Earnings Per Share and Equity - Schedule of Earnings per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income attributable to common shareholders									$ 2,269	$ 1,623	$ 1,719
Weighted average common shares outstanding—basic	921	913	863	862	861	861	860	858	890	860	856
Assumed exercise and/or distributions of stock-based awards									3	4	4
Weighted average common shares outstanding—diluted	924	915	866	867	868	863	864	861	893	864	860