XML 86 R68.htm IDEA: XBRL DOCUMENT v3.8.0.1
Property and Equipment - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property Plant And Equipment [Abstract]      
Depreciation and amortization $ 3.9 $ 3.1 $ 1.9