CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Operating Revenues	1,628,684	1,047,481	2,728,307	2,282,732
Operating Expenses:
Fuel, Purchased and Net Interchange Power	542,014	382,542	937,358	879,246
Operations And Maintenance	529,977	269,701	791,940	533,323
Depreciation	144,485	73,637	225,324	147,588
Amortization of Regulatory Assets/(Liabilities), Net	25,590	16,992	31,016	50,491
Amortization of Rate Reduction Bonds	40,752	17,086	59,100	34,367
Energyefficiencyandrenewableenergyprograms	73,489	29,970	110,762	64,403
Taxes Other Than Income Taxes	112,862	79,419	198,899	167,823
Total Operating Expenses	1,469,169	869,347	2,354,399	1,877,241
Operating Income	159,515	178,134	373,908	405,491
Interest Expense:
Interest on Long-Term Debt	86,925	57,044	146,892	114,444
Interest on Rate Reduction Bonds	2,056	2,293	3,487	4,871
Other Interest	66	2,897	5,116	1,468
Total Interest Expense	89,047	62,234	155,495	120,783
Other Income/(Loss), Net	1,806	7,334	10,580	17,647
Income Before Income Tax Expense	72,274	123,234	228,993	302,355
Income Tax Expense	26,055	44,515	82,019	108,052
Net Income	46,219	78,719	146,974	194,303
Net Income Attributable to Noncontrolling Interests	1,880	1,441	3,373	2,870
Net Income Attributable to Controlling Interests	44,339	77,278	143,601	191,433
Earnings Per Share Basic And Diluted	0.15	0.44	0.60	1.08
Common Stock Dividends Per Share Declared	0.34	0.28	0.63	0.55
Weighted Average Common Shares Outstanding:
Basic	301,047,753	177,347,374	239,551,735	177,267,791
Diluted	301,816,884	177,626,992	240,127,169	177,553,995
The Connecticut Light And Power Company [Member]
Operating Revenues	562,141	608,013	1,154,106	1,281,695
Operating Expenses:
Fuel, Purchased and Net Interchange Power	196,806	230,380	417,697	502,338
Operations And Maintenance	205,471	136,669	338,373	272,411
Depreciation	41,519	38,442	82,588	77,917
Amortization of Regulatory Assets/(Liabilities), Net	3,263	13,705	11,257	32,339
Energyefficiencyandrenewableenergyprograms	20,995	21,291	42,968	44,715
Taxes Other Than Income Taxes	53,706	52,727	108,978	111,193
Total Operating Expenses	521,760	493,214	1,001,861	1,040,913
Operating Income	40,381	114,799	152,245	240,782
Interest Expense:
Interest on Long-Term Debt	31,696	33,430	63,218	66,758
Other Interest	2,075	868	4,060	(2,708)
Total Interest Expense	33,771	34,298	67,278	64,050
Other Income/(Loss), Net	447	2,058	5,747	6,663
Income Before Income Tax Expense	7,057	82,559	90,714	183,395
Income Tax Expense	124	29,924	29,796	66,423
Net Income	6,933	52,635	60,918	116,972
Public Service Company Of New Hampshire [Member]
Operating Revenues	255,105	240,191	498,102	509,661
Operating Expenses:
Fuel, Purchased and Net Interchange Power	82,116	74,372	163,165	169,375
Operations And Maintenance	68,435	76,281	133,413	140,469
Depreciation	21,811	18,122	43,018	36,030
Amortization of Regulatory Assets/(Liabilities), Net	2,798	2,465	177	18,032
Amortization of Rate Reduction Bonds	13,814	13,004	27,743	26,139
Energyefficiencyandrenewableenergyprograms	3,213	2,774	6,794	5,840
Taxes Other Than Income Taxes	15,872	15,234	31,360	28,902
Total Operating Expenses	208,059	202,252	405,670	424,787
Operating Income	47,046	37,939	92,432	84,874
Interest Expense:
Interest on Long-Term Debt	11,539	8,317	23,103	16,941
Interest on Rate Reduction Bonds	786	1,676	1,802	3,570
Other Interest	460	408	692	346
Total Interest Expense	12,785	10,401	25,597	20,857
Other Income/(Loss), Net	549	4,361	2,590	8,820
Income Before Income Tax Expense	34,810	31,899	69,425	72,837
Income Tax Expense	13,578	10,234	26,931	23,708
Net Income	21,232	21,665	42,494	49,129
Western Massachusetts Electric Company [Member]
Operating Revenues	106,836	98,390	220,861	205,074
Operating Expenses:
Fuel, Purchased and Net Interchange Power	32,715	37,965	73,269	83,195
Operations And Maintenance	27,847	20,556	50,449	41,306
Depreciation	6,994	6,625	14,691	12,963
Amortization of Regulatory Assets/(Liabilities), Net	(44)	1,526	(387)	728
Amortization of Rate Reduction Bonds	4,358	4,082	8,776	8,228
Energyefficiencyandrenewableenergyprograms	4,933	4,956	10,489	10,380
Taxes Other Than Income Taxes	4,977	4,203	9,858	8,745
Total Operating Expenses	81,780	79,913	167,145	165,545
Operating Income	25,056	18,477	53,716	39,529
Interest Expense:
Interest on Long-Term Debt	5,905	4,722	11,671	9,476
Interest on Rate Reduction Bonds	343	617	757	1,301
Other Interest	621	121	836	257
Total Interest Expense	6,869	5,460	13,264	11,034
Other Income/(Loss), Net	188	242	1,280	981
Income Before Income Tax Expense	18,375	13,259	41,732	29,476
Income Tax Expense	7,237	5,088	16,408	11,339
Net Income	11,138	8,171	25,324	18,137
NSTAR Electric Company [Member]
Operating Revenues	534,626	552,346	1,091,102	1,129,821
Operating Expenses:
Fuel, Purchased and Net Interchange Power	180,502	212,055	399,512	455,062
Operations And Maintenance	109,038	87,823	257,218	185,053
Depreciation	42,669	41,637	85,198	83,157
Amortization of Regulatory Assets/(Liabilities), Net	22,144	13,407	46,024	29,669
Amortization of Rate Reduction Bonds	22,581	22,581	45,161	45,161
Energyefficiencyandrenewableenergyprograms	35,487	32,865	82,391	72,956
Taxes Other Than Income Taxes	28,308	26,423	59,169	55,489
Total Operating Expenses	440,729	436,791	974,673	926,547
Operating Income	93,897	115,555	116,429	203,274
Interest Expense:
Interest on Long-Term Debt	22,279	22,583	44,567	45,176
Interest on Rate Reduction Bonds	927	1,839	2,253	4,053
Other Interest	(5,597)	(8,082)	(11,433)	(15,329)
Total Interest Expense	17,609	16,340	35,387	33,900
Other Income/(Loss), Net	6	910	1,227	1,719
Income Before Income Tax Expense	76,294	100,125	82,269	171,093
Income Tax Expense	30,812	39,471	32,847	67,546
Net Income	45,482	60,654	49,422	103,547