Benefit Plans (Components of net periodic cost (benefit)) (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 15	$ 20	$ 46	$ 60
Expected return on plan assets	(38)	(38)	(115)	(116)
Amortization of net actuarial (gain) loss	12	11	35	33
Settlement loss	0	0	1	2
Total net periodic pension cost (benefit)	$ (11)	$ (7)	$ (33)	$ (21)