Stock Options and Other Share-Based Compensation (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Stock Option
Expected term in years	6.2	6.1	6.0
Volatility	31.00%	30.80%	30.20%
Risk-free interest rate based on zero coupon U.S. treasury note	2.60%	2.90%	2.10%
Dividend yield	3.60%	3.90%	3.20%
Weighted-average fair value per option granted	$ 21.24	$ 16.28	$ 15.36
Restored Options
Expected term in years	1.2	1.2	1.2
Volatility	20.60%	38.90%	45.00%
Risk-free interest rate based on zero coupon U.S. treasury note	0.70%	0.60%	1.10%
Dividend yield	3.40%	3.80%	3.50%
Weighted-average fair value per option granted	$ 7.55	$ 12.91	$ 12.38
Summary of option activity
Shares Outstanding at January 1, 2011	74,852
Weighted-Average Exercise Price of shares Outstanding at January 1, 2011	$ 67.04
Shares Granted	14,260
Weighted-Average Exercise Price Granted	$ 94.46
Shares Exercised	(15,844)
Weighted-Average Exercise Price Exercised	$ 60.20
Shares Restored	33
Weighted-Average Exercise Price Restored	$ 103.96
Shares Forfeited	(953)
Weighted-Average Exercise Price Forfeited	$ 85.79
Shares Outstanding at December 31, 2011	72,348	74,852
Weighted-Average Exercise Price of shares Outstanding at December 31, 2011	$ 73.71	$ 67.04
Weighted-Remaining Contractual Term Outstanding at December 31, 2011	6.4
Aggregate Intrinsic Value Outstanding at December 31, 2011	$ 2,365
Shares Exercisable at December 31, 2011	45,494
Weighted-Average Exercise Price of shares Exercisable at December 31, 2011	$ 67.84
Weighted-Remaining Contractual Term of shares Exercisable at December 31, 2011	5.3
Aggregate Intrinsic Value of shares Exercisable at December 31, 2011	$ 1,755