Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other income (expense)
Interest expense, net									$ (747)	$ (488)	$ (322)
Total other expense									(822)	(633)	(648)
Net loss attributable to common stockholders	$ 127	$ (289)	$ (285)	$ 54	$ 110	$ (101)	$ (298)	$ (321)	(393)	(610)	(975)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
General and administrative expense									7	6	0
Other income (expense)
Interest expense, net									(118)	(104)	(93)
Interest expense, net—affiliates									0	(7)	(9)
Interest income—affiliates									0	24	34
Equity loss of affiliates									(268)	(517)	(907)
Total other expense									(386)	(604)	(975)
Net loss attributable to common stockholders									$ (393)	$ (610)	$ (975)