Benefit Plans - Schedule of Components of Net Cost (Benefit) for Pension and Other Postretirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Costs and expenses	$ 11	$ (10)	$ 31	$ (97)
Remeasurement (gains) losses	149	79	56	91
Total net cost (benefit)	160	69	87	(6)
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	34	22	99	79
Interest cost	58	59	176	157
Expected return on plan assets	(78)	(85)	(234)	(295)
Amortization of prior service credit	0	(2)	0	(27)
Costs and expenses	14	(6)	41	(86)
Remeasurement of projected benefit obligation	(211)	(254)	(156)	(1,427)
Remeasurement of plan assets	369	335	219	1,563
Remeasurement (gains) losses	158	81	63	136
Total net cost (benefit)	172	75	104	50
Postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	1
Interest cost	3	3	8	7
Amortization of prior service credit	(6)	(7)	(18)	(19)
Costs and expenses	(3)	(4)	(10)	(11)
Remeasurement of projected benefit obligation	(9)	(2)	(7)	(45)
Remeasurement of plan assets	0	0	0	0
Remeasurement (gains) losses	(9)	(2)	(7)	(45)
Total net cost (benefit)	$ (12)	$ (6)	$ (17)	$ (56)