Share-based Compensation and Employee Benefits - Components of Funded Status (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Non-current benefit asset	$ 0	$ 0
Current benefit liability	0	0
Non-current benefit liability	(620)	(702)
Funded status - net liability at December 31,	(620)	(702)
OPEB
Defined Benefit Plan Disclosure [Line Items]
Non-current benefit asset	231	190
Current benefit liability	(18)	(13)
Non-current benefit liability	(213)	(210)
Funded status - net liability at December 31,	0	(33)
OPEB | Other Affiliates [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-current benefit asset	$ 39	$ 32