CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Revenues	$ 7,301,204	$ 6,273,787	$ 4,465,657
Operating Expenses:
Purchased Power and Transmission	2,482,954	2,084,364	1,657,914
Operations and Maintenance	1,514,986	1,583,070	1,095,358
Depreciation	610,777	519,010	302,192
Amortization of Regulatory Assets/(Liabilities), Net	206,322	79,762	91,080
Amortization of Rate Reduction Bonds	42,581	142,019	69,912
Energy Efficiency Programs	401,919	313,149	131,415
Taxes Other Than Income Taxes	512,230	434,207	323,610
Total Operating Expenses	5,771,769	5,155,581	3,671,481
Operating Income	1,529,435	1,118,206	794,176
Interest Expense:
Interest on Long-Term Debt	340,970	316,987	231,630
Interest on Rate Reduction Bonds	422	6,168	8,611
Other Interest	(2,693)	6,790	10,184
Total Interest Expense	338,699	329,945	250,425
Other Income/(Loss), Net	29,894	19,742	27,715
Income Before Income Tax Expense	1,220,630	808,003	571,466
Income Tax Expense	426,941	274,926	170,953
Net Income	793,689	533,077	400,513
Net Income Attributable to Noncontrolling Interests	7,682	7,132	5,820
Net Income Attributable to Controlling Interests	786,007	525,945	394,693
Diluted Earnings Per Common Share	$ 2.49	$ 1.89	$ 2.22
Basic Earnings Per Common Share	$ 2.49	$ 1.90	$ 2.22
Weighted Average Common Shares Outstanding:
Basic	315,311,387	277,209,819	177,410,167
Diluted	316,211,160	277,993,631	177,804,568
The Connecticut Light And Power Company [Member]
Operating Revenues	2,442,341	2,407,449	2,548,387
Operating Expenses:
Purchased Power and Transmission	872,769	858,231	982,514
Operations and Maintenance	523,247	635,733	580,736
Depreciation	177,603	166,853	157,747
Amortization of Regulatory Assets/(Liabilities), Net	4,870	14,372	61,025
Energy Efficiency Programs	89,858	89,299	90,297
Taxes Other Than Income Taxes	234,418	215,972	212,885
Total Operating Expenses	1,902,765	1,980,460	2,085,204
Operating Income	539,576	426,989	463,183
Interest Expense:
Interest on Long-Term Debt	130,620	124,894	131,918
Other Interest	3,030	8,233	809
Total Interest Expense	133,650	133,127	132,727
Other Income/(Loss), Net	15,149	10,300	9,741
Income Before Income Tax Expense	421,075	304,162	340,197
Income Tax Expense	141,663	94,437	90,033
Net Income	279,412	209,725	250,164
NSTAR Electric Company [Member]
Operating Revenues	2,493,479	2,300,997	2,403,053
Operating Expenses:
Purchased Power and Transmission	849,149	788,252	905,226
Operations and Maintenance	376,360	431,802	387,533
Depreciation	180,298	171,070	163,368
Amortization of Regulatory Assets/(Liabilities), Net	230,148	117,682	82,979
Amortization of Rate Reduction Bonds	15,054	90,322	90,322
Energy Efficiency Programs	206,536	201,234	175,747
Taxes Other Than Income Taxes	127,778	119,219	111,705
Total Operating Expenses	1,985,323	1,919,581	1,916,880
Operating Income	508,156	381,416	486,173
Interest Expense:
Interest on Long-Term Debt	79,088	87,100	90,040
Interest on Rate Reduction Bonds	399	3,585	7,226
Other Interest	(9,104)	(20,631)	(27,839)
Total Interest Expense	70,383	70,054	69,427
Other Income/(Loss), Net	3,639	2,846	1,434
Income Before Income Tax Expense	441,412	314,208	418,180
Income Tax Expense	172,866	123,966	165,686
Net Income	268,546	190,242	252,494
Public Service Company Of New Hampshire [Member]
Operating Revenues	935,402	988,013	1,013,003
Operating Expenses:
Purchased Power and Transmission	269,754	319,253	327,905
Operations and Maintenance	267,797	263,234	278,153
Depreciation	91,581	87,602	76,167
Amortization of Regulatory Assets/(Liabilities), Net	(20,387)	(24,086)	25,383
Amortization of Rate Reduction Bonds	19,748	56,645	53,389
Energy Efficiency Programs	14,494	14,245	12,917
Taxes Other Than Income Taxes	67,196	66,025	58,985
Total Operating Expenses	710,183	782,918	832,899
Operating Income	225,219	205,095	180,104
Interest Expense:
Interest on Long-Term Debt	44,370	46,228	36,832
Interest on Rate Reduction Bonds	(154)	2,687	6,276
Other Interest	1,960	1,313	1,039
Total Interest Expense	46,176	50,228	44,147
Other Income/(Loss), Net	3,455	3,008	14,255
Income Before Income Tax Expense	182,498	157,875	150,212
Income Tax Expense	71,101	60,993	49,945
Net Income	111,397	96,882	100,267
Western Massachusetts Electric Company [Member]
Operating Revenues	472,724	441,164	417,315
Operating Expenses:
Purchased Power and Transmission	147,059	136,086	161,480
Operations and Maintenance	96,194	97,031	80,241
Depreciation	37,568	29,971	26,455
Amortization of Regulatory Assets/(Liabilities), Net	(3,206)	410	4,492
Amortization of Rate Reduction Bonds	7,780	17,632	16,523
Energy Efficiency Programs	39,524	27,802	21,804
Taxes Other Than Income Taxes	28,458	21,458	17,957
Total Operating Expenses	353,377	330,390	328,952
Operating Income	119,347	110,774	88,363
Interest Expense:
Interest on Long-Term Debt	23,625	23,462	20,023
Interest on Rate Reduction Bonds	177	1,229	2,335
Other Interest	1,049	1,943	1,254
Total Interest Expense	24,851	26,634	23,612
Other Income/(Loss), Net	3,310	2,503	1,489
Income Before Income Tax Expense	97,806	86,643	66,240
Income Tax Expense	37,368	32,140	23,186
Net Income	$ 60,438	$ 54,503	$ 43,054