LONG-TERM DEBT (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended					12 Months Ended				1 Months Ended			1 Months Ended							1 Months Ended			1 Months Ended			1 Months Ended						0 Months Ended		0 Months Ended		0 Months Ended	1 Months Ended			1 Months Ended											1 Months Ended		12 Months Ended
	Dec. 31, 2012 state	Dec. 31, 2011	Feb. 07, 2011	Dec. 31, 2012 First mortgage bonds	Dec. 31, 2011 First mortgage bonds	Dec. 31, 2012 First mortgage bonds EDE	Dec. 31, 2012 First mortgage bonds EDG	Dec. 31, 2012 7.20% Series due 2016 EDE	Dec. 31, 2011 7.20% Series due 2016 EDE	Apr. 30, 2012 5.3% Pollution Control Series due 2013	Dec. 31, 2012 5.3% Pollution Control Series due 2013 EDE	Dec. 31, 2011 5.3% Pollution Control Series due 2013 EDE	Apr. 30, 2012 5.2% Pollution Control Series due 2013	Dec. 31, 2012 5.2% Pollution Control Series due 2013 EDE	Dec. 31, 2011 5.2% Pollution Control Series due 2013 EDE	Dec. 31, 2012 5.875% Series due 2037 EDE	Dec. 31, 2011 5.875% Series due 2037 EDE	Dec. 31, 2012 6.375% Series due 2018 EDE	Dec. 31, 2011 6.375% Series due 2018 EDE	May 31, 2010 4.65% Series due 2020 EDE	Dec. 31, 2012 4.65% Series due 2020 EDE	Dec. 31, 2011 4.65% Series due 2020 EDE	Aug. 31, 2010 5.20% Series due 2040 EDE	Dec. 31, 2012 5.20% Series due 2040 EDE	Dec. 31, 2011 5.20% Series due 2040 EDE	Apr. 30, 2012 7.0% Series due 2024	Dec. 31, 2012 7.0% Series due 2024 EDE	Dec. 31, 2011 7.0% Series due 2024 EDE	Dec. 31, 2012 7.0% Series due 2024 EDE On or after April 1, 2012	Dec. 31, 2012 6.82% Series due 2036 EDG	Dec. 31, 2011 6.82% Series due 2036 EDG	Oct. 30, 2012 3.73% First Mortgage Bonds due 2033	Dec. 31, 2012 3.73% First Mortgage Bonds due 2033	Oct. 30, 2012 4.32% First Mortgage Bonds due 2043	Dec. 31, 2012 4.32% First Mortgage Bonds due 2043	Oct. 30, 2012 4.50% Series due June 15, 2013	Jun. 30, 2012 3.58% Series Due 2027	Apr. 30, 2012 3.58% Series Due 2027	Dec. 31, 2012 3.58% Series Due 2027 EDE	Aug. 31, 2010 Senior Notes, 7.05% Series due 2022	Dec. 31, 2012 Senior Notes, 7.05% Series due 2022	Aug. 27, 2010 Senior Notes, 7.05% Series due 2022	Dec. 31, 2012 Senior Notes, 4.50% Series due 2013	Dec. 31, 2011 Senior Notes, 4.50% Series due 2013	Dec. 31, 2012 Senior Notes, 6.70% Series due 2033	Dec. 31, 2011 Senior Notes, 6.70% Series due 2033	Dec. 31, 2012 Senior Notes, 5.80% Series due 2035	Dec. 31, 2011 Senior Notes, 5.80% Series due 2035	Dec. 31, 2012 Other..	Dec. 31, 2011 Other..	Jun. 30, 2010 8.5% trust preferred securities	Jun. 28, 2010 First mortgage bonds 6.5% Series due 2010	Dec. 31, 2012 New first mortgage bonds EDE
LONG-TERM DEBT
Interest rate, stated percentage							5.50%	7.20%	7.20%		5.30%	5.30%		5.20%	5.20%	5.875%	5.875%	6.375%	6.375%		4.65%	4.65%		5.20%	5.20%		7.00%	7.00%		6.82%	6.82%		3.73%		4.32%				3.58%			7.05%	4.50%	4.50%	6.70%	6.70%	5.80%	5.80%			8.50%	6.50%
Less unamortized net discount	$ (815,000)	$ (924,000)
Total long-term debt, current and non current	692,340,000	693,192,000
Total long-term debt, current and non current	693,154,000			488,000,000	488,029,000			25,000,000	25,000,000			8,000,000			5,200,000	80,000,000	80,000,000	90,000,000	90,000,000		100,000,000	100,000,000		50,000,000	50,000,000			74,829,000		55,000,000	55,000,000								88,000,000				98,000,000	98,000,000	62,000,000	62,000,000	40,000,000	40,000,000	5,155,000	6,087,000
Current obligations of long term debt	(415,000)	(641,000)
Current obligations under capital lease	(299,000)	(292,000)
Percentage of principal amount at which the entity may redeem all the notes											100.00%			100.00%		100.00%		100.00%			100.00%			100.00%					100.00%	100.00%									100.00%		100.00%		100.00%		100.00%		100.00%
Total long-term debt	691,626,000	692,259,000
Debt to be redeemed																																				98,000,000
Debt redeemed										8,000,000			5,200,000													74,800,000
Aggregate principal amount of debt entered into in private placement																																30,000,000		120,000,000				88,000,000
Principal amount of first mortgage bonds issued																				100,000,000			50,000,000														50,000,000	38,000,000
Net proceeds (after payment of expenses)																				98,800,000			49,100,000
Aggregate principal amount redeemed																																								48,300,000											50,000,000
Number of trust preferred securities redeemed (in shares)																																																			2
Shelf registration statement, amount			400,000,000
Number of states in the entity's electric service territory	4
Maximum amount of securities to be issued in the form of first mortgage bonds						250,000,000
Amount that would remain available after giving effect to issuance of new first mortgage bonds																																																					12,000,000
Maximum amount of securities to be issued in the form of new first mortgage bonds																																																					150,000,000
Effective period to use proceeds under shelf to fund capital expenditures, refinancings of existing debt or general corporate needs						3 years
Number of consecutive months within the fifteen months preceding issuance to determine net earnings to annual interest requirement ratio						12 months
Number of months preceding issuance to determine net earnings to annual interest requirement ratio						15 months
Maximum principal amount outstanding at any one time						1,000,000,000	300,000,000
Net earnings to annual interest requirement ratio						2
Debt permitted to be issued on compliance of interest coverage ratio covenant						609,200,000	12,800,000
Interest rate assumed on debt permitted to be issued on compliance of interest coverage ratio covenant (as a percent)						5.50%
New bonds to be issued as a percentage of net property additions						60.00%	75.00%
Debt permitted to be issued on compliance of amount of retired bonds and percentage of net property additions covenant						$ 776,700,000
Number of most recent fiscal quarters used in calculating the interest coverage ratio as per the terms of debt instrument covenants							12 months
Ratio of EBITDA to interest charges, minimum							2.0