Earnings per Share (details) (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings per Share disclosure
Net income	$ 333	$ 1,005	$ 808	$ 2,322
Preferred stock dividends		(1)	(1)	(2)
Participating share-based awards - allocated income	(2)	(8)	(6)	(18)
Net income available to common shareholders -- basic	331	996	801	2,302
Effect of dilutive securities, participating share-based awards - re-allocated income		1		1
Effect of dilutive securities, convertible preferred stock		1	1	2
Net income available to common shareholders -- diluted	$ 331	$ 998	$ 802	$ 2,305
Weighted average shares outstanding, basic	415.0	465.9	420.4	486.1
Weighted average effects of dilutive securities, stock options and performance shares (in shares)	3.5	4.4	4.3	4.4
Weighted average effects of dilutive securities, convertible preferred stock (in shares)		1.7	0.9	1.8
Weighted average shares outstanding, diluted	418.5	472.0	425.6	492.3
Net income per common share, basic	$ 0.80	$ 2.14	$ 1.90	$ 4.73
Net income per common share, diluted	$ 0.79	$ 2.11	$ 1.88	$ 4.68