CONSOLIDATED STATEMENT OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities:
Net Income	$ 793,689	$ 533,077	$ 400,513
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	610,777	519,010	302,192
Deferred Income Tax Expense (Benefit)	431,413	292,000	196,761
Pension and PBOP Expense, Net of PBOP Contributions	195,698	218,540	133,000
Pension and Other Postretirement Benefit Contributions	(342,184)	(295,028)	(191,101)
Regulatory (Underrecoveries)/Overrecoveries, Net	(24,276)	(259,853)	(70,863)
Amortization of Regulatory Assets/(Liabilities), Net	206,322	79,762	91,080
Amortization of Rate Reduction Bonds	42,581	142,019	69,912
Other Noncash Income (Expense)	56,071	42,852	(48,772)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(163,549)	(20,214)	17,570
Inventory	(14,811)	34,321	(11,033)
Taxes Receivable/(Accrued)	(50,950)	(5,450)	49,642
Change in Accounts Payable	(54,619)	(128,339)	18,916
Other Current Assets and Liabilities	(22,623)	8,532	12,569
Net Cash Flows Provided by Operating Activities	1,663,539	1,161,229	970,386
Investing Activities:
Investments in Property, Plant and Equipment	(1,456,787)	(1,472,272)	(1,076,730)
Proceeds from Sales of Marketable Securities	627,532	317,294	149,441
Purchases of Marketable Securities	(679,784)	(348,629)	(151,972)
Other Investing Activities	67,816	35,683	60,674
Net Cash Flows Used in Investing Activities	(1,441,223)	(1,467,924)	(1,018,587)
Financing Activities:
Cash Dividends on Common Stock	(462,741)	(375,047)	(194,555)
Cash Dividends on Preferred Stock	(7,682)	(7,029)	(5,559)
Increase/(Decrease) in Short-Term Debt	(397,000)	825,000	50,000
Issuance of Long-Term Debt	1,680,000	850,000	627,500
Retirements of Long-Term Debt	(929,885)	(839,136)	(369,586)
Retirements of Rate Reduction Bonds	(82,139)	(114,433)	(69,312)
Other Financing Activities	(25,253)	6,529	(7,123)
Net Cash Flows Provided by/(Used in) Financing Activities	(224,700)	345,884	31,365
Net Increase/(Decrease) in Cash	(2,384)	39,189	(16,836)
Cash - Beginning of Year	45,748	6,559	23,395
Cash - End of Year	43,364	45,748	6,559
The Connecticut Light And Power Company [Member]
Operating Activities:
Net Income	279,412	209,725	250,164
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	177,603	166,853	157,747
Deferred Income Tax Expense (Benefit)	130,038	140,993	112,620
Pension and PBOP Expense, Net of PBOP Contributions	24,416	24,062	10,664
Regulatory (Underrecoveries)/Overrecoveries, Net	28,298	(100,505)	(82,502)
Amortization of Regulatory Assets/(Liabilities), Net	4,870	14,372	61,025
Other Noncash Income (Expense)	(3,478)	(28,952)	(33,713)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(56,593)	(7,741)	14,610
Inventory	9,997	(4,573)	(2,206)
Taxes Receivable/(Accrued)	(41,594)	15,702	2,719
Change in Accounts Payable	(66,225)	(190,240)	8,864
Other Current Assets and Liabilities	8,513	(27,803)	13,291
Net Cash Flows Provided by Operating Activities	495,257	211,893	513,283
Investing Activities:
Investments in Property, Plant and Equipment	(434,934)	(449,137)	(424,865)
Proceeds From Sale Of Property Plant And Equipment	0		46,841
Other Investing Activities	2,650	32,009	16,001
Net Cash Flows Used in Investing Activities	(432,284)	(417,128)	(362,023)
Financing Activities:
Cash Dividends on Common Stock	(151,999)	(100,486)	(243,218)
