Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Federal (net of state benefit) - enactment of tax reform	$ 1,100,000
Amount for which no federal income tax provision has been made	6,000,000	$ 6,000,000	$ 6,000,000
Unrecognized Tax Benefits	0	0
Accrued Interest Or Penalties	0	$ 0
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 52,600,000
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2018
Minimum [Member]
Income Tax Contingency [Line Items]
Open tax years	2014