ASC 606 Adoption And Revenue Recognition (Schedule Of Prior Period Impact Of New Accounting Pronouncement) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 723	$ 787	$ 819
Contract acquisition costs	107	87
Other current assets	60	68	64
Property, plant and equipment, net	14,187	14,392	14,377
Other assets	265	224	97
Other current liabilities	303	335	330
Other liabilities	281	308	317
Deferred income taxes	1,109	1,190	1,139
Accumulated deficit	(2,752)	$ (2,109)	(2,263)
Impact Of Adoption Of ACS 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	44		(32)
Contract acquisition costs	(107)		87
Other current assets	(4)		4
Property, plant and equipment, net	(56)		15
Other assets	(117)		127
Other current liabilities	(6)		5
Other liabilities	10		(9)
Deferred income taxes	(57)		51
Accumulated deficit	(184)		$ 154
Amounts Excluding Adoption of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	767
Other current assets	56
Property, plant and equipment, net	14,131
Other assets	148
Other current liabilities	297
Other liabilities	291
Deferred income taxes	1,052
Accumulated deficit	$ (2,936)