Stock-Based Compensation Plans - Summary of Information of Stock Options Exercised (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Abstract]
Aggregate value	[1]	$ 12	$ 15	$ 11
Cash received for exercise price		$ 56	$ 107	$ 19

[1] The difference between the market value on the date of exercise and the option exercise price.