Stock-Based Compensation (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012		Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)			27.0
Shares, granted (in shares)			0.7	[1]
Shares, exercised (in shares)			(8.4)
Shares, cancelled, forfeited and expired (in shares)			(0.7)
Options, Ending balance (in shares)	18.6		18.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted-average exercise price, Beginning balance			$ 39.96
Weighted-average exercise price, exercised			$ 35.61
Weighted-average exercise price, cancelled, forfeited and expired			$ 52.85
Weighted-average exercise price, Ending balance	$ 39.58		$ 39.58
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares, options exercisable (in shares)	17.5		17.5
Weighted-average exercise price, options exercisable	$ 39.71		$ 39.71
Weighted-average remaining years of contractual term, Options outstanding at December 31, 2011			4 years 1 month 6 days
Weighted-average remaining years of contractual term, Options exercisable at December 31, 2011			3 years 9 months 18 days
Aggregate intrinsic value, options outstanding at December 31, 2011	$ 288		$ 288
Aggregate intrinsic value, options exercisable at December 31, 2011	270		270
Non Vested Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance (in shares)			3.6
Shares, vested (in shares)	(2.4)	[2]
Shares, forfeited (in shares)	(0.1)
Options, Ending balance (in shares)	1.1		1.1
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			$ 10.41
Weighted-average grant-date fair value, vested	$ 10.34	[2]
Weighted-average grant-date fair value, forfeited	$ 10.41
Weighted-average grant-date fair value, Ending balance	$ 10.61		$ 10.61
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Total unrecognized compensation expense related to nonvested options	$ 1		$ 1
Weighted-average years to be recognized over			3 months 18 days

[1] These shares relate to the adjustment in connection with the special dividend announced in the fourth quarter of 2012 and, as such, a weighted average exercise price was not calculated.

[2] The majority of the share adjustment that was recorded in connection with the special dividend announced in the fourth quarter of 2012 related to options that have previously vested, therefore, the shares granted were offset by the equivalent vested amount.