Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - Pension Plan [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 53	$ 54	$ 107	$ 107
Interest cost	31	30	60	58
Expected return on plan assets	(86)	(95)	(165)	(182)
Amortization:
Net loss	50	47	95	90
Prior service cost	0	1	0	1
Net periodic pension cost	$ 48	$ 37	$ 97	$ 74