Components of Net Periodic Pension Cost Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 689	$ 721	$ 926
Interest cost	4,063	4,465	4,997
Expected return on plan assets	(5,197)	(5,862)	(5,708)
Amortization of actuarial loss		863	3,072
Net periodic cost	$ (445)	$ 187	$ 3,287