ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent [Abstract]
Cash Flow Hedge Loss To Be Reclassified Within Twelve Months	$ 3,400,000
Pension Serp And Pbop Gain Loss To Be Reclassified Within Twelve Months	6,500,000
AOCI Cash Flow Hedging Component [Abstract]
Beginning Balance -AOCI From CF Hedges Effect Net Of Tax	(16,400,000)
OCI Amortization of Cash Flow Hedge, Net of Tax	2,000,000	2,000,000	700,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(2,049,000)	(1,971,000)	14,177,000
Ending Balance - AOCI From CFHedges Effect Net Of Tax	(14,400,000)	(16,400,000)
AOCI Unrealized GainLoss component [Abstract]
AOCI Unrealized Gains/Losses on Other Securities	1,300,000
OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax	(900,000)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(940,000)	217,000	506,000
AOCI Unrealized Gains/Losses on Other Securities-Ending Balance	400,000	1,300,000
AOCI Defined Benefit Component [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(57,800,000)
Reclassification of DB Plans	6,400,000	5,800,000	3,900,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	25,714,000	(4,356,000)	(13,645,000)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(32,000,000)	(57,800,000)
Losses arising before reclassification	19,400,000
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(72,854,000)
AmountReclassifiedFromAOCI	8,400,000	7,800,000	4,600,000
OtherComprehensiveIncomeBeforeReclassifications	18,500,000
Other Comprehensive Income (Loss), Net of Tax, Total	26,823,000	(2,168,000)	(27,316,000)
AOCI ending Balance	(46,031,000)	(72,854,000)
Reclassication of Items out of AOCI [Abstract]
OCI Reclass CF Hedging Tax	1,400,000	1,300,000	600,000
OCI Amortization of Cash Flow Hedges, Before Tax	(3,400,000)	(3,300,000)	(1,300,000)
OCI Amortization of Cash Flow Hedge, Net of Tax	(2,000,000)	(2,000,000)	(700,000)
OCI Amortization of Prior Service Cost	(200,000)	(200,000)	(300,000)
Amortization of actuarial gain or loss	(10,500,000)	(8,900,000)	(5,700,000)
Amortization of Transition Obligation		(200,000)	(200,000)
OCI Defined Benefit Plan Adjustment Before Tax	(10,700,000)	(9,300,000)	(6,200,000)
OCI Defined Benefit Plan Tax	4,300,000	3,500,000	2,300,000
Reclassification of DB Plans	(6,400,000)	(5,800,000)	(3,900,000)
AmountReclassifiedFromAOCI	(8,400,000)	(7,800,000)	(4,600,000)
OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTaxAbstract
OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	(11,400,000)	6,200,000	10,200,000
OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax			10,200,000
The Connecticut Light And Power Company [Member]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent [Abstract]
Cash Flow Hedge Loss To Be Reclassified Within Twelve Months	700,000
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(444,000)	(444,000)	(445,000)
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(31,000)	7,000	17,000
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(1,800,000)
Other Comprehensive Income (Loss), Net of Tax, Total	413,000	451,000	462,000
AOCI ending Balance	(1,387,000)	(1,800,000)
Public Service Company Of New Hampshire [Member]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent [Abstract]
Cash Flow Hedge Loss To Be Reclassified Within Twelve Months	2,000,000
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(1,162,000)	(1,162,000)	10,260,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(54,000)	13,000	29,000
AOCI Defined Benefit Component [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(3,000)	2,000	0
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(9,655,000)
Other Comprehensive Income (Loss), Net of Tax, Total	1,105,000	1,177,000	(10,231,000)
AOCI ending Balance	(8,550,000)	(9,655,000)
Western Massachusetts Electric Company [Member]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent [Abstract]
Cash Flow Hedge Loss To Be Reclassified Within Twelve Months	500,000
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(338,000)	(338,000)	4,108,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(9,000)	2,000	5,000
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(3,846,000)
Other Comprehensive Income (Loss), Net of Tax, Total	329,000	340,000	(4,103,000)
AOCI ending Balance	$ (3,517,000)	$ (3,846,000)