Pension and Profit Sharing Plans - Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Service cost - benefits earned during the period	$ 0	$ 0	$ 0
Interest cost on projected benefit obligation	635	665	622
Expected return on plan assets	(974)	(912)	(948)
Amortization of unrecognized net loss	249	375	222
Recognized loss on partial settlement of certain participant balances		267
Net periodic pension benefit expense (benefit)	$ (90)	$ 395	$ (104)