Significant Accounting Policies (Impacts Of Adoption Of ASU On Condensed Consolidated Statements Of Financial Position) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 97	$ 89
Finance lease assets, within property and equipment, net		195
Total right-of-use assets		86
Other assets	73	5,129	$ 87
Total assets	5,322		5,023
Current portion of long-term lease liability	20	120
Long-term lease liability	111	31
Current finance lease liability, within Current portion of long-term debt		60
Long-term finance lease liability, within Long-term debt		225
Total lease liability		60
Accrued liabilities, Other		155
Other long-term obligations, primarily self-insured claims	$ 164	2,925	182
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets			89
Finance lease assets, within property and equipment, net			89
Total right-of-use assets			87
Other assets			5,023
Long-term lease liability			31
Current finance lease liability, within Current portion of long-term debt			60
Long-term finance lease liability, within Long-term debt			90
Total lease liability			61
Accrued liabilities, Other			182
Other long-term obligations, primarily self-insured claims			$ 2,818
Accounting Standards Update 2016-02 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finance lease assets, within property and equipment, net		107
Other assets		106
Current portion of long-term lease liability		120
Long-term finance lease liability, within Long-term debt		135
Total lease liability		(1)
Accrued liabilities, Other		(28)
Other long-term obligations, primarily self-insured claims		$ 106