SUPPLEMENTARY INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Electric Distribution and Transmission:
Retail	$ 656,533	$ 736,576	$ 796,665
Wholesale	491	505	235
Other operating revenue	140,632	122,466	98,781
Total Electric Distribution and Transmission Revenue	797,656	859,547	895,681
Gas Distribution:
Retail	675,122	123,846
Wholesale	65,943	8,765
Other operating revenue	31,250	5,494
Total Gas Distribution Revenue	772,315	138,105
Non-utility revenues:
Other	476	14	869
Total Operating Revenues	1,570,447	997,666	896,550
Depreciation and Amortization
Property, plant and equipment depreciation	98,038	55,118	49,588
Amortization of nuclear plant regulatory assets	44,635	45,898	46,907
Amortization of other regulatory assets	24,741	12,885	1,579
Other amortization	48	45	42
Total Amortization	69,424	58,828	48,528
Depreciation and amortization	167,462	113,946	98,116
Operating:
Connecticut gross earnings	69,906	51,708	38,161
Local real estate and personal property	34,902	21,130	16,471
Payroll taxes	9,373	5,659	5,430
Other	30	205	0
Total Taxes - Other than Income Taxes	114,211	78,702	60,062
Other Income and (Deductions), net
Interest income	3,483	4,163	3,231
Allowance for funds used during construction - equity	10,539	7,180	650
Allowance for funds used during construction - debt	9,143	4,735	1,305
Conservation & Load Management incentive	1,035	1,720	765
Energy generation and load curtailment incentives	607	928	369
ISO load response, net	404	1,153	1,913
Miscellaneous other income and (deductions) - net	1,721	(2,617)	(2,647)
Total Other Income and (Deductions), net	26,932	17,262	5,586
Other Interest, net
Notes Payable	442	83	644
Other	4,774	1,470	642
Total Other Interest, net	$ 5,216	$ 1,553	$ 1,286