Pension and Profit Sharing Plans (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Annual contributions, included in employee benefit expense	$ 286,955	$ 210,604
Amount of discretionary employer matching contributions to plan	38,211	21,261
Amount of additional contributions under this plan for benefit of certain employees	$ 1,014	$ 1,014