Pension and other postretirement benefits - Amounts recognized in consolidated balance sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Payroll and benefit-related liabilities	$ (146,535)	$ (133,092)
Pension and postretirement benefit liabilities	(23,989)	(31,394)
Pension
Defined Benefit Plan Disclosure [Line Items]
Other assets	27,370	16,870
Payroll and benefit-related liabilities	(1,439)	(1,408)
Pension and postretirement benefit liabilities	(15,815)	(14,949)
Accumulated other comprehensive loss (gain)	164,139	219,555
Amounts recognized in balance sheet	174,255	220,068
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Other assets	0	0
Payroll and benefit-related liabilities	(1,361)	(2,175)
Pension and postretirement benefit liabilities	(8,174)	(16,445)
Accumulated other comprehensive loss (gain)	(14,244)	(7,812)
Amounts recognized in balance sheet	$ (23,779)	$ (26,432)