Accumulated other comprehensive loss - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 2,704,872
Beginning balance	2,704,872	$ 3,071,722
Amounts reclassified from AOCL	1,111	1,078
Other comprehensive income, net of tax	1,111	1,078
Ending balance	2,797,889	3,151,265
Ending Balance	2,797,889
Total
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(119,610)	(125,533)
Beginning balance	(119,610)	(125,533)
Other comprehensive income, net of tax	1,111	1,078
Ending balance	(118,499)	(124,455)
Ending Balance	(118,499)	(124,455)
Retirement Plans
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(120,142)	(126,065)
Amounts reclassified from AOCL	1,111	1,078
Other comprehensive income, net of tax	1,111	1,078
Ending balance	(119,031)	(124,987)
Foreign Currency
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	532	532
Amounts reclassified from AOCL
Other comprehensive income, net of tax
Ending Balance	$ 532	$ 532