Income Taxes - Components of Income Tax Expense (Benefit) (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Current Federal alternative minimum tax ("AMT") expense	$ 16,000	$ 79,000	$ 35,000	$ 141,000
Current state and local tax expense	16,000	99,000	188,000	160,000
Deferred Federal tax expense (benefit)	103,000	434,000	(370,000)	1,245,000
Deferred state and local tax expense (benefit)	6,000	(32,000)	(134,000)	21,000
Income tax expense (benefit)	$ 141,000	$ 580,000	$ (281,000)	$ 1,567,000