ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
AOCI Cash Flow Hedging Component [Abstract]
Beginning Balance -AOCI From CF Hedges Effect Net Of Tax	$ (14,400,000)	$ (16,400,000)
OCI Amortization of Cash Flow Hedge, Net of Tax	500,000	500,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	509,000	516,000
Ending Balance - AOCI From CFHedges Effect Net Of Tax	(13,900,000)	(15,900,000)
AOCI Unrealized GainLoss component [Abstract]
AOCI Unrealized Gains/Losses on Other Securities	400,000	1,300,000
OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax	200,000	(100,000)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	240,000	(181,000)
AOCI Unrealized Gains/Losses on Other Securities-Ending Balance	600,000	1,200,000
AOCI Defined Benefit Component [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(32,000,000)	57,800,000
Reclassification of DB Plans	1,000,000	1,600,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	961,000	1,621,000
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(31,000,000)	(56,200,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(46,031,000)	(72,900,000)
AmountReclassifiedFromAOCI	1,500,000	2,100,000
OtherComprehensiveIncomeBeforeReclassifications	200,000	(100,000)
Other Comprehensive Income (Loss), Net of Tax, Total	1,710,000	1,956,000
AOCI ending Balance	(44,321,000)	(70,900,000)
Reclassication of Items out of AOCI [Abstract]
OCI Reclass CF Hedging Tax	300,000	300,000
OCI Amortization of Cash Flow Hedges, Before Tax	(800,000)	(800,000)
OCI Amortization of Cash Flow Hedge, Net of Tax	(500,000)	(500,000)
Amortization of actuarial gain or loss	(1,700,000)	(2,600,000)
OCI Defined Benefit Plan Tax	700,000	1,000,000
Reclassification of DB Plans	(1,000,000)	(1,600,000)
AmountReclassifiedFromAOCI	(1,500,000)	(2,100,000)
The Connecticut Light And Power Company [Member]
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111,000	111,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	8,000	(6,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(1,387,000)
Other Comprehensive Income (Loss), Net of Tax, Total	119,000	105,000
AOCI ending Balance	(1,268,000)
Public Service Company Of New Hampshire [Member]
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	290,000	291,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	14,000	(11,000)
AOCI Defined Benefit Component [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	0	(3,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(8,550,000)
Other Comprehensive Income (Loss), Net of Tax, Total	304,000	277,000
AOCI ending Balance	(8,246,000)
Western Massachusetts Electric Company [Member]
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	85,000	85,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	2,000	(2,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance	(3,517,000)
Other Comprehensive Income (Loss), Net of Tax, Total	87,000	83,000
AOCI ending Balance	$ (3,430,000)