Financing (Details) (USD $)	9 Months Ended		0 Months Ended		0 Months Ended			1 Months Ended		1 Months Ended		1 Months Ended			1 Months Ended
	Sep. 30, 2012 First mortgage bonds EDE	Sep. 30, 2012 3.73% First Mortgage Bonds due 2033	Oct. 30, 2012 3.73% First Mortgage Bonds due 2033 Issuance of debt	Sep. 30, 2012 4.32% First Mortgage Bonds due 2043	Oct. 30, 2012 4.32% First Mortgage Bonds due 2043 Issuance of debt	Oct. 30, 2012 4.50% Series due June 15, 2013	Sep. 30, 2012 4.50% Series due June 15, 2013	Apr. 30, 2012 7.0% Series due 2024	Sep. 30, 2012 7.0% Series due 2024	Apr. 30, 2012 5.3% Pollution Control Series due 2013	Sep. 30, 2012 5.3% Pollution Control Series due 2013	Apr. 30, 2012 5.2% Pollution Control Series due 2013	Sep. 30, 2012 5.2% Pollution Control Series due 2013	Sep. 30, 2012 3.58% Series Due 2027	Jun. 30, 2012 3.58% Series Due 2027 Issuance of debt	Apr. 30, 2012 3.58% Series Due 2027 Issuance of debt
Financing
Interest rate, stated percentage		3.73%		4.32%			4.50%		7.00%		5.30%		5.20%	3.58%
Debt to be redeemed						$ 98,000,000
Debt redeemed								74,800,000		8,000,000		5,200,000
Aggregate principal amount of debt entered into in private placement			30,000,000		120,000,000											88,000,000
Settlement of bond issuance under private placement															50,000,000	38,000,000
Maximum principal amount outstanding at any one time	$ 1,000,000,000