CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Operating Revenues	$ 1,861,529	$ 1,114,892	$ 4,589,835	$ 3,397,624
Operating Expenses:
Purchased Power and Transmission	602,751	406,237	1,540,110	1,285,483
Operations And Maintenance	395,531	255,551	1,187,471	788,875
Depreciation	144,475	75,196	369,798	222,784
Amortization of Regulatory Assets/(Liabilities), Net	43,835	36,163	74,851	86,653
Amortization of Rate Reduction Bonds	43,044	17,680	102,144	52,047
Energyefficiencyandrenewableenergyprograms	98,326	35,255	209,089	99,658
Taxes Other Than Income Taxes	120,662	84,994	319,559	252,817
Total Operating Expenses	1,448,624	911,076	3,803,022	2,788,317
Operating Income	412,905	203,816	786,813	609,307
Interest Expense:
Interest on Long-Term Debt	86,459	57,461	233,352	171,905
Interest on Rate Reduction Bonds	1,681	2,018	5,168	6,889
Other Interest	2,221	4,453	7,336	5,922
Total Interest Expense	90,361	63,932	245,856	184,716
Other Income/(Loss), Net	4,324	1,430	14,904	19,077
Income Before Income Tax Expense	326,868	141,314	555,861	443,668
Income Tax Expense	117,360	49,883	199,379	157,934
Net Income	209,508	91,431	356,482	285,734
Net Income Attributable to Noncontrolling Interests	1,880	1,470	5,253	4,340
Net Income Attributable to Controlling Interests	207,628	89,961	351,229	281,394
Diluted Earnings Per Common Share	$ 0.66	$ 0.51	$ 1.32	$ 1.58
Basic Earnings Per Common Share	$ 0.66	$ 0.51	$ 1.33	$ 1.59
Common Stock Dividends Per Share Declared	$ 0.34	$ 0.28	$ 0.97	$ 0.83
Weighted Average Common Shares Outstanding:
Basic	314,806,441	177,497,862	264,636,636	177,344,481
Diluted	315,805,796	177,835,348	265,353,377	177,647,694
The Connecticut Light And Power Company [Member]
Operating Revenues	658,111	673,666	1,812,218	1,955,361
Operating Expenses:
Purchased Power and Transmission	241,046	266,350	658,743	768,687
Operations And Maintenance	141,913	130,714	480,286	403,125
Depreciation	41,863	39,711	124,451	117,629
Amortization of Regulatory Assets/(Liabilities), Net	8,656	15,688	19,912	48,027
Energyefficiencyandrenewableenergyprograms	25,237	24,914	68,205	69,629
Taxes Other Than Income Taxes	59,687	58,552	168,667	169,745
Total Operating Expenses	518,402	535,929	1,520,264	1,576,842
Operating Income	139,709	137,737	291,954	378,519
Interest Expense:
Interest on Long-Term Debt	31,429	33,326	94,646	100,085
Other Interest	2,162	1,893	6,223	(815)
Total Interest Expense	33,591	35,219	100,869	99,270
Other Income/(Loss), Net	2,889	(2,356)	8,636	4,308
Income Before Income Tax Expense	109,007	100,162	199,721	283,557
Income Tax Expense	34,121	33,634	63,917	100,057
Net Income	74,886	66,528	135,804	183,500
Public Service Company Of New Hampshire [Member]
Operating Revenues	256,949	259,648	755,051	769,309
Operating Expenses:
Purchased Power and Transmission	76,008	77,698	239,173	247,072
Operations And Maintenance	67,547	65,336	200,960	205,806
Depreciation	22,264	18,403	65,282	54,432
Amortization of Regulatory Assets/(Liabilities), Net	(6,356)	17,271	(6,179)	35,303
Amortization of Rate Reduction Bonds	16,112	13,609	43,855	39,748
Energyefficiencyandrenewableenergyprograms	4,030	3,730	10,824	9,571
Taxes Other Than Income Taxes	16,046	15,133	47,406	44,034
Total Operating Expenses	195,651	211,180	601,321	635,966
Operating Income	61,298	48,468	153,730	133,343
Interest Expense:
Interest on Long-Term Debt	11,434	8,484	34,537	25,425
Interest on Rate Reduction Bonds	564	1,468	2,366	5,038
Other Interest	609	416	1,301	761
Total Interest Expense	12,607	10,368	38,204	31,224
Other Income/(Loss), Net	(353)	3,293	2,237	12,112
Income Before Income Tax Expense	48,338	41,393	117,763	114,231
Income Tax Expense	21,106	15,759	48,037	39,468
Net Income	27,232	25,634	69,726	74,763
Western Massachusetts Electric Company [Member]
Operating Revenues	112,470	104,515	333,331	309,589
Operating Expenses:
Purchased Power and Transmission	32,028	41,246	105,297	124,440
Operations And Maintenance	24,765	19,161	75,214	60,467
Depreciation	7,464	6,681	22,154	19,644
Amortization of Regulatory Assets/(Liabilities), Net	1,021	2,810	634	3,538
Amortization of Rate Reduction Bonds	4,352	4,071	13,127	12,299
Energyefficiencyandrenewableenergyprograms	9,190	6,110	19,679	16,491
Taxes Other Than Income Taxes	5,505	4,650	15,365	13,395
Total Operating Expenses	84,325	84,729	251,470	250,274
Operating Income	28,145	19,786	81,861	59,315
Interest Expense:
Interest on Long-Term Debt	5,783	4,913	17,454	14,389
Interest on Rate Reduction Bonds	272	550	1,029	1,852
Other Interest	714	529	1,550	785
Total Interest Expense	6,769	5,992	20,033	17,026
Other Income/(Loss), Net	685	(722)	1,965	259
Income Before Income Tax Expense	22,061	13,072	63,793	42,548
Income Tax Expense	7,977	4,638	24,385	15,977
Net Income	14,084	8,434	39,408	26,571
NSTAR Electric Company [Member]
Operating Revenues	693,653	724,686	1,784,755	1,854,507
Operating Expenses:
Purchased Power and Transmission	222,753	262,118	622,265	717,180
Operations And Maintenance	83,329	100,991	340,547	286,044
Depreciation	42,494	40,399	127,692	123,556
Amortization of Regulatory Assets/(Liabilities), Net	41,888	27,065	87,912	56,734
Amortization of Rate Reduction Bonds	22,581	22,581	67,742	67,742
Energyefficiencyandrenewableenergyprograms	55,969	59,204	138,360	132,160
Taxes Other Than Income Taxes	30,520	28,580	89,689	84,069
Total Operating Expenses	499,534	540,938	1,474,207	1,467,485
Operating Income	194,119	183,748	310,548	387,022
Interest Expense:
Interest on Long-Term Debt	22,386	22,548	66,953	67,724
Interest on Rate Reduction Bonds	853	1,742	3,106	5,795
Other Interest	(4,704)	(6,350)	(16,137)	(21,679)
Total Interest Expense	18,535	17,940	53,922	51,840
Other Income/(Loss), Net	551	(419)	1,778	1,300
Income Before Income Tax Expense	176,135	165,389	258,404	336,482
Income Tax Expense	69,373	65,569	102,220	133,115
Net Income	$ 106,762	$ 99,820	$ 156,184	$ 203,367