Share-Based Incentive Compensation (details) - Original and Reload Grants (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Original grants [Member]
Share-based compensation
Expected term of stock options (in years)	6 years	6 years	6 years
Weighted average volatility (percent)	28.60%	28.20%	28.40%
Expected annual dividend per share	$1.64 - $1.84	$1.44 - $1.64	$1.32 - $1.44
Stock options granted, number	2,442,017
Stock options granted, weighted average exercise price	$ 59.75
Stock options granted, weighted average grant-date fair value of options granted (per share)	$ 12.08	$ 12.94	$ 11.94
Total intrinsic value of options exercised during the year	$ 102	$ 76	$ 77
Term of share-based compensation awards	Stock option awards granted to eligible officers and key employees have a ten-year term. Prior to January 1, 2007, stock options were granted with an exercise price equal to the fair market value of the Company's common stock on the day preceding the date of grant. Beginning January 1, 2007, all stock options are granted with an exercise price equal to the closing price of the Company's common stock on the date of grant. The stock options granted generally vest upon meeting certain years of service criteria. Except as the Compensation Committee of the Board may allow in the future, stock options cannot be sold or transferred by the participant. The stock options granted under the 2004 Incentive Plan vest three years after grant date (cliff vest).
Original grants [Member] | Minimum [Member]
Share-based compensation
Expected volatility rate of the Company's stock	28.50%	28.00%	28.30%
Risk-free rate	1.02%	1.19%	1.68%
Original grants [Member] | Maximum [Member]
Share-based compensation
Expected volatility rate of the Company's stock	28.60%	28.60%	29.10%
Risk-free rate	1.17%	2.62%	2.71%
Reload grants [Member]
Share-based compensation
Expected term of stock options (in years)	1 year	1 year
Weighted average volatility (percent)	23.40%	15.90%	21.10%
Expected annual dividend per share	$1.64 - $1.84	$1.44 - $1.64	$1.32 - $1.44
Stock options granted, number	4,920
Stock options granted, weighted average exercise price	$ 63.80
Stock options granted, weighted average grant-date fair value of options granted (per share)	$ 4.49	$ 3.19	$ 3.46
Total intrinsic value of options exercised during the year	$ 5	$ 11	$ 3
Term of share-based compensation awards	The reload option was permitted on certain stock option awards granted prior to January 2003 at an amount equal to the number of shares of the common stock used to satisfy both the exercise price and withholding taxes due upon exercise of an option and vest either six months or one year after the grant date and are exercisable for the remaining term of the related original option. At December 31, 2012, there were no longer any options eligible for reload.
Reload grants [Member] | Minimum [Member]
Share-based compensation
Expected term of stock options (in years)			1 year
Expected volatility rate of the Company's stock	22.90%	15.70%	18.30%
Risk-free rate	0.10%	0.10%	0.20%
Reload grants [Member] | Maximum [Member]
Share-based compensation
Expected term of stock options (in years)			2 years
Expected volatility rate of the Company's stock	23.50%	17.60%	41.60%
Risk-free rate	0.17%	0.29%	0.95%