Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - Pension Plan [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 65	$ 54
Interest cost	17	29
Expected return on plan assets	(86)	(79)
Amortization:
Net loss	65	45
Prior service cost	0	0
Net periodic pension cost	$ 61	$ 49