Income per Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Income from continuing operations	$ 1,593	$ 1,613	$ 1,718
Discontinued operations	160	(31)	1,228
Net income	$ 1,753	$ 1,582	$ 2,946
Basic	705	706	710
Effect of dilutive securities	4	4	4
Diluted	709	710	714
Basic:
Income from continuing operations (in dollars per share)	$ 2.26	$ 2.28	$ 2.42
Discontinued operations	$ 0.23	$ (0.04)	$ 1.73
Net income (in dollars per share)	$ 2.49	$ 2.24	$ 4.15
Diluted:
Income from continuing operations (in dollars per share)	$ 2.24	$ 2.27	$ 2.41
Discontinued operations (in dollars per share)	$ 0.23	$ (0.04)	$ 1.72
Net income (in dollars per share)	$ 2.47	$ 2.23	$ 4.13
Antidilutive securities excluded from computation of earnings per share	5	10	7