Financing (Details) (USD $)	9 Months Ended	0 Months Ended			0 Months Ended		0 Months Ended
	Sep. 30, 2013 First mortgage bonds EDE	Jun. 15, 2013 4.50% Series due 2013	Sep. 30, 2013 4.50% Series due 2013	Sep. 30, 2013 3.73% First Mortgage Bonds due May 30, 2033	Oct. 30, 2012 3.73% First Mortgage Bonds due May 30, 2033 Issuance of debt	Sep. 30, 2013 4.32% First Mortgage Bonds due May 30, 2043	Oct. 30, 2012 4.32% First Mortgage Bonds due May 30, 2043 Issuance of debt
Financing
Interest rate, stated percentage			4.50%	3.73%		4.32%
Aggregate principal amount of debt entered into in private placement					$ 30,000,000		$ 120,000,000
Maximum principal amount outstanding at any one time	1,000,000,000
Principal amount of debt redeemed		$ 98,000,000