CONSOLIDATED STATEMENT OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities:
Net Income	$ 827,065us-gaap_NetIncomeLoss	$ 793,689us-gaap_NetIncomeLoss	$ 533,077us-gaap_NetIncomeLoss
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	614,657us-gaap_Depreciation	610,777us-gaap_Depreciation	519,010us-gaap_Depreciation
Deferred Income Tax Expense (Benefit)	443,259us-gaap_DeferredIncomeTaxExpenseBenefit	431,413us-gaap_DeferredIncomeTaxExpenseBenefit	292,000us-gaap_DeferredIncomeTaxExpenseBenefit
Pension, SERP and PBOP Expense	99,056	195,698	218,540
Pension and PBOP Contributions	(211,649)	(342,184)	(295,028)
Regulatory Over/(Under) Recoveries, Net	6,853	(24,276)	(259,853)
Amortization of Regulatory Assets/(Liabilities), Net	10,704us-gaap_AmortizationOfRegulatoryAsset	206,322us-gaap_AmortizationOfRegulatoryAsset	79,762us-gaap_AmortizationOfRegulatoryAsset
Amortization of Rate Reduction Bonds	0	42,581	142,019
Proceeds from DOE Damages Claim, Net	132,138nu_ProceedsFromDoeDamagesClaimNet
Other Noncash Income (Expense)	39,523us-gaap_OtherNoncashIncomeExpense	56,071us-gaap_OtherNoncashIncomeExpense	42,852us-gaap_OtherNoncashIncomeExpense
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(122,139)us-gaap_IncreaseDecreaseInReceivables	(163,549)us-gaap_IncreaseDecreaseInReceivables	(20,214)us-gaap_IncreaseDecreaseInReceivables
Increase Decrease in Fuel, Materials and Supplies	(41,310)us-gaap_IncreaseDecreaseInInventories	(14,811)us-gaap_IncreaseDecreaseInInventories	34,321us-gaap_IncreaseDecreaseInInventories
Taxes Receivable/(Accrued)	(323,224)	(50,950)	(5,450)
Accounts Payable	144,743	(54,619)	(128,339)
Other Current Assets and Liabilities	15,797	(22,623)	8,532
Net Cash Flows Provided by Operating Activities	1,635,473	1,663,539	1,161,229
Investing Activities:
Investments in Property, Plant and Equipment	(1,603,744)	(1,456,787)	(1,472,272)
Proceeds from Sales of Marketable Securities	488,789	627,532	317,294
Purchases of Marketable Securities	(491,220)	(679,784)	(348,629)
Other Investing Activities	14,380	67,816	35,683
Net Cash Flows Used in Investing Activities	(1,591,795)	(1,441,223)	(1,467,924)
Financing Activities:
Cash Dividends on Common Stock	(475,227)us-gaap_PaymentsOfDividendsCommonStock	(462,741)us-gaap_PaymentsOfDividendsCommonStock	(375,047)us-gaap_PaymentsOfDividendsCommonStock
Cash Dividends on Preferred Stock	(7,519)	(7,682)	(7,029)
Increase/(Decrease) in Short-Term Debt	285,075	(397,000)	825,000
Issuance of Long-Term Debt	725,000	1,680,000	850,000
Retirements of Long-Term Debt	(576,551)us-gaap_RepaymentsOfLongTermDebt	(929,885)us-gaap_RepaymentsOfLongTermDebt	(839,136)us-gaap_RepaymentsOfLongTermDebt
Retirements of Rate Reduction Bonds	0us-gaap_RepaymentsOfSecuredDebt	(82,139)us-gaap_RepaymentsOfSecuredDebt	(114,433)us-gaap_RepaymentsOfSecuredDebt
Other Financing Activities	883	(25,253)	6,529
Net Cash Flows Provided by/(Used in) Financing Activities	(48,339)	(224,700)	345,884
Net Increase/(Decrease) in Cash	(4,661)	(2,384)	39,189
Cash - Beginning of Year	43,364us-gaap_Cash	45,748us-gaap_Cash	6,559us-gaap_Cash
Cash - End of Year	38,703us-gaap_Cash	43,364us-gaap_Cash	45,748us-gaap_Cash
The Connecticut Light And Power Company [Member]
Operating Activities:
Net Income	287,754	279,412	209,725
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	188,837	177,603	166,853
Deferred Income Tax Expense (Benefit)	130,949	130,038	140,993
Pension, SERP and PBOP Expense	14,992	24,416	24,062
Regulatory Over/(Under) Recoveries, Net	(20,502)	28,298	(100,505)
Amortization of Regulatory Assets/(Liabilities), Net	59,336	4,870	14,372
Proceeds from DOE Damages Claim, Net	68,610
Other Noncash Income (Expense)	(1,342)	(3,478)	(28,952)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(78,631)	(56,593)	(7,741)
Increase Decrease in Fuel, Materials and Supplies	13,063	9,997	(4,573)
Taxes Receivable/(Accrued)	(126,376)	(41,594)	15,702
Accounts Payable	68,891	(66,225)	(190,240)
Other Current Assets and Liabilities	6,838	8,513	(27,803)
Net Cash Flows Provided by Operating Activities	612,419	495,257	211,893
Investing Activities:
Investments in Property, Plant and Equipment	(515,710)	(434,934)	(449,137)
Other Investing Activities	12,653	2,650	32,009
Net Cash Flows Used in Investing Activities	(503,057)	(432,284)	(417,128)
Financing Activities:
Cash Dividends on Common Stock	(171,200)	(151,999)	(100,486)
