Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (2,693)	$ (2,979)
Interest cost on projected benefit obligation	1,618	1,475
Net amortization and deferral	1,406	1,250
Net periodic expense (benefit)	$ 331	$ (254)