Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment, VIEs	$ 22,917	$ 22,669
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	500,000,000	500,000,000
Common stock, issued	309,752,140	309,670,932
Common stock, outstanding	309,005,272	309,005,272
Variable Interest Entity, Primary Beneficiary [Member]
Property, Plant and Equipment, VIEs	$ 1,276	$ 1,303