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, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	1,010,157
Number of options, Vested	304,146
Number of options, Forfeited	8,682
Number of options, Unvested	697,329
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	62,264
Number of options, Forfeited	264
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	62,612
Number of options, Forfeited	532
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	21,085
Number of options, Forfeited	1,971
Number of options, Unvested	6,540
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	11,003
Number of options, Unvested	3,666
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	10,632
Number of options, Forfeited	3,104
Number of options, Unvested	10,630
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	11,664
Number of options, Unvested	11,663
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, Vested	48,416
Number of options, Forfeited	818
Number of options, Unvested	237,929
December 14, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	43,260
Number of options, Forfeited	544
Number of options, Unvested	42,716
December 16, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	71,543
Number of options, Unvested	71,543
April 5, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	262,830
Number of options, Unvested	262,830
April 19, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	22,888
Number of options, Unvested	22,888
August 11, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	26,924
Number of options, Unvested	26,924
Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	216,804
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
Directors [Member] | December 16, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	60,084
Directors [Member] | August 11, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	26,924
Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	793,353
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
Management [Member] | December 14, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	43,260
Management [Member] | December 16, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	11,459
Management [Member] | April 5, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	262,830
Management [Member] | April 19, 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Grants	22,888