Pension, Savings, and Other Employee Benefits - Schedule Of Components Of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 24	$ 30	$ 28
Expected return on plan assets	(26)	(37)	(33)
Actuarial (gain) loss	13	10	12
Net periodic benefit cost	11	3	7
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	1
Expected return on plan assets	(1)	(1)	(1)
Actuarial (gain) loss	0	0	0
Net periodic benefit cost	$ 0	$ 0	$ 0