Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment - Additional Information (Detail)

v3.8.0.1
Property and Equipment - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Property, Plant and Equipment [Line Items]          
Gross property and equipment $ 13,340   $ 13,340   $ 11,726
Depreciation expense 146 $ 81 414 $ 150  
Asset Under Construction [Member]          
Property, Plant and Equipment [Line Items]          
Gross property and equipment $ 1,374   $ 1,374   $ 37