v3.8.0.1
Summary of Significant Accounting Policies - Property (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property and Equipment      
Estimated useful life P3Y    
Impairment of assets $ 576 $ 2,138 $ 1,557
Machinery and equipment      
Property and Equipment      
Impairment of assets   $ 2,100