CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income	$ 236,493	$ 211,380	$ 603,576	$ 614,413
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	509	509	1,528	1,539
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(216)	(38)	242	(810)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	1,042	1,611	4,089	4,738
Other Comprehensive Income (Loss), Net of Tax, Total	1,335	2,082	5,859	5,467
Comprehensive Income Attributable to Noncontrolling Interests	(1,879)	(1,879)	(5,639)	(5,803)
Comprehensive Income	235,949	211,583	603,796	614,077
The Connecticut Light And Power Company [Member]
Net Income	83,876	66,323	200,560	219,188
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111	111	333	333
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(7)	(1)	8	(27)
Other Comprehensive Income (Loss), Net of Tax, Total	104	110	341	306
Comprehensive Income	83,980	66,433	200,901	219,494
NSTAR Electric Company [Member]
Net Income	115,574	107,009	233,791	213,162
Public Service Company Of New Hampshire [Member]
Net Income	28,236	28,353	84,955	84,543
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	290	290	871	872
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(13)	(2)	14	(47)
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	277	288	885	822
Comprehensive Income	28,513	28,641	85,840	85,365
Western Massachusetts Electric Company [Member]
Net Income	14,665	15,025	39,785	50,041
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	85	85	254	254
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(2)	0	2	(8)
Other Comprehensive Income (Loss), Net of Tax, Total	83	85	256	246
Comprehensive Income	$ 14,748	$ 15,110	$ 40,041	$ 50,287