Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,072)	$ (2,693)	$ (6,144)	$ (5,386)
Interest cost on projected benefit obligation	1,253	1,618	2,505	3,236
Net amortization and deferral	1,329	1,406	2,659	2,812
Net periodic expense (benefit)	$ (490)	$ 331	$ (980)	$ 662