Stock-Based Incentive Compensation Plans (Summary of activity for stock appreciation rights plan) (Details) - Non-employee Stock Appreciation Rights [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Summary of activity for stock options [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	264,871
Granted - original (in shares) | shares	63,807
Exercised (includes shares tendered) (in shares) | shares	(87,147)
Forfeited or expired (in shares) | shares	(4,259)
Outstanding as of end of year (in shares) | shares	237,272
Vested or expected to vest as of end of year (in shares) | shares	226,463	[1]
Exercisable as of end of year (in shares) | shares	138,343
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 39.61
Weighted average exercise price granted - original (in dollars per share) | $ / shares	40.06
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	31.36
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	49.01
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	42.59
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	42.66	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 40.42
Weighted average remaining contractual term outstanding as of end of year (in years)	2 years 5 months 23 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	2 years 5 months 12 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	1 year 9 months 22 days
Aggregate intrinsic value outstanding as of end of year | $	$ 6
Aggregate intrinsic value vested or expected to vest as of end of year | $	5	[1]
Aggregate intrinsic value exercisable as of end of year | $	$ 4

[1] Includes estimated forfeitures.