Leases (Components Of Lease Expense) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Leases [Abstract]
Depreciation of finance lease ROU assets	$ 10	$ 8	$ 20	$ 16
Interest on finance lease liabilities	1	1	2	2
Operating lease cost	6	6	13	13
Variable lease cost	1	1	1	1
Sublease income	(1)	(1)	(1)	(1)
Total lease cost	$ 17	$ 16	$ 33	$ 31