v3.8.0.1
Stock-Based Compensation - Stock-based Compensation Expense by Type of Award (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total stock-based compensation expense $ 2,498 $ 1,596 $ 802
Tax benefit on exercise of stock options 0 60 40
Stock options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total stock-based compensation expense 738 791 658
Stock appreciation rights (“SARs”)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total stock-based compensation expense 1,543 805 144
Stock grants      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total stock-based compensation expense $ 217 $ 0 $ 0