Benefit Plans - Components of net cost (benefit) for pension and other postretirement plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Costs and expenses	$ 7	$ (35)	$ 20	$ (87)
Remeasurement (gains) losses	(40)	259	(93)	12
Total net (benefit) cost	(33)	224	(73)	(75)
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	32	28	65	57
Interest cost	58	52	118	98
Expected return on plan assets	(79)	(100)	(156)	(210)
Amortization of prior service credit	0	(12)	0	(25)
Costs and expenses	11	(32)	27	(80)
Remeasurement of projected benefit obligation	(68)	(421)	55	(1,173)
Remeasurement of plan assets	30	699	(150)	1,228
Remeasurement (gains) losses	(38)	278	(95)	55
Total net (benefit) cost	(27)	246	(68)	(25)
Postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	0	1
Interest cost	2	2	5	4
Amortization of prior service credit	(6)	(6)	(12)	(12)
Costs and expenses	(4)	(3)	(7)	(7)
Remeasurement of projected benefit obligation	(2)	(19)	2	(43)
Remeasurement of plan assets	0	0	0	0
Remeasurement (gains) losses	(2)	(19)	2	(43)
Total net (benefit) cost	$ (6)	$ (22)	$ (5)	$ (50)