Fair Value Measurements (Schedule Of The Carrying Amount And Estimated Fair Value Of The Company's Financial Instruments That Are Recorded At Fair Value On A Recurring Basis) (Details) - Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Carrying Value [Member]
Financial Assets:
Deferred compensation trust	$ 13	$ 13
Derivative asset, Noncurrent		30
Total financial assets	19	496
Derivative contracts	1	4
Total financial liabilities	1	4
Carrying Value [Member] | Investment In Frontdoor, Inc. [Member]
Financial Assets:
Investments		445
Carrying Value [Member] | Investment In Marketable Securities [Member]
Financial Assets:
Investments		8
Carrying Value [Member] | Fuel Swap Contracts [Member]
Financial Assets:
Derivative asset, Noncurrent	1
Carrying Value [Member] | Interest Rate Swap Contracts [Member]
Financial Assets:
Derivative asset, Noncurrent	5
Estimated Fair Value [Member] | Quoted Price In Active Markets (Level 1) [Member]
Financial Assets:
Deferred compensation trust	13	13
Total financial assets	13	21
Estimated Fair Value [Member] | Quoted Price In Active Markets (Level 1) [Member] | Investment In Marketable Securities [Member]
Financial Assets:
Investments		8
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Derivative asset, Noncurrent		30
Total financial assets	5	475
Derivative contracts	1
Total financial liabilities	1
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Investment In Frontdoor, Inc. [Member]
Financial Assets:
Investments		445
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Swap Contracts [Member]
Financial Assets:
Derivative asset, Noncurrent	5
Estimated Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial Assets:
Total financial assets	1
Derivative contracts		4
Total financial liabilities		$ 4
Estimated Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fuel Swap Contracts [Member]
Financial Assets:
Derivative asset, Noncurrent	$ 1