Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (2,693)	$ (2,979)	$ (5,386)	$ (5,958)
Interest cost on projected benefit obligation	1,618	1,474	3,236	2,949
Net amortization and deferral	1,406	1,251	2,812	2,501
Net periodic expense (benefit)	$ 331	$ (254)	$ 662	$ (508)