Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Results (Unaudited)
Revenues	$ 792	$ 784	$ 758	$ 754	$ 748	$ 816	$ 790	$ 664	$ 3,088	$ 3,018	$ 2,973
Operating loss	(74)	(607)	(27)	(13)	(25)	(305)	(917)	(4)	(721)	(1,251)	(2,505)
Net loss	(55)	(825)	(206)	(171)	(243)	(409)	(1,139)	(212)	(1,257)	(2,003)	(3,097)
Net loss attributable to controlling interest	$ (51)	$ (825)	$ (208)	$ (171)	$ (242)	$ (409)	$ (1,135)	$ (210)	$ (1,255)	$ (1,996)	$ (3,127)
Per share earnings (loss) from continuing operations
Basic (in dollars per share)	$ (0.08)	$ (1.35)	$ (0.34)	$ (0.28)	$ (0.48)	$ (0.88)	$ (2.46)	$ (0.48)	$ (2.05)	$ (4.27)	$ (8.00)
Diluted (in dollars per share)	$ (0.08)	$ (1.35)	$ (0.34)	$ (0.28)	$ (0.48)	$ (0.88)	$ (2.46)	$ (0.48)	$ (2.05)	$ (4.27)	$ (8.00)
Weighted-average shares outstanding
Basic (in shares)	613	613	612	611	506	463	462	438	612	468	391
Diluted (in shares)	613	613	612	611	506	463	462	438	612	468	391