ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 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	1,000,000	1,000,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	510,000	514,000	1,019,000	1,030,000
Ending Balance - AOCI From CFHedges Effect Net Of Tax	(13,400,000)	(15,400,000)	(13,400,000)	(15,400,000)
AOCI Unrealized GainLoss component [Abstract]
AOCI Unrealized Gains/Losses on Other Securities			400,000	1,300,000
OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax			500,000	(700,000)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	218,000	(591,000)	458,000	(772,000)
AOCI Unrealized Gains/Losses on Other Securities-Ending Balance	900,000	600,000	900,000	600,000
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	700,000	1,500,000	1,800,000	3,100,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	2,086,000	1,506,000	3,047,000	3,127,000
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(29,000,000)	(54,700,000)	(29,000,000)	(54,700,000)
Losses arising before reclassification	1,200,000		1,200,000
AOCI Rollforward [Abstract]
AOCI Beginning Balance			(46,031,000)	(72,900,000)
AmountReclassifiedFromAOCI	1,200,000	2,000,000	2,800,000	4,100,000
OtherComprehensiveIncomeBeforeReclassifications			1,700,000	(700,000)
Other Comprehensive Income (Loss), Net of Tax, Total	2,814,000	1,429,000	4,524,000	3,385,000
AOCI ending Balance	(41,507,000)	(69,500,000)	(41,507,000)	(69,500,000)
Reclassication of Items out of AOCI [Abstract]
OCI Reclass CF Hedging Tax	300,000	300,000	700,000	700,000
OCI Amortization of Cash Flow Hedges, Before Tax	(800,000)	(800,000)	(1,700,000)	(1,700,000)
OCI Amortization of Cash Flow Hedge, Net of Tax	(500,000)	(500,000)	(1,000,000)	(1,000,000)
OCI Amortization of Prior Service Cost			(100,000)	(100,000)
Amortization of actuarial gain or loss	(1,200,000)	(2,200,000)	(2,900,000)	(4,700,000)
OCI Defined Benefit Plan Adjustment Before Tax	(1,200,000)	(2,200,000)	(3,000,000)	(4,800,000)
OCI Defined Benefit Plan Tax	500,000	700,000	1,200,000	1,700,000
Reclassification of DB Plans	(700,000)	(1,500,000)	(1,800,000)	(3,100,000)
AmountReclassifiedFromAOCI	(1,200,000)	(2,000,000)	(2,800,000)	(4,100,000)
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	222,000	222,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	7,000	(20,000)	15,000	(26,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance			(1,387,000)
Other Comprehensive Income (Loss), Net of Tax, Total	118,000	91,000	237,000	196,000
AOCI ending Balance	(1,150,000)		(1,150,000)
Public Service Company Of New Hampshire [Member]
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	291,000	291,000	581,000	582,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	12,000	(34,000)	26,000	(45,000)
AOCI Defined Benefit Component [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	0	0	0	(3,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance			(8,550,000)
Other Comprehensive Income (Loss), Net of Tax, Total	303,000	257,000	607,000	534,000
AOCI ending Balance	(7,943,000)		(7,943,000)
Western Massachusetts Electric Company [Member]
AOCI Cash Flow Hedging Component [Abstract]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	84,000	84,000	169,000	169,000
AOCI Unrealized GainLoss component [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	2,000	(6,000)	4,000	(8,000)
AOCI Rollforward [Abstract]
AOCI Beginning Balance			(3,517,000)
Other Comprehensive Income (Loss), Net of Tax, Total	86,000	78,000	173,000	161,000
AOCI ending Balance	$ (3,344,000)		$ (3,344,000)