79,304)
Amounts recognized in Consolidated Balance Sheets
Accrued liabilities other—current	(5,875)	(5,620)
Pension liabilities—non-current	$ (70,483)	$ (73,684)