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, 2020	Dec. 31, 2019
Carrying Value [Member]
Financial Assets:
Deferred compensation trust	$ 14	$ 13
Total financial assets	18	19
Total financial liabilities	72	1
Carrying Value [Member] | Cross-Currency Interest Rate Swap [Member]
Financial Assets:
Derivative contracts	15
Carrying Value [Member] | Net Investment Hedge [Member]
Financial Assets:
Derivative contracts	23
Carrying Value [Member] | Fuel Swap Contracts [Member]
Financial Assets:
Derivative asset, Noncurrent	3	1
Carrying Value [Member] | Interest Rate Swap Contract [Member]
Financial Assets:
Derivative asset, Noncurrent		5
Derivative contracts	34	1
Estimated Fair Value [Member] | Quoted Prices In Active Markets (Level 1) [Member]
Financial Assets:
Deferred compensation trust	14	13
Total financial assets	14	13
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Total financial assets		5
Total financial liabilities	72	1
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Cross-Currency Interest Rate Swap [Member]
Financial Assets:
Derivative contracts	15
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Net Investment Hedge [Member]
Financial Assets:
Derivative contracts	23
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Swap Contract [Member]
Financial Assets:
Derivative asset, Noncurrent		5
Derivative contracts	34	1
Estimated Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial Assets:
Total financial assets	3	1
Estimated Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fuel Swap Contracts [Member]
Financial Assets:
Derivative asset, Noncurrent	$ 3	$ 1