Employee Stock And Incentive Plan (Summary Of Compensation Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within opertions and maintenance expense	$ 23,519	$ 21,758	$ 19,569
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within opertions and maintenance expense	650	451	480
Income tax benefit	162	140	136
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within opertions and maintenance expense	6,942	7,950	7,150
Income tax benefit	1,741	1,997	2,038
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within opertions and maintenance expense	2,877	2,927	3,360
Income tax benefit	722	736	953
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within opertions and maintenance expense	43	50	130
Income tax benefit	12	15	37
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within opertions and maintenance expense	810	715	700
Income tax benefit	$ 228	$ 207	$ 202