Defined Contribution Plans, Pension and Other Post-Retirement Benefit Plans - Fair Value of Pension Plan Assets Measured Using Significant Unobservable Inputs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Change in plan assets:
Fair value of plan assets — Beginning of the year	$ 80,423
Fair value of plan assets at end of the year	73,386	$ 80,423
Level 3
Change in plan assets:
Fair value of plan assets — Beginning of the year	10,153	9,409
Actual return on assets held at reporting date	809	744
Fair value of plan assets at end of the year	$ 10,962	$ 10,153