CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating Revenues	$ 1,995,023	$ 1,099,623
Operating Expenses:
Purchased Power and Transmission	747,809	395,344
Operations and Maintenance	346,092	261,963
Depreciation	154,977	80,839
Amortization of Regulatory Assets/(Liabilities), Net	54,049	5,426
Amortization of Rate Reduction Bonds	34,499	18,347
Energy Efficiency Programs	105,771	37,273
Taxes Other Than Income Taxes	132,881	86,038
Total Operating Expenses	1,576,078	885,230
Operating Income	418,945	214,393
Interest Expense:
Interest on Long-Term Debt	85,295	59,968
Interest on Rate Reduction Bonds	611	1,431
Other Interest	(9,651)	5,048
Total Interest Expense	76,255	66,447
Other Income/(Loss), Net	7,765	8,773
Income Before Income Tax Expense	350,455	156,719
Income Tax Expense	120,487	55,964
Net Income	229,968	100,755
Net Income Attributable to Noncontrolling Interests	1,879	1,493
Net Income Attributable to Controlling Interests	228,089	99,262
Earnings Per Share Basic And Diluted	$ 0.72	$ 0.56
Common Stock Dividends Per Share Declared	$ 0.37	$ 0.29
Weighted Average Common Shares Outstanding:
Basic	315,129,782	178,055,716
Diluted	316,002,538	178,437,453
The Connecticut Light And Power Company [Member]
Operating Revenues	624,097	591,965
Operating Expenses:
Purchased Power and Transmission	229,259	220,891
Operations and Maintenance	108,895	132,902
Depreciation	42,448	41,070
Amortization of Regulatory Assets/(Liabilities), Net	10,787	7,994
Energy Efficiency Programs	22,813	21,973
Taxes Other Than Income Taxes	60,192	55,270
Total Operating Expenses	474,394	480,100
Operating Income	149,703	111,865
Interest Expense:
Interest on Long-Term Debt	32,635	31,521
Other Interest	(2,941)	1,987
Total Interest Expense	29,694	33,508
Other Income/(Loss), Net	4,187	5,300
Income Before Income Tax Expense	124,196	83,657
Income Tax Expense	39,188	29,672
Net Income	85,008	53,985
Public Service Company Of New Hampshire [Member]
Operating Revenues	273,829	242,997
Operating Expenses:
Purchased Power and Transmission	101,024	81,049
Operations and Maintenance	59,729	64,979
Depreciation	22,568	21,208
Amortization of Regulatory Assets/(Liabilities), Net	(3,051)	(2,622)
Amortization of Rate Reduction Bonds	14,756	13,930
Energy Efficiency Programs	3,669	3,581
Taxes Other Than Income Taxes	17,016	15,486
Total Operating Expenses	215,711	197,611
Operating Income	58,118	45,386
Interest Expense:
Interest on Long-Term Debt	11,796	11,563
Interest on Rate Reduction Bonds	85	1,016
Other Interest	287	234
Total Interest Expense	12,168	12,813
Other Income/(Loss), Net	1,030	2,042
Income Before Income Tax Expense	46,980	34,615
Income Tax Expense	17,984	13,353
Net Income	28,996	21,262
Western Massachusetts Electric Company [Member]
Operating Revenues	124,953	114,025
Operating Expenses:
Purchased Power and Transmission	40,044	40,554
Operations and Maintenance	20,928	22,601
Depreciation	8,970	7,697
Amortization of Regulatory Assets/(Liabilities), Net	129	(343)
Amortization of Rate Reduction Bonds	4,689	4,418
Energy Efficiency Programs	8,315	5,556
Taxes Other Than Income Taxes	6,288	4,882
Total Operating Expenses	89,363	85,365
Operating Income	35,590	28,660
Interest Expense:
Interest on Long-Term Debt	5,955	5,766
Interest on Rate Reduction Bonds	127	415
Other Interest	211	214
Total Interest Expense	6,293	6,395
Other Income/(Loss), Net	1,004	1,092
Income Before Income Tax Expense	30,301	23,357
Income Tax Expense	11,698	9,171
Net Income	18,603	14,186
NSTAR Electric Company [Member]
Operating Revenues	592,257	556,476
Operating Expenses:
Purchased Power and Transmission	214,053	219,010
Operations and Maintenance	92,301	148,180
Depreciation	45,441	42,529
Amortization of Regulatory Assets/(Liabilities), Net	46,994	23,880
Amortization of Rate Reduction Bonds	15,054	22,581
Energy Efficiency Programs	51,703	46,904
Taxes Other Than Income Taxes	32,174	30,861
Total Operating Expenses	497,720	533,945
Operating Income	94,537	22,531
Interest Expense:
Interest on Long-Term Debt	19,592	22,288
Interest on Rate Reduction Bonds	399	1,326
Other Interest	(4,068)	(5,836)
Total Interest Expense	15,923	17,778
Other Income/(Loss), Net	773	1,222
Income Before Income Tax Expense	79,387	5,975
Income Tax Expense	31,265	2,035
Net Income	$ 48,122	$ 3,940