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Stock-Based Compensation And Stock Repurchases (Schedule Of Restricted Stock Units Issued And Vested) (Details) - Restricted Stock Units (RSUs) [Member]
3 Months Ended
Mar. 31, 2019
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 283,984
Number of options, Vested 138,509
Number of options, Unvested 144,026
Number of options, Forfeited 1,449
March 10, 2016 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 62,528
Number of options, Vested 55,684
Number of options, Unvested 6,844
April 11, 2016 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 5,625
Number of options, Vested 2,815
Number of options, Unvested 2,293
Number of options, Forfeited 517
March 23, 2017 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 63,144
Number of options, Vested 46,919
Number of options, Unvested 16,225
August 29, 2017 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 7,394
Number of options, Vested 3,698
Number of options, Unvested 3,696
January 2, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 29,393
Number of options, Vested 29,393
April 12, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 29,596
Number of options, Unvested 29,596
April 13, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 14,669
Number of options, Unvested 14,669
July 6, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 932
Number of options, Forfeited 932
November 7, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 23,010
Number of options, Unvested 23,010
March 13, 2019 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 24,366
Number of options, Unvested 24,366
March 14, 2019 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 23,327
Number of options, Unvested 23,327
Directors [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 118,231
Directors [Member] | March 10, 2016 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 35,147
Directors [Member] | March 23, 2017 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 30,681
Directors [Member] | January 2, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 29,393
Directors [Member] | November 7, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 23,010
Management [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 165,753
Management [Member] | March 10, 2016 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 27,381
Management [Member] | April 11, 2016 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 5,625
Management [Member] | March 23, 2017 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 32,463
Management [Member] | August 29, 2017 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 7,394
Management [Member] | April 12, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 29,596
Management [Member] | April 13, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 14,669
Management [Member] | July 6, 2018 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 932
Management [Member] | March 13, 2019 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 24,366
Management [Member] | March 14, 2019 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of options, Grants 23,327