Stock Compensation Plans Level 4 Stock Option Awards (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	3,800	3,745
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 33.09	$ 29.64
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	6 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 45
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	862
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	754
Share-based Compensation Arrangement by Share-based Payment Award Options Exercised in Period Weighted Average Exercise Price	$ 22.18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	0
Share-based Compensation Arrangement by Share-based Payment Award Options Forfeited in Period Weighted Average Exercise Price	$ 0.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	53
Share-based Compensation Arrangement by Share-based Payment Award Options Expired in Period Weighted Average Exercise Price	$ 76.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	3,749
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 33.53
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	6 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 42
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	2,351
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 30.34
Share-based Compensation Arrangement by Share-based Payment Award Option Exercisable Weighted Average Remaining Contractual Term	5 years 2 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 36
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 41.25
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 16	$ 10	$ 5
Employee Stock Option [Member]
The risk-free rate for periods within the contractual life of the option
Expected dividend yield	1.80%	1.70%	1.70%
Expected annualized spot volatility minimum	22.10%	25.90%	31.10%
Expected annualized spot volatility maximum	39.40%	57.80%	48.10%
Weighted average annualized volatility	32.70%	35.10%	47.30%
Risk-free spot rate minimum	0.00%	0.10%	0.10%
Risk-free spot rate maximum	2.60%	2.80%	1.90%
Expected term	5 years	5 years	5 years