Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 7	$ 1,047	$ (168)	$ 124	$ 425	$ 549	$ 198	$ (318)	$ 1,009	$ 854	$ 593
Weighted Average Number of Shares Outstanding, Basic									845	838	834
Incremental Common Shares Attributable to Share-based Payment Arrangements									5	6	9
Weighted Average Number of Shares Outstanding, Diluted									850	844	843
Earnings Per Share, Basic	$ 0.01	$ 1.24	$ (0.20)	$ 0.15	$ 0.51	$ 0.66	$ 0.24	$ (0.38)	$ 1.20	$ 1.02	$ 0.71
Earnings Per Share, Diluted	$ 0.01	$ 1.23	$ (0.20)	$ 0.15	$ 0.50	$ 0.65	$ 0.23	$ (0.38)	$ 1.19	$ 1.01	$ 0.70
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									18	17	22