Earnings Per Share and Equity - Schedule of Earnings per Share (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 993	$ 738	$ 1,604	$ 1,224
Average common shares outstanding — basic	861	857	860	856
Potentially dilutive effect of stock options, performance share awards and restricted stock	2	3	3	4
Average common shares outstanding — diluted	863	860	863	860