Annual report pursuant to Section 13 and 15(d)

Property and Equipment - Additional Information (Detail)

v3.8.0.1
Property and Equipment - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Property, Plant and Equipment [Abstract]    
Fully depreciated computer software and hardware and furniture, fixtures and equipment write-off $ 2.9 $ 2.8