Annual report pursuant to Section 13 and 15(d)

Intangible Assets and Goodwill - Additional Information (Detail)

v3.8.0.1
Intangible Assets and Goodwill - Additional Information (Detail) - USD ($)
6 Months Ended 12 Months Ended
Jun. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]        
Intangible assets and goodwill impairment $ 0      
Goodwill   $ 2,926,000 $ 2,926,000  
Amortization expense   $ 0 $ 51,000 $ 63,000