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, 2016 USD ($) $ / shares shares
Summary of activity for stock options [Roll Forward]
Outstanding as of beginning of year (in shares) | shares	1,008,080
Granted - original (in shares) | shares	92,310
Exercised (includes shares tendered) (in shares) | shares	(297,858)
Forfeited or expired (in shares) | shares	(22,716)
Outstanding as of end of year (in shares) | shares	779,816
Vested or expected to vest as of end of year (in shares) | shares	734,680	[1]
Exercisable as of end of year (in shares) | shares	689,544
Summary of activity for stock options, additional disclosures [Abstract]
Weighted average exercise price as of beginning of year (in dollars per share) | $ / shares	$ 50.05
Weighted average exercise price granted - original (in dollars per share) | $ / shares	40.07
Weighted average exercise price exercised (includes shares tendered) (in dollars per share) | $ / shares	47.66
Weighted average exercise price forfeited or expired (in dollars per share) | $ / shares	48.17
Weighted average exercise price outstanding as of end of year (in dollars per share) | $ / shares	49.83
Weighted average exercise price vested or expected to vest as of end of year (in dollars per share) | $ / shares	49.85	[1]
Weighted average exercise price exercisable as of end of year (in dollars per share) | $ / shares	$ 49.87
Weighted average remaining contractual term outstanding as of end of year (in years)	1 year 8 months 19 days
Weighted average remaining contractual term vested or expected to vest as of end of year (in years)	1 year 7 months 10 days	[1]
Weighted average remaining contractual term exercisable as of end of year (in years)	1 year 6 months
Aggregate intrinsic value outstanding as of end of year | $	$ 13
Aggregate intrinsic value vested or expected to vest as of end of year | $	12	[1]
Aggregate intrinsic value exercisable as of end of year | $	$ 11

[1] Includes estimated forfeitures.