Earnings Per Share and Equity - Schedule of Earnings per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 638	$ 522	$ 1,331	$ 612
Average common shares outstanding — basic	863	860	862	860
Potentially dilutive effect of stock options, performance share awards and restricted stock	3	4	4	3
Average common shares outstanding — diluted	866	864	866	863