CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Income	$ 129,247	$ 173,064	$ 367,083	$ 403,032
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	510	514	1,019	1,030
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	218	(591)	458	(772)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	2,086	1,506	3,047	3,127
Other Comprehensive Income (Loss), Net of Tax, Total	2,814	1,429	4,524	3,385
Comprehensive Income Attributable to Noncontrolling Interests	(1,880)	(2,043)	(3,759)	(3,922)
Comprehensive Income	130,181	172,450	367,848	402,495
The Connecticut Light And Power Company [Member]
Net Income	37,385	67,857	116,684	152,865
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111	111	222	222
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	7	(20)	15	(26)
Other Comprehensive Income (Loss), Net of Tax, Total	118	91	237	196
Comprehensive Income	37,503	67,948	116,921	153,061
NSTAR Electric Company [Member]
Net Income	60,129	58,031	118,216	106,153
Public Service Company Of New Hampshire [Member]
Net Income	24,080	27,194	56,718	56,189
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	291	291	581	582
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	12	(34)	26	(45)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	0	0	0	(3)
Other Comprehensive Income (Loss), Net of Tax, Total	303	257	607	534
Comprehensive Income	24,383	27,451	57,325	56,723
Western Massachusetts Electric Company [Member]
Net Income	7,018	16,414	25,120	35,016
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	84	84	169	169
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	2	(6)	4	(8)
Other Comprehensive Income (Loss), Net of Tax, Total	86	78	173	161
Comprehensive Income	$ 7,104	$ 16,492	$ 25,293	$ 35,177