Benefit Plans - Schedule of Components of Net Cost (Benefit) for Pension and Other Postretirement Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Costs and expenses	$ 16	$ 13
Remeasurement (gains) losses	(2)	(53)
Total net cost (benefit)	14	(40)
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	33	33
Interest cost	58	60
Expected return on plan assets	(77)	(77)
Amortization of prior service credit	0	0
Costs and expenses	14	16
Remeasurement of projected benefit obligation	(25)	123
Remeasurement of plan assets	25	(180)
Remeasurement (gains) losses	0	(57)
Total net cost (benefit)	14	(41)
Postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	2	3
Amortization of prior service credit	0	(6)
Costs and expenses	2	(3)
Remeasurement of projected benefit obligation	(2)	4
Remeasurement of plan assets	0	0
Remeasurement (gains) losses	(2)	4
Total net cost (benefit)	$ 0	$ 1