Benefit Plans - Components of net periodic cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Components of net periodic cost
Service cost	$ 102	$ 104	$ 108
Interest cost	229	199	221
Expected return on plan assets	(371)	(445)	(414)
Amortization of prior service credit	(52)	(75)	(64)
Curtailment losses (gains)	0	0	2
Costs and expenses	(92)	(217)	(147)
Remeasurement of projected benefit obligation	(1,444)	(325)	835
Remeasurement of plan assets	1,560	(319)	(886)
Remeasurement (gains) losses	116	(644)	(51)
Total net (benefit) cost	$ 24	$ (861)	$ (198)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Policyholder Benefits and Claims Incurred, Net, Property, Casualty and Liability, Net investment income, Operating costs and expenses, Restructuring and related charges	Policyholder Benefits and Claims Incurred, Net, Property, Casualty and Liability, Net investment income, Operating costs and expenses, Restructuring and related charges	Policyholder Benefits and Claims Incurred, Net, Property, Casualty and Liability, Net investment income, Operating costs and expenses, Restructuring and related charges
Pension benefits
Components of net periodic cost
Service cost	$ 101	$ 103	$ 104
Interest cost	219	191	210
Expected return on plan assets	(371)	(445)	(414)
Amortization of prior service credit	(27)	(50)	(54)
Curtailment losses (gains)	0	0	10
Costs and expenses	(78)	(201)	(144)
Remeasurement of projected benefit obligation	(1,382)	(309)	813
Remeasurement of plan assets	1,560	(319)	(886)
Remeasurement (gains) losses	178	(628)	(73)
Total net (benefit) cost	100	(829)	(217)
Postretirement benefits
Components of net periodic cost
Service cost	1	1	4
Interest cost	10	8	11
Expected return on plan assets	0	0	0
Amortization of prior service credit	(25)	(25)	(10)
Curtailment losses (gains)	0	0	(8)
Costs and expenses	(14)	(16)	(3)
Remeasurement of projected benefit obligation	(62)	(16)	22
Remeasurement of plan assets	0	0	0
Remeasurement (gains) losses	(62)	(16)	22
Total net (benefit) cost	$ (76)	$ (32)	$ 19