Stock-Based Compensation (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock option activity [Rollforward]
Exercised (in shares)	(1,265,231)	(837,096)
Stock Option [Member]
Assumptions used to value stock option awards [Abstract]
Expected term (in years)	5 years 8 months	5 years 8 months	5 years 7 months
Expected volatility (in hundredths)	37.00%	36.20%	35.40%
Risk-free rate (in hundredths)	0.90%	2.20%	2.60%
Expected dividend yield (in hundredths)	1.20%	1.10%	1.10%
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 31.98	$ 30.17	$ 25.05
Stock option activity [Rollforward]
Outstanding, beginning balance (in shares)	6,365,816
Granted (in shares)	1,225,827
Exercised (in shares)	(1,265,231)
Forfeited (in shares)	(120,626)
Outstanding, ending balance (in shares)	6,205,786	6,365,816
Exercisable (in shares)	4,164,438
Stock option activity, additional disclosures [Abstract]
Weighted average exercise price per share outstanding, beginning balance (in dollars per share)	$ 59.47
Weighted average exercise price per share granted (in dollars per share)	$ 101.50
Weighted average exercise price per share exercised (in dollars per share)	$ 43.84
Weighted average exercise price per share forfeited (in dollars per share)	$ 93.95
Weighted average exercise price per share outstanding, ending balance (in dollars per share)	$ 70.27	$ 59.47
Weighted average exercise price per exercisable share (in dollars per share)	$ 58.34
Weighted average remaining contractual term of shares outstanding (in years)	6 years 2 months
Aggregate intrinsic value of shares outstanding	$ 196
Weighted average remaining contractual term, exercisable shares (in years)	5 years 1 month
Aggregate intrinsic value, exercisable shares	181
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Minimum term to maturity on US Treasuries used to determine the risk free rate assumption in valuing stock options	5 years
Maximum term to maturity on US Treasuries used to determine the risk free rate assumption in valuing stock options	7 years
The period ended, prior to the date of grant, over which an average of daily stock prices is computed in determining the dividend yield	3 years
Duration of Dividends	1 year
Total intrinsic value of options exercised	72	40	68
Unrecognized compensation cost related to nonvested awards	36
The weighted-average period over which unrecognized compensation cost is to be recognized (in years)	1 year 5 months
Restricted Stock [Member]
Restricted Stock Awards Activity [Roll Forward]
Outstanding, beginning balance (in shares)	979,257
Awarded (in shares)	481,858
Vested (in shares)	(472,691)
Forfeited (in shares)	(55,193)
Outstanding, ending balance (in shares)	933,231	979,257
Restricted stock awards, shares subject to service conditions, additional disclosures [Abstract]
Weighted average award date fair value, beginning of period (in dollars per share)	$ 74.87
Weighted average award date fair value, shares awarded (in dollars per share)	$ 101.50	$ 90.32	$ 75.07
Weighted average award date fair value, shares vested (in dollars per share)	$ 64.63
Weighted average award date fair value, shares forfeited (in dollars per share)	$ 92.03
Weighted average award date fair value, end of period (in dollars per share)	$ 92.79	$ 74.87
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Unrecognized compensation cost related to nonvested awards	45
The weighted-average period over which unrecognized compensation cost is to be recognized (in years)	1 year 5 months
Weighted average award date fair value, shares awarded (in dollars per share)	$ 101.50	$ 90.32	$ 75.07
Total fair value of vested restricted stock	$ 47	$ 57	$ 43
Stock Option And Restricted Stock Plan 1992 [Member]
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Maximum number of shares of common stock authorized for issuance prior to April, 26 2011 (in shares)	24,000,000
Maximum number of shares of common stock authorized for issuance After April 26, 2011 (in shares)	31,000,000
Number of shares of common stock reserved for issuance (in shares)	12,180,343
Shares of common stock available for future grants and awards (in shares)	7,009,795
Expiration period (in years)	10 years
Stock option vesting period	3 years
Percentage of restricted stock awards that time-vest one year from date of grant (in hundredths)	20.00%
Additional percentage of restricted stock awards that time-vest two years from date of grant (in hundredths)	30.00%
Remaining percentage of restricted stock awards that time-vest three years from date of grant (in hundredths)	50.00%
Stock Plan for Non-Employee Directors 2005 [Member]
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Maximum number of shares of common stock authorized for issuance After April 26, 2011 (in shares)	800,000
Number of shares of common stock reserved for issuance (in shares)	696,178
Shares of common stock available for future grants and awards (in shares)	476,873
Expiration period (in years)	10 years
Stock option vesting period	1 year
The maximum number of stock options authorized for annual and discretionary grants per non-employee director (in shares)	11,200
The number of stock options authorized for annual grants per non-employee director (in shares)	2,800
The maximum number of shares of restricted stock authorized for annual and discretionary grants per non-employee director (in shares)	4,800
The number of shares of restricted stock authorized for annual grants per non-employee director (in shares)	1,200
Nonqualified Stock Option Plan for Non-Employee Directors 1988 [Member]
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Expiration period (in years)	10 years
Stock option vesting period	1 year
The number of stock options authorized for annual grants per non-employee director (in shares)	5,000
The number of stock options granted during the first calendar year of service (in shares)	10,000