Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

v3.10.0.1
Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Income Tax Disclosure [Abstract]          
Federal and state income tax expense (benefit) $ 800,000 $ 900,000 $ 1,900,000 $ (1,300,000)  
Interest or penalties related to uncertain tax positions     0 $ 0  
Prepaid taxes 200,000   200,000   $ 100,000
Deferred tax assets 2,300,000   2,300,000   3,600,000
Deferred tax liability $ 1,500,000   $ 1,500,000   $ 1,700,000
Tax years open to examination     2013 2017    
Corporate income tax rate     21.00%   35.00%