Benefit Plans (Components of net periodic cost (benefit)) (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 15	$ 20
Expected return on plan assets	(38)	(39)
Amortization of net actuarial (gain) loss	12	11
Settlement loss	0	1
Total net periodic pension cost (benefit)	$ (11)	$ (7)