Leases (Effect Of The Adoption Of ASC 842) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets	$ 455		$ 455		$ 470	$ 265
Other current liabilities	400		400		426	394
Other liabilities	399		399		439	281
Deferred income taxes	599		599		1,113	1,109
Accumulated deficit	(8,067)		(8,067)		(2,741)	(2,752)
Operating lease liabilities	204		204
Operating right-of-use assets	198		198
Income tax expense (benefit)	(534)	$ (20)	(516)	$ (7)
Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets						265
Other current liabilities						394
Other liabilities						281
Deferred income taxes						1,109
Accumulated deficit						$ (2,752)
Other Current Liabilities [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Current operating lease liabilities	44		44
Other Noncurrent Liabilities [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Noncurrent operating lease liabilities	160		160
Accounting Standards Update 2016-02 [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets					205
Other current liabilities					32
Other liabilities					158
Deferred income taxes					4
Accumulated deficit					11
Operating right-of-use assets	$ 205		$ 205
Current operating lease liabilities					46
Noncurrent operating lease liabilities					168
Accounting Standards Update 2016-02 [Member] | Accumulated Deficit [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred gain on sale of property					15
Tax effect on the gain of sale of property					4
Accounting Standards Update 2016-02 [Member] | Other Current Liabilities [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred gain on sale of property					14
Accounting Standards Update 2016-02 [Member] | Other Noncurrent Liabilities [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred rent					9
Deferred gain on sale of property					1
Accounting Standards Update 2016-02 [Member] | Deferred Tax Liabilities Noncurrent [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred gain on sale of property					$ 15