Benefit Plans - Components of net cost (benefit) for pension and other postretirement plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Components of net periodic cost
Costs and expenses	$ (52)	$ (62)
Remeasurement (gains) losses	(247)	(310)
Pension net benefit	(299)	(372)
Pension benefits
Components of net periodic cost
Service cost	29	26
Interest cost	46	46
Expected return on plan assets	(110)	(117)
Amortization of prior service credit	(13)	(13)
Costs and expenses	(48)	(58)
Remeasurement of projected benefit obligation	(752)	(512)
Remeasurement of plan assets	529	221
Remeasurement (gains) losses	(223)	(291)
Pension net benefit	(271)	(349)
Postretirement benefits
Components of net periodic cost
Service cost	0	0
Interest cost	2	2
Amortization of prior service credit	(6)	(6)
Costs and expenses	(4)	(4)
Remeasurement of projected benefit obligation	(24)	(19)
Remeasurement of plan assets	0	0
Remeasurement (gains) losses	(24)	(19)
Pension net benefit	$ (28)	$ (23)