Earnings per Share (details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings per Share disclosure
Net income	$ 1,052	$ 896
Participating share-based awards - allocated income	(7)	(6)
Net income available to common shareholders -- basic	1,045	890
Net income available to common shareholders -- diluted	$ 1,045	$ 890
Weighted average shares outstanding, basic	350.9	377.7
Weighted average effects of dilutive securities, stock options and performance shares (in shares)	3.7	4.2
Weighted average shares outstanding, diluted	354.6	381.9
Net income per common share, basic	$ 2.98	$ 2.36
Net income per common share, diluted	$ 2.95	$ 2.33