Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment, VIEs	$ 21,797	$ 21,548
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	500,000,000	500,000,000
Common stock, issued	309,670,932	309,600,439
Common stock, outstanding	309,069,291	308,993,149
Variable Interest Entity, Primary Beneficiary [Member]
Property, Plant and Equipment, VIEs	$ 1,101	$ 1,144