CAPITALIZATION (Details) (USD $)	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Schedule of Capitalization, Long-term Debt [Line Items]
Issuances of long term debt	$ (51,050,000)	$ (109,000,000)
Ownership percentage in joint venture (in hundredths)	50.00%
Common Stock [Member]
Temporary Equity [Line Items]
Common stock outstanding (in shares)	50,542,709
Common stock par value (in dollars per share)	$ 0.00
Series B Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate (in hundredths)	7.38%
Balance of debt repaid	45,000,000
Series A Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate (in hundredths)	7.23%
Balance of debt repaid	4,300,000
Credit Facility (EBL) [Member] | United Illuminating Company (UI) [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Balance of debt repaid	63,000,000
Ownership percentage in joint venture (in hundredths)	50.00%
Secured Medium Term Notes due 2021 [Member] | The Southern Connecticut Gas Company (SCG) [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate (in hundredths)	3.88%
Issuances of long term debt	25,000,000
Secured Medium Term Notes due 2041 [Member] | The Southern Connecticut Gas Company (SCG) [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate (in hundredths)	5.39%
Issuances of long term debt	25,000,000
Senior Secured Medium Term Notes [Member] | The Southern Connecticut Gas Company (SCG) [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate (in hundredths)	6.59%
Balance of debt repaid	30,000,000
Berkshire [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate (in hundredths)	4.76%
Balance of debt repaid	$ 3,000,000
United Illuminating Company (UI) [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Ownership percentage in joint venture (in hundredths)	50.00%