LONG-TERM DEBT (Details) (USD $)	0 Months Ended	12 Months Ended	0 Months Ended
	Dec. 13, 2013	Dec. 31, 2014	Oct. 30, 2012	Oct. 15, 2014	Dec. 31, 2013
LONG-TERM DEBT
Less unamortized net discount		$ (686,000)			$ (739,000)
Total long-term debt, current and non current		803,481,000			743,702,000
Total long-term debt, current and non current		804,167,000
Current obligations under capital lease		(292,000)			(274,000)
Total long-term debt		803,189,000			743,428,000
Shelf registration statement, amount	200,000,000	200,000,000
Effective period to use proceeds under shelf to fund capital expenditures, refinancings of existing debt or general corporate needs	3 years	3 years
EDE
LONG-TERM DEBT
Debt permitted to be issued on compliance of interest coverage ratio covenant		615,900,000
First mortgage bonds
LONG-TERM DEBT
Total long-term debt, current and non current		698,000,000			638,000,000
First mortgage bonds | EDE
LONG-TERM DEBT
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
Net earnings to annual interest requirement ratio		2
Maximum principal amount outstanding at any one time		1,000,000,000
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%
First mortgage bonds | EDE | Low end of range
LONG-TERM DEBT
Debt permitted to be issued on compliance of amount of retired bonds and percentage of net property additions covenant		952,500,000
First mortgage bonds | EDG
LONG-TERM DEBT
Maximum principal amount outstanding at any one time		300,000,000
Interest rate assumed on debt permitted to be issued on compliance of interest coverage ratio covenant (as a percent)		5.50%
Debt permitted to be issued on compliance of amount of retired bonds and percentage of net property additions covenant		19,700,000
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
First mortgage bonds | EDG | High end of range
LONG-TERM DEBT
New bonds to be issued as a percentage of net property additions		75.00%
7.20% Series due 2016 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		25,000,000			25,000,000
Interest rate, stated percentage		7.20%			7.20%
5.875% Series due 2037 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		80,000,000			80,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		5.875%
6.375% Series due 2018 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		90,000,000			90,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		6.375%			6.375%
4.65% Series due 2020 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		100,000,000			100,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		4.65%			4.65%
5.20% Series due 2040 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		50,000,000			50,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		5.20%
3.58% Series Due 2027 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		88,000,000			88,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		3.58%			3.58%
3.73% Series due 2033
LONG-TERM DEBT
Aggregate principal amount of debt entered into in private placement			30,000,000
Interest rate, stated percentage		3.73%
3.73% Series due 2033 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		30,000,000			30,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		3.73%
4.32% Series due 2043
LONG-TERM DEBT
Aggregate principal amount of debt entered into in private placement			120,000,000
Interest rate, stated percentage		4.32%
4.32% Series due 2043 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		120,000,000			120,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		4.32%
4.27% Series due 2044
LONG-TERM DEBT
Aggregate principal amount of debt entered into in private placement				60,000,000
Interest rate, stated percentage		4.27%
4.27% Series due 2044 | EDE
LONG-TERM DEBT
Total long-term debt, current and non current		60,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		4.27%
6.82% Series due 2036 | EDG
LONG-TERM DEBT
Total long-term debt, current and non current		55,000,000			55,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		6.82%			6.82%
Senior Notes, 4.50% Series due 2013
LONG-TERM DEBT
Debt to be redeemed		98,000,000
Interest rate, stated percentage		4.50%
Senior Notes, 6.70% Series due 2033
LONG-TERM DEBT
Total long-term debt, current and non current		62,000,000			62,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		6.70%			6.70%
Senior Notes, 5.80% Series due 2035
LONG-TERM DEBT
Total long-term debt, current and non current		40,000,000			40,000,000
Percentage of principal amount at which the entity may redeem all the notes		100.00%
Interest rate, stated percentage		5.80%			5.80%
Other.
LONG-TERM DEBT
Total long-term debt, current and non current		4,167,000			4,441,000
New first mortgage bonds | EDE | High end of range
LONG-TERM DEBT
Debt permitted to be issued based on the limit on the principal amount and current level of outstanding bonds		$ 357,000,000