Stock-Based Compensation (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)	12.2
Shares, granted (in shares)	0.8
Shares, exercised (in shares)	(4.8)
Shares, cancelled, forfeited and expired (in shares)	(0.1)
Options, Ending balance (in shares)	8.1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted-average exercise price, Beginning balance	$ 41.78
Weighted-average exercise price, granted	$ 77.85
Weighted-average exercise price, exercised	$ 72.04
Weighted-average exercise price, cancelled, forfeited and expired	$ 50.96
Weighted-average exercise price, Ending balance	$ 45.18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares, options exercisable (in shares)	6.5
Weighted-average exercise price, options exercisable	$ 40.28
Weighted-average remaining years of contractual term, Options outstanding at December 31, 2014	4 years 9 months 18 days
Weighted-average remaining years of contractual term, Options exercisable at December 31, 2014	3 years 9 months 18 days
Aggregate intrinsic value, options outstanding at December 31, 2014	$ 356
Aggregate intrinsic value, options exercisable at December 31, 2014	317
Non Vested Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)	1.3
Shares, granted (in shares)	0.8
Shares, vested (in shares)	(0.4)
Shares, forfeited (in shares)	(0.1)
Options, Ending balance (in shares)	1.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted-average grant-date fair value, Beginning balance	$ 14.46
Weighted-average exercise price, granted	$ 23.41
Weighted-average grant-date fair value, vested	$ 14.47
Weighted-average exercise price, forfeited	$ 15.68
Weighted-average grant-date fair value, Beginning balance	$ 19.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Total unrecognized compensation expense related to nonvested options	$ 12
Weighted-average years to be recognized over	2 years 1 month 6 days