Annual report pursuant to Section 13 and 15(d)

Stock-based Compensation - Valuation Assumptions (Details)

v3.8.0.1
Stock-based Compensation - Valuation Assumptions (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (in years) 6 years 6 months 6 years 6 months
Volatility 37.00% 37.00%
Dividend yield 0.00% 0.00%
Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 1.86% 1.13%
Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 2.00% 1.24%