Employee Benefit Plans (Reconciliation of Assets Measured at Fair Value on a Recurring Basis) (Details) - Level 3 [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at prior measurement date	$ 38	$ 31
Assets received from acquisition		9
Sales	(2)	(2)
Total gains (losses) and other, net	1
Transfer of Level 3 assets to other classifications	(9)
Plan assets at measurement date	$ 28	$ 38