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, 2015 USD ($) $ / shares shares
Summary of activity for stock options [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	307,959
Granted - original (in shares) | shares	48,451
Exercised (includes shares tendered) (in shares) | shares	(85,713)
Forfeited or expired (in shares) | shares	(5,826)
Outstanding as of end of year (in shares) | shares	264,871
Vested or expected to vest as of end of year (in shares) | shares	248,111	[1]
Exercisable as of end of year (in shares) | shares	155,909
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 34.28
Weighted average exercise price granted - original (in dollars per share) | $ / shares	57.64
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	30.18
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	38.92
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	39.61
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	39.70	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 35.01
Weighted average remaining contractual term outstanding as of end of year (in years)	2 years 3 months 29 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	2 years 3 months 26 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	1 year 9 months 15 days
Aggregate intrinsic value outstanding as of end of year | $	$ 3
Aggregate intrinsic value vested or expected to vest as of end of year | $	3	[1]
Aggregate intrinsic value exercisable as of end of year | $	$ 2

[1] Includes estimated forfeitures.