Pension and other postretirement benefits - Amounts recognized in consolidated balance sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Payroll and benefit-related liabilities	$ (143,657)	$ (122,366)
Pension and postretirement benefit liabilities	(45,185)	(74,499)
Pension
Defined Benefit Plan Disclosure [Line Items]
Other assets	17,827	3,703
Payroll and benefit-related liabilities	(1,602)	(1,721)
Pension and postretirement benefit liabilities	(21,106)	(45,703)
Accumulated other comprehensive loss (gain)	218,139	232,540
Amounts recognized in balance sheet	213,258	188,819
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Other assets	0	0
Payroll and benefit-related liabilities	(2,725)	(3,125)
Pension and postretirement benefit liabilities	(24,079)	(28,796)
Accumulated other comprehensive loss (gain)	(2,847)	(1,617)
Amounts recognized in balance sheet	$ (29,651)	$ (33,538)