Stock Based Incentive Compensation Plans (Summary of activity for stock options with performance conditions) (Details) - Stock options with performance conditions [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Shares
Outstanding as of beginning of year (in shares) | shares	228,836
Granted - original (in shares) | shares	35,878
Exercised (includes shares tendered) (in shares) | shares	(41,898)
Forfeited or expired (in shares) | shares	(13,712)
Outstanding as of end of year (in shares) | shares	209,104
Vested or expected to vest as of end of year (in shares) | shares	198,345	[1]
Exercisable as of end of year (in shares) | shares	187,585
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 59.43
Weighted average exercise price granted - original (in dollars per share) | $ / shares	61.80
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	50.78
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	65.59
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	61.17
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	60.89	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 60.58
Weighted average remaining contractual term outstanding as of end of year (in years)	2 years 25 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	1 year 11 months 15 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	1 year 10 months 6 days
Aggregate intrinsic value outstanding as of end of year | $	$ 1
Aggregate intrinsic value vested or expected to vest as of end of year | $	1	[1]
Aggregate intrinsic value exercisable as of end of year | $	$ 1

[1] Includes estimated forfeitures.