Stock-Based Compensation (Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock Options Outstanding, Beginning	2,125
Stock options, Granted	334
Stock options, Exercised	(348)
Stock options, Forfeited	(71)
Stock Options Outstanding, Ending	2,040	2,125
Options exercisable, Shares	1,432
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Outstanding, Beginning	$ 43.08
Weighted Average Exercise Price / Share, Granted	74.08
Weighted Average Exercise Price / Share, Exercised	35.56
Weighted Average Exercise Price / Share, Forfeited	67.97
Weighted Average Exercise Price, Outstanding, Ending	48.56	$ 43.08
Options exercisable, Weighted Average Exercise Price	$ 39.83
Weighted Average Remaining Contractual Term, Outstanding	6 years 3 months 18 days	6 years 6 months
Aggregate intrinsic value of outstanding stock options	$ 62
Weighed average remaining contractual term, Options exercisable	5 years 3 months 18 days
Aggregate intrinsic value of exercisable stock options	$ 56
Vested and non-vested expected to vest as of December 31, 2019	1,996
Vested and non-vested expected to vest as of December 31, 2019	$ 48.00
Vested and non-vested expected to vest as of December 31, 2019	6 years 2 months 12 days
Aggregate intrinsic value, vested and expected to vest	$ 61