Annual report pursuant to Section 13 and 15(d)

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

v3.3.1.900
Share-Based Compensation - Weighted Average Assumptions Use in Calculation of Fair Value for Service, Performance Condition, and Market and Performance Condition Awards (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
SARs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 48.70% 51.50% 50.80%
Dividends yield 1.60% 1.30% 1.70%
Expected term 5 years 9 months 18 days 5 years 7 months 6 days 5 years 6 months
Risk-free interest rate 1.60% 1.70% 1.50%
Independent Directors' SARs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility     45.20%
Dividends yield     1.50%
Expected term     3 years 7 months 6 days
Risk-free interest rate     0.70%
Performance condition awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility 48.80% 52.00% 50.90%
Dividends yield 1.60% 1.30% 1.50%
Expected term 5 years 9 months 18 days 5 years 7 months 6 days 5 years 6 months
Risk-free interest rate 1.60% 1.70% 1.60%