Cash Dividends on Preferred Stock	(5,559)	(5,559)	(5,559)
Increase/(Decrease) in Short-Term Debt	(89,000)	58,000	31,000
Issuance of Long-Term Debt	400,000		245,500
Increase/(Decrease) in Notes Payable to Affiliate	(117,800)	346,575	52,300
Retirements of Long-Term Debt	(125,000)	(116,400)	(245,500)
Capital Contributions from NU Parent	40,000	25,000	6,748
Other Financing Activities	(6,379)	(1,895)	(2,292)
Net Cash Flows Provided by/(Used in) Financing Activities	(55,737)	205,235	(161,021)
Net Increase/(Decrease) in Cash	7,236		(9,761)
Cash - Beginning of Year	1	1	9,762
Cash - End of Year	7,237	1	1
NSTAR Electric Company [Member]
Operating Activities:
Net Income	268,546	190,242	252,494
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Bad Debt Expense	28,108	40,301	22,582
Depreciation	180,298	171,070	163,368
Deferred Income Tax Expense (Benefit)	48,808	4,264	72,006
Pension and PBOP Expense, Net of PBOP Contributions	35,731	66,010	54,704
Pension Contribution	(82,000)	(25,000)	(125,000)
Regulatory (Underrecoveries)/Overrecoveries, Net	(119,433)	(16,129)	68,353
Amortization of Regulatory Assets/(Liabilities), Net	230,148	117,682	82,979
Amortization of Rate Reduction Bonds	15,054	90,322	90,322
Other Noncash Income (Expense)	4,428	(32,048)	539
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(45,405)	(10,496)	(26,041)
Inventory	3,227	1,813	(12,968)
Taxes Receivable/(Accrued)	(38,003)	29,899	149,889
Change in Accounts Payable	31,875	2,662	(53,939)
Other Current Assets and Liabilities	(6,468)	22,568	14,272
IncreaseDecreaseInAccountsPayableRelatedParties	(44,491)	(61,879)	(7,232)
Net Cash Flows Provided by Operating Activities	510,423	591,281	746,328
Investing Activities:
Investments in Property, Plant and Equipment	(476,600)	(414,089)	(390,427)
DecreaseInRestrictedCash	37,604	3,060	(2,732)
Other Investing Activities	400	400	6,095
Net Cash Flows Used in Investing Activities	(438,596)	(410,629)	(387,064)
Financing Activities:
Cash Dividends on Common Stock	(56,000)	(217,000)	(169,900)
Cash Dividends on Preferred Stock	(2,123)	(1,960)	(1,960)
Increase/(Decrease) in Short-Term Debt	(172,500)	134,500	(86,000)
Issuance of Long-Term Debt	200,000	400,000	0
Retirements of Long-Term Debt	(1,650)	(401,650)	(16,650)
Retirements of Rate Reduction Bonds	(43,493)	(84,367)	(84,346)
Other Financing Activities	(1,735)	(5,853)	0
Net Cash Flows Provided by/(Used in) Financing Activities	(77,501)	(176,330)	(358,856)
Net Increase/(Decrease) in Cash	(5,674)	4,322	408
Cash - Beginning of Year	13,695	9,373	8,965
Cash - End of Year	8,021	13,695	9,373
Public Service Company Of New Hampshire [Member]
Operating Activities:
Net Income	111,397	96,882	100,267
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	91,581	87,602	76,167
Deferred Income Tax Expense (Benefit)	75,693	58,552	75,628
Pension and PBOP Expense, Net of PBOP Contributions	26,846	26,312	27,298
Pension and Other Postretirement Benefit Contributions	(112,964)	(96,880)	(121,178)
Regulatory (Underrecoveries)/Overrecoveries, Net	(8,481)	(183)	6,079
Amortization of Regulatory Assets/(Liabilities), Net	(20,387)	(24,086)	25,383
Amortization of Rate Reduction Bonds	19,748	56,645	53,389
Changes in Derivative Assets and Liabilities	0	0	(18,072)
