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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 204	$ 490	$ 267	$ 173	$ 309	$ 629	$ 638	$ 693	$ 1,134	$ 2,269	$ 1,623
Weighted average common shares outstanding—basic	925	925	924	923	921	913	863	862	924	890	860
Assumed exercise and/or distributions of stock-based awards									3	3	4
Weighted average common shares outstanding—diluted	928	927	926	925	924	915	866	867	927	893	864