Revenue From Contracts With Customers (Schedule Of Disaggregation Of Revenue) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 45,988,583	$ 51,554,650	$ 102,045,861	$ 112,348,132
Variance percent	(10.70%)		(9.20%)
Energy Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 43,200,000	47,200,000	$ 96,600,000	104,000,000
Variance percent	(8.50%)		(7.10%)
Retail Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 41,900,000	45,300,000	$ 94,000,000	98,700,000
Variance percent	(7.50%)		(4.80%)
Wholesale Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 1,300,000	1,400,000	$ 2,600,000	2,900,000
Variance percent	(7.10%)		(10.30%)
Economy [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	500,000	$ 0	2,400,000
Variance percent	(100.00%)		(100.00%)
Miscellaneous Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 2,800,000	4,300,000	$ 5,400,000	8,300,000
Variance percent	(34.90%)		(34.90%)
Wheeling [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 2,200,000	2,100,000	$ 4,200,000	4,000,000
Variance percent	4.80%		5.00%
Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	1,700,000	$ 0	3,300,000
Variance percent	(100.00%)		(100.00%)
Other Miscellaneous [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 600,000	500,000	$ 1,200,000	1,000,000
Variance percent	20.00%		20.00%
Base Rate Sales Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 29,000,000	29,400,000	$ 62,400,000	64,500,000
Variance percent	(1.40%)		(3.30%)
Base Rate Sales Revenue [Member] | Energy Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 28,400,000	28,900,000	$ 61,200,000	63,500,000
Variance percent	(1.70%)		(3.60%)
Base Rate Sales Revenue [Member] | Retail Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 27,900,000	28,300,000	$ 60,200,000	62,200,000
Variance percent	(1.40%)		(3.20%)
Base Rate Sales Revenue [Member] | Wholesale Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 500,000	500,000	$ 1,000,000	1,100,000
Variance percent	0.00%		(9.10%)
Base Rate Sales Revenue [Member] | Economy [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	100,000	$ 0	200,000
Variance percent	(100.00%)		(100.00%)
Base Rate Sales Revenue [Member] | Miscellaneous Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 600,000	500,000	$ 1,200,000	1,000,000
Variance percent	20.00%		20.00%
Base Rate Sales Revenue [Member] | Wheeling [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	0	$ 0	0
Variance percent	0.00%		0.00%
Base Rate Sales Revenue [Member] | Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	0	$ 0	0
Variance percent	0.00%		0.00%
Base Rate Sales Revenue [Member] | Other Miscellaneous [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 600,000	500,000	$ 1,200,000	1,000,000
Variance percent	20.00%		20.00%
Fuel And Purchased Power Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 17,000,000	22,100,000	$ 39,600,000	47,800,000
Variance percent	(23.10%)		(17.20%)
Fuel And Purchased Power Revenue [Member] | Energy Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 14,800,000	18,300,000	$ 35,400,000	40,500,000
Variance percent	(19.10%)		(12.60%)
Fuel And Purchased Power Revenue [Member] | Retail Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 14,000,000	17,000,000	$ 33,800,000	36,500,000
Variance percent	(17.60%)		(7.40%)
Fuel And Purchased Power Revenue [Member] | Wholesale Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 800,000	900,000	$ 1,600,000	1,800,000
Variance percent	(11.10%)		(11.10%)
Fuel And Purchased Power Revenue [Member] | Economy [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	400,000	$ 0	2,200,000
Variance percent	(100.00%)		(100.00%)
Fuel And Purchased Power Revenue [Member] | Miscellaneous Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 2,200,000	3,800,000	$ 4,200,000	7,300,000
Variance percent	(42.10%)		(42.50%)
Fuel And Purchased Power Revenue [Member] | Wheeling [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 2,200,000	2,100,000	$ 4,200,000	4,000,000
Variance percent	4.80%		5.00%
Fuel And Purchased Power Revenue [Member] | Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	1,700,000	$ 0	3,300,000
Variance percent	(100.00%)		(100.00%)
Fuel And Purchased Power Revenue [Member] | Other Miscellaneous [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0	$ 0
Variance percent	0.00%		0.00%