Leases (Effect Of The Adoption Of ASC 842) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 02, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets	$ 468	$ 470	$ 265
Other current liabilities	375	426	394
Other liabilities	412	439	281
Deferred income taxes	462	1,113	1,109
Accumulated deficit	(8,573)	(2,741)	(2,752)
Operating right-of-use assets	204
Current operating lease liabilities	44
Noncurrent operating lease liabilities	$ 167
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]
Deferred gain on sale of property		14
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 Noncurrent Liabilities [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred rent		9
Accounting Standards Update 2016-02 [Member] | Other Noncurrent Liabilities [Member] | Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
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