Earnings per Share (details) (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings per Share disclosure
Net income (loss)	$ (364)	$ 670	$ 475	$ 1,317
Preferred stock dividends			(1)	(1)
Participating share-based awards - allocated income	(2)	(5)	(4)	(10)
Net income (loss) available to common shareholders -- basic	(366)	665	470	1,306
Effect of dilutive securities, convertible preferred stock			1	1
Net income (loss) available to common shareholders -- diluted	(366)	665	471	1,307
Weighted average shares outstanding, basic	418.6	484.5	423.3	496.3
Weighted average effects of dilutive securities, stock options and performance shares (in shares)		4.5	4.4	4.5
Weighted average effects of dilutive securities, convertible preferred stock (in shares)		1.8	1.4	1.8
Weighted average shares outstanding, diluted	418.6	490.8	429.1	502.6
Net income (loss) per common share, basic	$ (0.88)	$ 1.37	$ 1.11	$ 2.63
Net income (loss) per common share, diluted	$ (0.88)	$ 1.35	$ 1.10	$ 2.60
Amount of allocation of undistributed loss excluded from earnings per share	$ 4.6
Number of stock options and performance shares excluded from the calculation of net loss per share on a diluted basis (in shares)	4.6
Number of shares of convertible preferred stock excluded from the calculation of net loss per share on a diluted basis (converted into common shares)	1.2