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, 2015 USD ($) $ / shares shares
Summary of activity for stock options [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	1,071,747
Granted - original (in shares) | shares	90,239
Exercised (includes shares tendered) (in shares) | shares	(131,121)
Forfeited or expired (in shares) | shares	(22,785)
Outstanding as of end of year (in shares) | shares	1,008,080
Vested or expected to vest as of end of year (in shares) | shares	952,889	[1]
Exercisable as of end of year (in shares) | shares	897,697
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 47.93
Weighted average exercise price granted - original (in dollars per share) | $ / shares	57.65
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	39.60
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	40.46
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	50.05
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	49.96	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 49.86
Weighted average remaining contractual term outstanding as of end of year (in years)	2 years 3 months 11 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	2 years 2 months 16 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	2 years 1 month 17 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.