Other Noncash Income (Expense)	16,079	11,205	(13,923)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	2,412	(84)	7,833
Inventory	(33,391)	25,897	(9,873)
Taxes Receivable/(Accrued)	26,462	(9,752)	5,139
Change in Accounts Payable	2,632	(15,248)	(4,517)
Other Current Assets and Liabilities	(9,520)	13,436	(4,915)
Net Cash Flows Provided by Operating Activities	188,107	230,298	204,705
Investing Activities:
Investments in Property, Plant and Equipment	(186,009)	(203,902)	(241,772)
(Increase) Decrease In Notes Receivable From Affiliated Company		55,900	(55,900)
DecreaseInRestrictedCash	22,040	4,200	2,223
Other Investing Activities	(88)	(135)	(134)
Net Cash Flows Used in Investing Activities	(164,057)	(143,937)	(295,583)
Financing Activities:
Cash Dividends on Common Stock	(68,000)	(90,674)	(58,828)
Increase/(Decrease) in Short-Term Debt	23,200	0	(30,000)
Issuance of Long-Term Debt	250,000	0	282,000
Increase/(Decrease) in Notes Payable to Affiliate	0	63,300	(47,900)
Retirements of Long-Term Debt	(198,235)	0	(119,800)
Retirements of Rate Reduction Bonds	(29,294)	(56,074)	(52,879)
Capital Contributions from NU Parent	0	0	120,030
Other Financing Activities	(4,084)	(476)	(4,248)
Net Cash Flows Provided by/(Used in) Financing Activities	(26,413)	(83,924)	88,375
Net Increase/(Decrease) in Cash	(2,363)	2,437	(2,503)
Cash - Beginning of Year	2,493	56	2,559
Cash - End of Year	130	2,493	56
Western Massachusetts Electric Company [Member]
Operating Activities:
Net Income	60,438	54,503	43,054
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	37,568	29,971	26,455
Deferred Income Tax Expense (Benefit)	87,028	53,942	23,056
Regulatory (Underrecoveries)/Overrecoveries, Net	8,458	(19,152)	3,328
Amortization of Regulatory Assets/(Liabilities), Net	(3,206)	410	4,492
Amortization of Rate Reduction Bonds	7,780	17,632	16,523
Changes in Derivative Assets and Liabilities	0	0	(6,859)
Other Noncash Income (Expense)	3,381	(3,954)	(586)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(53,292)	(8,896)	(7,263)
Inventory	865	(2,882)	331
Taxes Receivable/(Accrued)	19,840	(8,311)	5,084
Change in Accounts Payable	7,456	(19,297)	12,956
Other Current Assets and Liabilities	2,491	581	3,824
Net Cash Flows Provided by Operating Activities	178,807	94,547	124,395
Investing Activities:
Investments in Property, Plant and Equipment	(128,786)	(264,175)	(237,996)
Proceeds from Sales of Marketable Securities	70,778	79,769	125,157
Purchases of Marketable Securities	(71,390)	(80,529)	(125,453)
(Increase) Decrease In Notes Receivable From Affiliated Company	0	11,000	(11,000)
Other Investing Activities	7,401	(28)	(1,919)
Net Cash Flows Used in Investing Activities	(121,997)	(253,963)	(251,211)
Financing Activities:
Cash Dividends on Common Stock	(40,001)	(9,432)	(26,305)
Issuance of Long-Term Debt	80,000	150,000	100,000
Increase/(Decrease) in Notes Payable to Affiliate	(31,900)	31,900	(20,400)
Retirements of Long-Term Debt	(55,000)	(53,800)	0
Retirements of Rate Reduction Bonds	(9,352)	(17,540)	(16,433)
Capital Contributions from NU Parent	0	50,000	91,812
Other Financing Activities	(558)	8,288	(1,858)
Net Cash Flows Provided by/(Used in) Financing Activities	(56,811)	159,416	126,816
Net Increase/(Decrease) in Cash	(1)	0	0
Cash - Beginning of Year	1	1	1
Cash - End of Year	$ 0	$ 1	$ 1