v3.20.4
Share-based Compensation - Summary of Stock Options and Changes (Long Term Incentive Plans) (Detail) - Long Term Incentive Plans
$ / shares in Units, $ in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
$ / shares
shares
Stock options  
Stock options, Outstanding at January 1, 2019 (in shares) | shares 1,202,909
Stock options, Granted (in shares) | shares 0
Stock options, Exercised (in shares) | shares 547,174
Stock options, Forfeited (in shares) | shares 11,401
Stock options, Outstanding at December 31, 2019 (in shares) | shares 644,334
Exercisable at December 31, 2019 (in shares) | shares 644,334
Weighted  average exercise price  in USD  
Weighted average exercise price, Outstanding at January 1, 2018 (in dollars per share) | $ / shares $ 52.08
Weighted average exercise price, Granted (in dollars per share) | $ / shares 0
Weighted average exercise price, Exercised (in dollars per share) | $ / shares 47.77
Weighted average exercise price, Forfeited (in dollars per share) | $ / shares 35.53
Weighted average exercise price, Outstanding at December 31, 2018 (in dollars per share) | $ / shares 56.03
Weighted average exercise price, Exercisable at December 31, 2018 (in dollars per share) | $ / shares $ 56.03
Weighted average remaining contractual term, Outstanding at December 31, 2018 3 years 5 months 15 days
Weighted average remaining contractual term, Exercisable at December 31, 2018 3 years 5 months 15 days
Aggregate intrinsic value, Outstanding at December 31, 2018 | $ $ 66
Aggregate intrinsic value, Exercisable at December 31, 2018 | $ $ 66