Debt And Credit Agreements (Schedule Of Borrowings Under Credit Agreement At Various Indebtedness To Adjusted EBITDA Levels) (Details)	12 Months Ended
	Dec. 31, 2020
Indebtedness To Adjusted Ebitda Ratio Greater Than Three Point Five But Less Than Or Equal To Four [Member]
Line of Credit Facility [Line Items]
Indebtedness To Adjusted Ebitda Ratio Greater Than Three Point Five But Less Than Or Equal To Four [Member]	20000.00%
Line of Credit Facility, Commitment Fee Amount	40
Indebtedness-To-Adjusted EBITDA Ratio Greater Than 2.0x But Less Than Or Equal To 3.0x [Member]
Line of Credit Facility [Line Items]
Indebtedness To Adjusted Ebitda Ratio Greater Than Three Point Five But Less Than Or Equal To Four [Member]	17500.00%
Line of Credit Facility, Commitment Fee Amount	30
Indebtedness-To-Adjusted EBITDA Ratio Greater Than 1.0x But Less Than Or Equal To 2.0x [Member]
Line of Credit Facility [Line Items]
Indebtedness To Adjusted Ebitda Ratio Greater Than Three Point Five But Less Than Or Equal To Four [Member]	16250.00%
Line of Credit Facility, Commitment Fee Amount	25
Indebtedness To Adjusted Ebitda Ratio Greater Than Three But Less Than Or Equal To Three Point Five [Member]
Line of Credit Facility [Line Items]
Indebtedness To Adjusted Ebitda Ratio Greater Than Three Point Five But Less Than Or Equal To Four [Member]	18750.00%
Line of Credit Facility, Commitment Fee Amount	35
Indebtedness To Adjusted Ebitda Ratio Less Than Or Equal To One [Member]
Line of Credit Facility [Line Items]
Indebtedness To Adjusted Ebitda Ratio Greater Than Three Point Five But Less Than Or Equal To Four [Member]	15000.00%
Line of Credit Facility, Commitment Fee Amount	20