Share-Based Compensation - Summary of Non-qualified Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted- Average Exercise Price
Income tax benefit	$ 9	$ 10	$ 11
Non-qualified Stock Options
Non-qualified Options
Outstanding at beginning of year (in shares)	0	15,705	154,551
Granted (in shares)	0	0	0
Exercised (in shares)	0	(15,705)	(132,905)
Forfeited (in shares)	0	0	0
Expired (in shares)	0	0	(5,941)
Outstanding at end of year (in shares)	0	0	15,705
Shares, Exercisable at end of period (in shares)	0	0	15,705
Weighted- Average Exercise Price
Outstanding at beginning of year (in USD per share)	$ 0	$ 26.34	$ 35.96
Granted (in USD per share)	0	0	0
Exercised (in USD per share)	0	26.34	36.86
Forfeited (in USD per share)	0	0	0
Expired (in USD per share)	0	0	41.25
Outstanding at end of year (in USD per share)	0	0	26.34
Exercisable at end of year (in USD per share)	$ 0	$ 0	$ 26.34
Intrinsic value for options exercised		$ 2	$ 8
Cash received from the exercise of options		1	5
Income tax benefit		$ 2	$ 2
Options vested in period	0	0	0