Pension and Profit Sharing Plans (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension and Profit Sharing Plans
Annual contributions included in employee benefit expense	$ 362,000	$ 387,000
Employee contributions and profit sharing expenses	307,000	301,000
Amount of discretionary employer matching contributions to plan	$ 55,000	$ 52,000