Postretirement Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ (255)	$ (410)
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1,700	1,651
Expected return on plan assets	(2,002)	(2,116)
Amortization of net actuarial (gain) loss	(19)	(3)
Net periodic benefit cost	(321)	(468)
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	168	161
Expected return on plan assets	(194)	(183)
Amortization of net actuarial (gain) loss	92	80
Net periodic benefit cost	$ 66	$ 58