CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating Revenues	$ 2,513,431	$ 2,290,590
Operating Expenses:
Purchased Power and Transmission	1,162,049	978,150
Operations and Maintenance	333,382	351,688
Depreciation	163,837	150,807
Amortization of Regulatory Assets/(Liabilities), Net	60,604	57,898
Energy Efficiency Programs	146,603	138,825
Taxes Other Than Income Taxes	149,481	145,533
Total Operating Expenses	2,015,956	1,822,901
Operating Income	497,475	467,689
Interest Expense:
Interest on Long-Term Debt	87,714	87,377
Other Interest	7,129	2,598
Total Interest Expense	94,843	89,975
Other Income/(Loss), Net	5,727	1,667
Income Before Income Tax Expense	408,359	379,381
Income Tax Expense	153,226	141,545
Net Income	255,133	237,836
Net Income Attributable to Noncontrolling Interests	1,879	1,879
Net Income Attributable to Controlling Interests	253,254	235,957
Basic Earnings Per Common Share	$ 0.80	$ 0.75
Diluted Earnings Per Common Share	$ 0.80	$ 0.74
Common Stock Dividends Per Share Declared	$ 0.42	$ 0.39
Weighted Average Common Shares Outstanding:
Basic	317,090,841	315,534,512
Diluted	318,491,188	316,892,119
The Connecticut Light And Power Company [Member]
Operating Revenues	804,917	734,614
Operating Expenses:
Purchased Power and Transmission	333,619	281,381
Operations and Maintenance	117,357	109,514
Depreciation	52,902	46,130
Amortization of Regulatory Assets/(Liabilities), Net	48,306	29,931
Energy Efficiency Programs	42,807	42,694
Taxes Other Than Income Taxes	68,080	66,953
Total Operating Expenses	663,071	576,603
Operating Income	141,846	158,011
Interest Expense:
Interest on Long-Term Debt	33,482	32,908
Other Interest	3,142	1,335
Total Interest Expense	36,624	34,243
Other Income/(Loss), Net	2,159	1,072
Income Before Income Tax Expense	107,381	124,840
Income Tax Expense	38,147	45,541
Net Income	69,234	79,299
NSTAR Electric Company [Member]
Operating Revenues	766,808	666,188
Operating Expenses:
Purchased Power and Transmission	401,867	319,082
Operations and Maintenance	75,824	85,924
Depreciation	48,768	46,626
Amortization of Regulatory Assets/(Liabilities), Net	(5,565)	15,664
Energy Efficiency Programs	55,417	48,329
Taxes Other Than Income Taxes	30,962	32,151
Total Operating Expenses	607,273	547,776
Operating Income	159,535	118,412
Interest Expense:
Interest on Long-Term Debt	18,645	20,756
Other Interest	1,801	304
Total Interest Expense	20,446	21,060
Other Income/(Loss), Net	602	(31)
Income Before Income Tax Expense	139,691	97,321
Income Tax Expense	56,130	39,234
Net Income	83,561	58,087
Public Service Company Of New Hampshire [Member]
Operating Revenues	284,847	299,833
Operating Expenses:
Purchased Power and Transmission	99,579	115,246
Operations and Maintenance	58,428	62,212
Depreciation	25,646	24,215
Amortization of Regulatory Assets/(Liabilities), Net	15,132	12,562
Energy Efficiency Programs	3,772	3,839
Taxes Other Than Income Taxes	19,079	17,715
Total Operating Expenses	221,636	235,789
Operating Income	63,211	64,044
Interest Expense:
Interest on Long-Term Debt	11,399	11,526
Other Interest	(127)	445
Total Interest Expense	11,272	11,971
Other Income/(Loss), Net	382	265
Income Before Income Tax Expense	52,321	52,338
Income Tax Expense	20,276	19,700
Net Income	32,045	32,638
Western Massachusetts Electric Company [Member]
Operating Revenues	152,864	137,409
Operating Expenses:
Purchased Power and Transmission	69,661	49,431
Operations and Maintenance	19,784	22,579
Depreciation	10,375	10,321
Amortization of Regulatory Assets/(Liabilities), Net	3,927	399
Energy Efficiency Programs	11,075	11,865
Taxes Other Than Income Taxes	9,437	8,082
Total Operating Expenses	124,259	102,677
Operating Income	28,605	34,732
Interest Expense:
Interest on Long-Term Debt	6,045	6,062
Other Interest	778	(416)
Total Interest Expense	6,823	5,646
Other Income/(Loss), Net	575	574
Income Before Income Tax Expense	22,357	29,660
Income Tax Expense	9,113	11,558
Net Income	$ 13,244	$ 18,102