Pension, Savings, and Other Employee Benefits - Funded (Unfunded) Status of Plan (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 37	$ 37
Funded status of the plans	3	(10)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	43	39
Funded status of the plans	(23)	(22)
Qualified pension | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Funded status of the plans	$ 41	$ 27