Income Taxes - Reconciliation of Income Tax Computed at U.S. Federal Statutory Rate to Income Tax Expense (Benefit) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Tax expense (benefit) at U.S. statutory rate, Amount	$ 1,657,000	$ 4,227,000	$ 2,610,000
State and local tax expense (benefit), net of Federal impact, Amount	142,000	494,000	194,000
Impact of state and local tax rate change net of Federal impact, Amount	7,000	(714,000)	27,000
Non-deductible items, Amount	147,000	(2,000)	11,000
Income tax expense (benefit)	$ 1,953,000	$ 4,005,000	$ 2,842,000
Tax expense (benefit) at U.S. statutory rate, percent	35.00%	35.00%	35.00%
State and local tax expense (benefit), net of Federal impact, percent	3.00%	4.09%	2.60%
Impact of state and local tax rate change net of Federal impact, percent	0.15%	(5.90%)	0.36%
Non-deductible items, percent	3.10%	(0.02%)	0.15%
Income tax expense (benefit), percent	41.25%	33.17%	38.11%