Stock-Based Compensation And Stock Repurchases (Schedule Of Restricted Stock Units Issued And Vested) (Details) - Restricted Stock Units (RSUs) [Member]	9 Months Ended
	Sep. 30, 2020 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	582,712
Number of options, Vested	225,965
Number of options, Forfeited	6,521
Number of options, Unvested	350,226
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	62,262
Number of options, Forfeited	266
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	5,108
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	54,196
Number of options, Forfeited	532
Number of options, Unvested	8,416
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	7,394
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, Vested	14,553
Number of options, Forfeited	1,170
Number of options, Unvested	13,873
April 13, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	14,669
Number of options, Vested	7,336
Number of options, Unvested	7,333
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, Vested	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, Vested	5,316
Number of options, Forfeited	3,104
Number of options, Unvested	15,946
March 14, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	23,327
Number of options, Vested	5,832
Number of options, Unvested	17,495
May 7, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	11,565
Number of options, Vested	11,565
March 10, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	287,163
Number of options, Unvested	287,163
Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	129,796
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
Directors [Member] | May 7, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	11,565
Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	452,916
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
Management [Member] | March 10, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	287,163