Pension and Profit Sharing Plans - Benefit Obligation Activity and Fair Value of Plan Assets and Statement of Funded Status (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 523,000	$ 635,000	$ 665,000
Actuarial (gain) loss	(1,717,000)	(3,597,000)
Benefits paid, including settlement of certain participant balances	(1,546,000)
Employer contributions	0	0
Fair value of plan assets at December 31	8,781,000
Reconciliation of Benefit Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at January 1	15,531,000	15,453,000
Interest cost on projected benefit obligation	523,000	635,000
Actuarial (gain) loss	(811,000)	486,000
Benefits paid, including settlement of certain participant balances	(8,630,000)	(1,043,000)
Benefit obligation at December 31	6,613,000	15,531,000	15,453,000
Reconciliation of Fair Value of Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	17,046,000	15,787,000
Actual return on plan assets	365,000	2,302,000
Employer contributions	0	0
Benefits paid, including settlement of certain participant balances	(8,630,000)	(1,043,000)
Fair value of plan assets at December 31	8,781,000	17,046,000	$ 15,787,000
Funded status	$ 2,168,000	$ 1,515,000