Employee Benefit Plans (Reconciliation of Assets Measured at Fair Value on a Recurring Basis) (Details) - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at prior measurement date	$ 11	$ 27
Sales	(12)	(18)
Total gains and other, net	1	2
Transfer of Level 3 assets to other classifications	0	0
Plan assets at measurement date	$ 0	$ 11