SUPPLEMENTARY INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Depreciation and Amortization
Property, plant and equipment depreciation	$ 27,908	$ 23,793	$ 54,495	$ 47,438
Amortization of nuclear plant regulatory assets	10,405	10,176	21,161	20,924
Amortization of other regulatory assets	4,722	5,097	13,926	15,663
Other amortization	13	11	25	23
Total Amortization	15,140	15,284	35,112	36,610
Total depreciation and amortization	43,048	39,077	89,607	84,048
Taxes - Other than Income Taxes - Operating:
Connecticut gross earnings	12,421	15,531	31,852	39,797
Local real estate and personal property	9,575	8,047	18,764	16,470
Payroll taxes	1,732	2,324	3,630	5,362
Other	94	(2)	176	(222)
Total Taxes - Other than Income Taxes	23,822	25,900	54,422	61,407
Other Income and (Deductions), net
Interest income	653	1,072	1,075	1,794
Allowance for funds used during construction - equity	1,636	2,672	3,884	5,317
Allowance for funds used during construction - debt	1,634	2,261	3,804	4,276
Conservation & Load Management incentive	251	271	502	542
ISO load response, net	(132)	(251)	1,258	(92)
Miscellaneous other income and (deductions) - net	830	(421)	3,266	(1,568)
Total Other Income and (Deductions), net	$ 4,872	$ 5,604	$ 13,789	$ 10,269