Stock Incentive Plans - Summary of Stock Options Exercised (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
Proceeds from stock options exercised | $ 2 | $ 2 | $ 8 |
Tax benefit recognized from stock options exercised | 0 | 0 | 2 |
Intrinsic value of stock options exercised | $ 1 | $ 1 | $ 7 |