Stock-Based Compensation Plans (Summary Of The Activity For Stock Options) (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Number of Options
Number of Options, Outstanding at beginning of year | shares	4.2
Number of Options, Granted | shares	0.1
Number of Options, Exercised | shares	(1.9)
Number of Options, Cancelled | shares	0.0
Number of Options, Expired | shares	0.0
Number of Options, Outstanding at end of period | shares	2.4
Number of Options, Vested and expected to vest at end of year | shares	2.4
Number of Options, Exercisable at end of year | shares	2.3
Weighted Average Exercise Price (in dollars)
Weighted Average Exercise Price, Outstanding at beginning of year | $ / shares	$ 19.09
Weighted Average Exercise Price, Granted | $ / shares	59.64
Weighted Average Exercise Price, Exercised | $ / shares	18.07
Weighted Average Exercise Price, Cancelled | $ / shares	0.00
Weighted Average Exercise Price, Expired | $ / shares	0.00
Weighted Average Exercise Price, Outstanding at end of year | $ / shares	21.08
Weighted Average Exercise Price, Vested and expected to vest at end of year | $ / shares	20.95
Weighted Average Exercise Price, Exercisable at end of year | $ / shares	$ 19.36
Weighted Average Remaining Life, Outstanding at end of year (in years)	1 year 7 months 6 days
Weighted Average Remaining Life, Vested and expected to vest at end of year (in years)	1 year 6 months
Weighted Average Remaining Life, Exercisable at end of year (in years)	1 year 3 months 15 days
Aggregate Intrinsic Value, Outstanding at end of year | $	$ 84
Aggregate Intrinsic Value, Vested and expected to vest at end of year | $	84
Aggregate Intrinsic Value, Exercisable at end of year | $	$ 84