Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
Net income, as reported	$ 283	$ 267	$ 790	$ 806
Less: Net income attributable to participating securities	(1)	(1)	(2)	(2)
Net income available to common shareholders	$ 282	$ 266	$ 788	$ 804
Denominator:
Basic EPS- weighted average shares	130.07	136.74	130.25	141.08
Effect of dilutive securities:
Stock Options and SARS	0.28	0.28	0.30	0.23
Diluted EPS- adjusted weighted average shares and assumed conversions	130.35	137.02	130.55	141.31
Earning Per Share:
Basic	$ 2.17	$ 1.94	$ 6.05	$ 5.70
Diluted	$ 2.16	$ 1.94	$ 6.03	$ 5.69
Earnings Per Share (Textual) [Abstract]
Common stock excluded from the diluted earnings per share	0		0