Stock-Based Compensation (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)	18.6
Shares, granted (in shares)	1.4
Shares, exercised (in shares)	(7.4)
Shares, cancelled, forfeited and expired (in shares)	(0.4)
Options, Ending balance (in shares)	12.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted-average exercise price, Beginning balance	$ 39.58
Weighted-average exercise price, granted	$ 0
Weighted-average exercise price, exercised	$ 37.78
Weighted-average exercise price, cancelled, forfeited and expired	$ 50.33
Weighted-average exercise price, Ending balance	$ 41.78
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares, options exercisable (in shares)	10.9
Weighted-average exercise price, options exercisable	$ 40.55
Weighted-average remaining years of contractual term, Options outstanding at December 31, 2011	4 years 3 months 18 days
Weighted-average remaining years of contractual term, Options exercisable at December 31, 2011	3 years 8 months 12 days
Aggregate intrinsic value, options outstanding at December 31, 2011	$ 445
Aggregate intrinsic value, options exercisable at December 31, 2011	409
Non Vested Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)	1.1
Shares, granted (in shares)	1.4
Shares, vested (in shares)	(1.2)
Options, Ending balance (in shares)	1.3
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	$ 10.61
Weighted-average exercise price, granted	$ 14.46
Weighted-average grant-date fair value, vested	$ 10.61
Weighted-average grant-date fair value, Ending balance	$ 14.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Total unrecognized compensation expense related to nonvested options	$ 9
Weighted-average years to be recognized over	2 years 3 months 18 days