Share-Based Compensation (Summary of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Jan. 01, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Number of Stock Options
Outstanding at Beginning of period (in shares)	379,102	379,102
Exercised (in shares)		(27,196)	(8,666)
Forfeited (in shares)		(435)
Outstanding at End of period (in shares)		351,471
Weighted-Average Exercise Price
Outstanding at Beginning of period (in dollars per share)	$ 54.32	$ 54.32
Exercised (in dollars per share)		20.98
Forfeited (in dollars per share)		19.75
Outstanding at End of period (in dollars per share)		$ 56.94
Weighted-Average Remaining Contractual Term (In Years) [Abstract]
Weighted-Average Remaining Contractual Term (in years)	5 years 3 months 7 days	5 years 4 months 24 days
Aggregate Intrinsic Value (In Millions) [Abstract]
Aggregate Intrinsic Value (in millions)		$ 13		$ 20
Stock options, exercisable (in shares)		351,471	400,000
Options exercisable, weighted average exercise price (in dollars per share)		$ 56.94	$ 45.25