Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Successor [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 21
Interest cost on projected benefit obligation	24
Expected return on plan assets	(49)
Net periodic benefit cost	(4)
Successor [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4
Interest cost on projected benefit obligation	6
Amortization of prior service cost (credit)	(3)
Net periodic benefit cost	$ 7
Predecessor [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 24
Interest cost on projected benefit obligation		23
Expected return on plan assets		(45)
Amortization of unrecognized loss		18
Net periodic benefit cost		20
Predecessor [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		5
Interest cost on projected benefit obligation		7
Amortization of prior service cost (credit)		(7)
Amortization of unrecognized loss		3
Net periodic benefit cost		$ 8