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, 2018 USD ($) $ / shares shares
Summary of activity for stock options [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	271,724
Granted - original (in shares) | shares	32,400
Exercised (includes shares tendered) (in shares) | shares	(55,594)
Forfeited or expired (in shares) | shares	(19,694)
Outstanding as of end of year (in shares) | shares	228,836
Vested or expected to vest as of end of year (in shares) | shares	214,570	[1]
Exercisable as of end of year (in shares) | shares	200,304
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 54.37
Weighted average exercise price granted - original (in dollars per share) | $ / shares	78.41
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	47.13
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	55.45
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	59.43
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	58.54	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 57.51
Weighted average remaining contractual term outstanding as of end of year (in years)	2 years 3 months 7 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	2 years 2 months 5 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	2 years 29 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.