Earnings Per Share and Equity - Schedule of Earnings per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 629	$ 993	$ 1,959	$ 1,604
Average common shares outstanding — basic	913	861	879	860
Potentially dilutive effect of stock options, performance share awards and restricted stock	2	2	4	3
Average common shares outstanding — diluted	915	863	883	863