CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Operating Revenues	$ 1,635,862	$ 1,628,684	$ 3,630,885	$ 2,728,307
Operating Expenses:
Purchased Power and Transmission	488,302	542,014	1,236,111	937,358
Operations and Maintenance	357,169	529,977	703,261	791,940
Depreciation	159,553	144,485	314,530	225,324
Amortization of Regulatory Assets/(Liabilities), Net	54,574	25,590	108,623	31,016
Amortization of Rate Reduction Bonds	8,082	40,752	42,581	59,100
Energy Efficiency Programs	94,142	73,489	199,913	110,762
Taxes Other Than Income Taxes	123,464	112,862	256,345	198,899
Total Operating Expenses	1,285,286	1,469,169	2,861,364	2,354,399
Operating Income	350,576	159,515	769,521	373,908
Interest Expense:
Interest on Long-Term Debt	85,999	86,925	171,294	146,892
Interest on Rate Reduction Bonds	(189)	2,056	422	3,487
Other Interest	1,040	66	(8,610)	5,116
Total Interest Expense	86,850	89,047	163,106	155,495
Other Income/(Loss), Net	4,944	1,806	12,710	10,580
Income Before Income Tax Expense	268,670	72,274	619,125	228,993
Income Tax Expense	95,606	26,055	216,093	82,019
Net Income	173,064	46,219	403,032	146,974
Net Income Attributable to Noncontrolling Interests	2,043	1,880	3,922	3,373
Net Income Attributable to Controlling Interests	171,021	44,339	399,110	143,601
Diluted Earnings Per Common Share	$ 0.54	$ 0.15	$ 1.26	$ 0.60
Basic Earnings Per Common Share	$ 0.54	$ 0.15	$ 1.27	$ 0.60
Common Stock Dividends Per Share Declared	$ 0.37	$ 0.34	$ 0.74	$ 0.63
Weighted Average Common Shares Outstanding:
Basic	315,154,130	301,047,753	315,141,956	239,551,735
Diluted	315,962,619	301,816,884	315,982,578	240,127,169
The Connecticut Light And Power Company [Member]
Operating Revenues	569,329	562,141	1,193,425	1,154,106
Operating Expenses:
Purchased Power and Transmission	184,854	196,806	414,113	417,697
Operations and Maintenance	123,760	205,471	232,655	338,373
Depreciation	45,122	41,519	87,570	82,588
Amortization of Regulatory Assets/(Liabilities), Net	463	3,263	11,249	11,257
Energy Efficiency Programs	20,854	20,995	43,668	42,968
Taxes Other Than Income Taxes	57,506	53,706	117,697	108,978
Total Operating Expenses	432,559	521,760	906,952	1,001,861
Operating Income	136,770	40,381	286,473	152,245
Interest Expense:
Interest on Long-Term Debt	32,683	31,696	65,318	63,218
Other Interest	1,301	2,075	(1,640)	4,060
Total Interest Expense	33,984	33,771	63,678	67,278
Other Income/(Loss), Net	2,897	447	7,084	5,747
Income Before Income Tax Expense	105,683	7,057	229,879	90,714
Income Tax Expense	37,826	124	77,014	29,796
Net Income	67,857	6,933	152,865	60,918
NSTAR Electric Company [Member]
Operating Revenues	570,420	534,626	1,162,677	1,091,102
Operating Expenses:
Purchased Power and Transmission	189,843	180,502	403,896	399,512
Operations and Maintenance	87,891	109,038	180,192	257,218
Depreciation	45,441	42,669	90,882	85,198
Amortization of Regulatory Assets/(Liabilities), Net	53,554	22,144	100,548	46,024
Amortization of Rate Reduction Bonds	0	22,581	15,054	45,161
Energy Efficiency Programs	50,679	35,487	102,382	82,391
Taxes Other Than Income Taxes	30,491	28,308	62,665	59,169
Total Operating Expenses	457,899	440,729	955,619	974,673
Operating Income	112,521	93,897	207,058	116,429
Interest Expense:
Interest on Long-Term Debt	19,809	22,279	39,401	44,567
Interest on Rate Reduction Bonds	0	927	399	2,253
Other Interest	(2,620)	(5,597)	(6,687)	(11,433)
Total Interest Expense	17,189	17,609	33,113	35,387
Other Income/(Loss), Net	375	6	1,149	1,227
Income Before Income Tax Expense	95,707	76,294	175,094	82,269
Income Tax Expense	37,676	30,812	68,941	32,847
Net Income	58,031	45,482	106,153	49,422
Public Service Company Of New Hampshire [Member]
Operating Revenues	216,113	255,105	489,942	498,102
Operating Expenses:
Purchased Power and Transmission	50,073	82,116	151,097	163,165
Operations and Maintenance	62,400	68,435	122,129	133,413
Depreciation	22,947	21,811	45,515	43,018
Amortization of Regulatory Assets/(Liabilities), Net	1,081	2,798	(1,969)	177
Amortization of Rate Reduction Bonds	4,991	13,814	19,748	27,743
Energy Efficiency Programs	3,376	3,213	7,046	6,794
Taxes Other Than Income Taxes	16,918	15,872	33,932	31,360
Total Operating Expenses	161,786	208,059	377,498	405,670
Operating Income	54,327	47,046	112,444	92,432
Interest Expense:
Interest on Long-Term Debt	10,811	11,539	22,606	23,103
Interest on Rate Reduction Bonds	(239)	786	(154)	1,802
Other Interest	576	460	863	692
Total Interest Expense	11,148	12,785	23,315	25,597
Other Income/(Loss), Net	632	549	1,662	2,590
Income Before Income Tax Expense	43,811	34,810	90,791	69,425
Income Tax Expense	16,617	13,578	34,602	26,931
Net Income	27,194	21,232	56,189	42,494
Western Massachusetts Electric Company [Member]
Operating Revenues	115,015	106,836	239,968	220,861
Operating Expenses:
Purchased Power and Transmission	32,254	32,715	72,298	73,269
Operations and Maintenance	23,136	27,847	44,064	50,449
Depreciation	9,310	6,994	18,280	14,691
Amortization of Regulatory Assets/(Liabilities), Net	685	(44)	814	(387)
Amortization of Rate Reduction Bonds	3,091	4,358	7,780	8,776
Energy Efficiency Programs	7,925	4,933	16,240	10,489
Taxes Other Than Income Taxes	6,206	4,977	12,494	9,858
Total Operating Expenses	82,607	81,780	171,970	167,145
Operating Income	32,408	25,056	67,998	53,716
Interest Expense:
Interest on Long-Term Debt	6,078	5,905	12,032	11,671
Interest on Rate Reduction Bonds	50	343	177	757
Other Interest	148	621	360	836
Total Interest Expense	6,276	6,869	12,569	13,264
Other Income/(Loss), Net	419	188	1,423	1,280
Income Before Income Tax Expense	26,551	18,375	56,852	41,732
Income Tax Expense	10,137	7,237	21,836	16,408
Net Income	$ 16,414	$ 11,138	$ 35,016	$ 25,324