Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,073)	$ (2,693)	$ (9,217)	$ (8,079)
Interest cost on projected benefit obligation	1,252	1,618	3,757	4,854
Net amortization and deferral	1,330	1,406	3,989	4,218
Net periodic expense (benefit)	$ (491)	$ 331	$ (1,471)	$ 993