CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net Income	$ 237,836	$ 229,968
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	509	516
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	240	(181)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	961	1,621
Other Comprehensive Income (Loss), Net of Tax, Total	1,710	1,956
Comprehensive Income Attributable to Noncontrolling Interests	(1,879)	(1,879)
Comprehensive Income	237,667	230,045
The Connecticut Light And Power Company [Member]
Net Income	79,299	85,008
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111	111
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	8	(6)
Other Comprehensive Income (Loss), Net of Tax, Total	119	105
Comprehensive Income	79,418	85,113
NSTAR Electric Company [Member]
Net Income	58,087	48,122
Public Service Company Of New Hampshire [Member]
Net Income	32,638	28,996
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	290	291
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	14	(11)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	0	(3)
Other Comprehensive Income (Loss), Net of Tax, Total	304	277
Comprehensive Income	32,942	29,273
Western Massachusetts Electric Company [Member]
Net Income	18,102	18,603
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	85	85
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	2	(2)
Other Comprehensive Income (Loss), Net of Tax, Total	87	83
Comprehensive Income	$ 18,189	$ 18,686