Postretirement Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (income)	$ (417)	$ (330)	$ (827)	$ (663)
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1,652	1,731	3,303	3,462
Expected return on plan assets	(2,124)	(2,133)	(4,240)	(4,266)
Amortization of net actuarial (gain) loss	(3)	(6)	(6)	(12)
Net periodic benefit cost (income)	(475)	(408)	(943)	(816)
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	160	169	321	333
Expected return on plan assets	(182)	(175)	(365)	(345)
Amortization of net actuarial (gain) loss	80	84	160	165
Net periodic benefit cost (income)	$ 58	$ 78	$ 116	$ 153