Benefit Plans (Components of net periodic cost (benefit)) (Details) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0
Interest cost on projected benefit obligation	100	93	103
Expected return on plan assets	(142)	(159)	(154)
Amortization of net actuarial (gain) loss	39	37	35
Settlement loss	0	6	9
Total non-service cost (benefit)	(3)	(23)	(7)
Total net periodic pension cost (benefit)	$ (3)	$ (23)	$ (7)