XML 64 R49.htm IDEA: XBRL DOCUMENT v3.10.0.1
Property Plant and Equipment - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Property, Plant and Equipment [Line Items]      
Depreciation expense   $ 0.1 $ 0.1
Maximum      
Property, Plant and Equipment [Line Items]      
Depreciation expense $ 0.1