Leases (Effect Of The Adoption Of ASC 842) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets	$ 459		$ 459		$ 470	$ 265
Other current liabilities	386		386		426	394
Other liabilities	398		398		439	281
Deferred income taxes	580		580		1,113	1,109
Accumulated deficit	(8,411)		(8,411)		(2,741)	(2,752)
Operating lease liabilities	203		203
Operating right-of-use assets	196		196
Income tax expense (benefit)	(21)	$ (4)	(537)	$ (11)
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	$ 159		$ 159
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
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