Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 21
Interest cost on projected benefit obligation	33	24
Expected return on plan assets	(37)	(49)
Total pension benefit cost / (income)	9	(4)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	4
Interest cost on projected benefit obligation	8	6
Amortization of prior service benefit	(5)	(3)
Remeasurement gains	20
Net periodic benefit cost / (income)	$ 25	$ 7