Share-Based Compensation (Stock Option and SAR Activity) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period, Shares	112
Granted, Shares	1
Exercised, Shares	(18)
Forfeited, Shares	(4)
Share Based Compensation Arrangement By Share Based Payment Award Options And Sars Outstanding Number	91
Exercisable at end of period, Shares	74
Vested and expected to vest end of period, Shares	91
Outstanding at beginning of period, Weighted-Average Exercise Price	$ 40
Granted, Weighted-Average Exercise Price	$ 44
Exercised, Weighted-Average Exercise Price	$ 29
Forfeited, Weighted-Average Exercise Price	$ 44
Outstanding at end of period, Weighted-Average Exercise Price	$ 42
Exercisable at end of period, Weighted-Average Exercise Price	$ 44
Vested and expected to vest end of period, Weighted-Average Exercise Price	$ 42
Outstanding at end of period, Weighted-Average Remaining Contractual Life (in years)	4.7
Exercisable at end of period, Weighted-Average Remaining Contractual Life (in years)	4.1
Vested and expected to vest end of period, Weighted-Average Remaining Contractual Life (in years)	4.7
Outstanding at end of period, Aggregate Intrinsic Value	$ 916
Exercisable at end of period, Aggregate Intrinsic Value	610
Vested and expected to vest end of period, Aggregate Intrinsic Value	$ 905