Stock-Based Compensation (Summary Of Compensation Costs) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within operations and maintenance expense				$ 30
Income tax benefit	2	110	98	433
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within operations and maintenance expense	1,220	1,044	3,689	2,723
Income tax benefit	495	424	1,506	1,109
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within operations and maintenance expense	295	214	827	612
Income tax benefit	122	88	342	252
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation within operations and maintenance expense	92	92	629	678
Income tax benefit	$ 38	$ 38	$ 261	$ 281