Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Weighted Average Assumptions Use in Calculation of Fair Value for Service and Performance Conditions SARs Awards (Detail)

v3.10.0.1
Share-Based Compensation - Weighted Average Assumptions Use in Calculation of Fair Value for Service and Performance Conditions SARs Awards (Detail)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Service condition awards [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 49.20% 49.60%
Dividend yield 0.00% 0.10%
Expected term 6 years 6 years
Risk-free interest rate 2.20% 1.20%
Performance condition awards [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 49.60% 49.60%
Dividend yield 0.00% 0.00%
Expected term 6 years 1 month 6 days 6 years
Risk-free interest rate 2.20% 1.20%