Stock Based Incentive Compensation Plans (Summary of activity for stock options with service conditions) (Details) - Stock options with service conditions [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Summary of activity for stock options [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	2,192,139
Granted - original (in shares) | shares	481,404
Exercised (includes shares tendered) (in shares) | shares	(239,633)
Forfeited or expired (in shares) | shares	(79,894)
Outstanding as of end of year (in shares) | shares	2,354,016
Vested or expected to vest as of end of year (in shares) | shares	2,134,763	[1]
Exercisable as of end of year (in shares) | shares	1,448,275
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 46.02
Weighted average exercise price granted - original (in dollars per share) | $ / shares	77.81
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	33.13
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	67.55
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	53.11
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	52.14	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 44.94
Weighted average remaining contractual term outstanding as of end of year (in years)	6 years 9 months 29 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	6 years 8 months 12 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	5 years 9 months 29 days
Aggregate intrinsic value outstanding as of end of year | $	$ 17
Aggregate intrinsic value vested or expected to vest as of end of year | $	16	[1]
Aggregate intrinsic value exercisable as of end of year | $	$ 14

[1] Includes estimated forfeitures.