Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Capital loss carryforwards	$ 759,000	$ 850,000
Valuation allowance	133,000
Uncertain tax liabilities	0	$ 0	$ 0
Income tax refund	5,633,000
State
Income Taxes [Line Items]
Valuation allowance	133,000
State | 2012
Income Taxes [Line Items]
Capital loss carryforwards	8,300,000
State | 2013
Income Taxes [Line Items]
Capital loss carryforwards	$ 15,300,000