Income per Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share [Abstract]
Income from continuing operations	$ 393	$ 298	$ 810	$ 753
Discontinued operations		698		1,239
Net income	$ 393	$ 996	$ 810	$ 1,992
Weighted average common shares outstanding, basic	706	713	705	712
Effect of dilutive securities	3	4	4	4
Weighted average common shares outstanding, diluted	709	717	709	716
Basic:
Income from continuing operations, per basic share	$ 0.56	$ 0.42	$ 1.15	$ 1.06
Discontinued operations, per basic share		$ 0.98		$ 1.74
Net income, per basic share	$ 0.56	$ 1.40	$ 1.15	$ 2.80
Diluted:
Income from continuing operations, per diluted share	$ 0.56	$ 0.42	$ 1.14	$ 1.05
Discontinued operations, per diluted share		$ 0.97		$ 1.73
Net income, per diluted share	$ 0.56	$ 1.39	$ 1.14	$ 2.78
Antidilutive securities excluded from computation of earnings per share	10	5	9	6