Leases (Components Of Lease Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Depreciation of finance lease ROU assets	$ 10	$ 9	$ 29	$ 25
Interest on finance lease liabilities	1	1	2	4
Operating lease cost	6	6	19	19
Variable lease cost		1	1	3
Sublease income	(1)	(1)	(2)	(2)
Total lease cost	$ 16	$ 17	$ 49	$ 48