Retirement plans - Schedule of Changes in Projected Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Change in benefit obligations
Benefit obligations as of end of year	$ 464,309
Change in plan assets
Fair value of plan assets as of end of year	385,005
Funded status as of end of year	(79,304)
Amounts recognized in Consolidated Balance Sheets
Pension liabilities—non-current	(73,684)	$ (58,063)
Retirement Plans
Change in benefit obligations
Benefit obligations as of beginning of year	605,834	646,662
Service cost	0	2	$ 7
Interest cost	16,830	15,887	19,487
Actuarial gains	(119,462)	(18,246)
Benefits paid	(36,943)	(35,874)
Settlements	(1,950)	(2,597)
Benefit obligations as of end of year	464,309	605,834	646,662
Change in plan assets
Fair value of plan assets as of beginning of year	541,758	552,996
Actual (losses) gains experienced by plan assets	(123,648)	20,896
Employer contributions	5,788	6,337
Benefits paid	(36,943)	(35,874)
Settlements	(1,950)	(2,597)
Fair value of plan assets as of end of year	385,005	541,758	$ 552,996
Funded status as of end of year	(79,304)	(64,076)
Amounts recognized in Consolidated Balance Sheets
Accrued liabilities other—current	(5,620)	(6,013)
Pension liabilities—non-current	$ (73,684)	$ (58,063)