Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Jun. 30, 2022	Apr. 30, 2021	Jun. 30, 2022
Successor [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 13	$ 20		$ 41
Interest cost on projected benefit obligation		18	25		49
Expected return on plan assets		(31)	(50)		(99)
Net periodic (benefit) cost			(5)		(9)
Successor [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		3	3		7
Interest cost on projected benefit obligation		5	8		14
Amortization of prior service (benefit)		(1)	(3)		(6)
Remeasurement gains		13	(96)		(150)
Net periodic (benefit) cost		$ 20	$ (88)		$ (135)
Predecessor [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8			$ 32
Interest cost on projected benefit obligation	8			31
Expected return on plan assets	(16)			(61)
Amortization of unrecognized loss	6			24
Net periodic (benefit) cost	6			26
Predecessor [Member] | OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2			7
Interest cost on projected benefit obligation	2			9
Amortization of prior service (benefit)	(3)			(10)
Amortization of unrecognized loss	2			5
Net periodic (benefit) cost	$ 3			$ 11