v3.10.0.1
Share-based Compensation - Summary of Stock Options and Changes (Long Term Incentive Plans) (Detail) - Long Term Incentive Plans [Member] - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended 36 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options, Outstanding at January 1, 2018 2,981,033    
Stock options, Granted 0 0 0
Stock options, Exercised 803,391    
Stock options, Forfeited 73,554    
Stock options, Outstanding at December 31, 2018 2,104,088 2,981,033 2,104,088
Stock options, Exercisable at December 31, 2018 1,583,001   1,583,001
Weighted average exercise price, Outstanding at January 1, 2018 $ 48.39    
Weighted average exercise price, Granted 0    
Weighted average exercise price, Exercised 37.13    
Weighted average exercise price, Forfeited 73.43    
Weighted average exercise price, Outstanding at December 31, 2018 51.81 $ 48.39 $ 51.81
Weighted average exercise price, Exercisable at December 31, 2018 $ 43.14   $ 43.14
Weighted average remaining contractual term, Outstanding at December 31, 2018 4 years 8 months 12 days    
Weighted average remaining contractual term, Exercisable at December 31, 2018 4 years 1 month 6 days    
Aggregate intrinsic value, Outstanding at December 31, 2018 $ 49   $ 49
Aggregate intrinsic value, Exercisable at December 31, 2018 $ 48   $ 48