ASC 606 Adoption And Revenue Recognition (Schedule Of Prior Period Impact Of New Accounting Pronouncement) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 744	$ 787	$ 819
Contract acquisition costs	102	87
Other current assets	103	68	64
Property, plant and equipment, net	14,268	14,392	14,377
Other assets	233	224	97
Other current liabilities	324	335	330
Other liabilities	296	308	317
Deferred income taxes	1,204	1,190	1,139
Accumulated deficit	(2,533)	(2,109)	$ (2,263)
Accounting Standards Update 2014-09 [Member] | Impact Of Adoption Of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	38	(32)
Contract acquisition costs	(102)	87
Other current assets	4	4
Property, plant and equipment, net	(47)	15
Other assets	(132)	127
Other current liabilities	(4)	5
Other liabilities	3	(9)
Deferred income taxes	(52)	51
Accumulated deficit	$ (181)	$ 154