Retirement Plans - Defined Benefit Pension Plans (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Transition obligation	$ 7,000	$ 7,000
Prior service cost	(75,000)	(115,000)
Net actuarial loss	4,782,000	5,843,000
Amount included in accumulated other comprehensive loss	4,714,000	5,735,000
Deferred tax benefit	(1,982,000)	(2,411,000)
Amount included in accumulated other comprehensive loss, net of tax	$ 2,732,000	$ 3,324,000