Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (2,693)	$ (2,979)	$ (8,079)	$ (8,937)
Interest cost on projected benefit obligation	1,618	1,475	4,854	4,424
Net amortization and deferral	1,406	1,250	4,218	3,751
Net periodic expense (benefit)	$ 331	$ (254)	$ 993	$ (762)