CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income	$ 793,689	$ 533,077	$ 400,513
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	2,049	1,971	(14,177)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(940)	217	506
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	25,714	(4,356)	(13,645)
Other Comprehensive Income (Loss), Net of Tax, Total	26,823	(2,168)	(27,316)
Comprehensive Income Attributable to Noncontrolling Interests	(7,682)	(7,132)	(5,820)
Comprehensive Income	812,830	523,777	367,377
The Connecticut Light And Power Company [Member]
Net Income	279,412	209,725	250,164
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	444	444	445
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(31)	7	17
Other Comprehensive Income (Loss), Net of Tax, Total	413	451	462
Comprehensive Income	279,825	210,176	250,626
NSTAR Electric Company [Member]
Net Income	268,546	190,242	252,494
Public Service Company Of New Hampshire [Member]
Net Income	111,397	96,882	100,267
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	1,162	1,162	(10,260)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(54)	13	29
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(3)	2	0
Other Comprehensive Income (Loss), Net of Tax, Total	1,105	1,177	(10,231)
Comprehensive Income	112,502	98,059	90,036
Western Massachusetts Electric Company [Member]
Net Income	60,438	54,503	43,054
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	338	338	(4,108)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(9)	2	5
Other Comprehensive Income (Loss), Net of Tax, Total	329	340	(4,103)
Comprehensive Income	$ 60,767	$ 54,843	$ 38,951