Schedule I - Condensed Financial Information of Parent (Statement of Comprehensive Income Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Foreign currency translation adjustments, income tax benefit (expense)	$ (2)	$ (17)	$ (1)
Foreign currency, reclassification to earnings, income tax benefit (expense)	0	0	0
Change in derivative fair value, income tax benefit (expense)	(27)	(10)	7
Derivative reclassification to earnings, income tax benefit (expense)	24	1	8
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Tax	(1)	1	6
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	(1)	(6)	(106)
Pension, amortization of net actuarial loss, income tax benefit (expense)	2	135	3
Parent Company
Condensed Financial Statements, Captions [Line Items]
Foreign currency translation adjustments, income tax benefit (expense)	2	11	1
Foreign currency, reclassification to earnings, income tax benefit (expense)	0	0	0
Change in derivative fair value, income tax benefit (expense)	16	13	(5)
Derivative reclassification to earnings, income tax benefit (expense)	(13)	1	1
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Tax	(1)	(1)	(5)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax	(1)	6	10
Pension, amortization of net actuarial loss, income tax benefit (expense)	$ (2)	$ (126)	$ 2