Cash Dividends on Preferred Stock	(5,559)	(5,559)	(5,559)
Increase/(Decrease) in Short-Term Debt	0	(89,000)	58,000
Issuance of Long-Term Debt	250,000	400,000	0
Increase/(Decrease) in Notes Payable to Affiliate	(153,900)	(117,800)	346,575
Retirements of Long-Term Debt	(150,000)	(125,000)	(116,400)
Capital Contributions from NU Parent	120,000	40,000	25,000
Other Financing Activities	(3,584)	(6,379)	(1,895)
Net Cash Flows Provided by/(Used in) Financing Activities	(114,243)	(55,737)	205,235
Net Increase/(Decrease) in Cash	(4,881)	7,236	0
Cash - Beginning of Year	7,237	1	1
Cash - End of Year	2,356	7,237	1
NSTAR Electric Company [Member]
Operating Activities:
Net Income	303,088	268,546	190,242
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Bad Debt Expense	24,740	28,108	40,301
Depreciation	188,693	180,298	171,070
Deferred Income Tax Expense (Benefit)	108,133	48,808	4,264
Pension, SERP and PBOP Expense	6,760	35,731	66,010
Pension Contribution	(120,306)	(82,000)	(25,000)
Regulatory Over/(Under) Recoveries, Net	57,696	(119,433)	(16,129)
Amortization of Regulatory Assets/(Liabilities), Net	(6,330)	230,148	117,682
Amortization of Rate Reduction Bonds	0	15,054	90,322
Proceeds from DOE Damages Claim, Net	30,193
Other Noncash Income (Expense)	(51,478)	4,428	(32,048)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(18,853)	(45,405)	(10,496)
Increase Decrease in Fuel, Materials and Supplies	(29,943)	3,227	1,813
Taxes Receivable/(Accrued)	(122,746)	(38,003)	29,899
Accounts Payable	9,753	31,875	2,662
Other Current Assets and Liabilities	38,535	(6,468)	22,568
Accounts Payable Related Parties	115,092	(44,491)	(61,879)
Net Cash Flows Provided by Operating Activities	533,027	510,423	591,281
Investing Activities:
Investments in Property, Plant and Equipment	(465,028)	(476,600)	(414,089)
Decrease in Restricted Cash	0	37,604	3,060
Other Investing Activities	0	400	400
Net Cash Flows Used in Investing Activities	(465,028)	(438,596)	(410,629)
Financing Activities:
Cash Dividends on Common Stock	(253,000)	(56,000)	(217,000)
Cash Dividends on Preferred Stock	(1,961)	(2,123)	(1,960)
Increase/(Decrease) in Short-Term Debt	198,500	(172,500)	134,500
Issuance of Long-Term Debt	300,000	200,000	400,000
Retirements of Long-Term Debt	(301,650)	(1,650)	(401,650)
Retirements of Rate Reduction Bonds	0	(43,493)	(84,367)
Other Financing Activities	(5,136)	(1,735)	(5,853)
Net Cash Flows Provided by/(Used in) Financing Activities	(63,247)	(77,501)	(176,330)
Net Increase/(Decrease) in Cash	4,752	(5,674)	4,322
Cash - Beginning of Year	8,021	13,695	9,373
Cash - End of Year	12,773	8,021	13,695
Public Service Company Of New Hampshire [Member]
Operating Activities:
Net Income	113,944	111,397	96,882
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	98,436	91,581	87,602
Deferred Income Tax Expense (Benefit)	94,813	75,693	58,552
Pension, SERP and PBOP Expense	7,197	26,846	26,312
Pension and PBOP Contributions	(2,482)	(112,964)	(96,880)
Regulatory Over/(Under) Recoveries, Net	(11,875)	(8,481)	(183)
Amortization of Regulatory Assets/(Liabilities), Net	(29,602)	(20,387)	(24,086)
Amortization of Rate Reduction Bonds	0	19,748	56,645
Proceeds from DOE Damages Claim, Net	14,453
Other Noncash Income (Expense)	10,095	16,079	11,205
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(15,576)	2,412	(84)
Increase Decrease in Fuel, Materials and Supplies	(19,403)	(33,391)	25,897
Taxes Receivable/(Accrued)	(23,857)	26,462	(9,752)
Accounts Payable	17,796	2,632	(15,248)
Other Current Assets and Liabilities	(5,972)	(9,520)	13,436
Net Cash Flows Provided by Operating Activities	247,967	188,107	230,298
Investing Activities:
Investments in Property, Plant and Equipment	(256,159)	(186,009)	(203,902)
(Increase) Decrease In Notes Receivable From Affiliated Company		0	55,900
Decrease in Restricted Cash	(1,013)	22,040	4,200
Other Investing Activities	(139)	(88)	(135)
Net Cash Flows Used in Investing Activities	(257,311)	(164,057)	(143,937)
Financing Activities:
Cash Dividends on Common Stock	(66,000)	(68,000)	(90,674)
Increase/(Decrease) in Short-Term Debt	4,000	23,200	0
Issuance of Long-Term Debt	75,000	250,000	0
Increase/(Decrease) in Notes Payable to Affiliate	0	0	63,300
Retirements of Long-Term Debt	(50,000)	(198,235)	0
Retirements of Rate Reduction Bonds	0	(29,294)	(56,074)
Capital Contributions from NU Parent	45,000	0	0
Other Financing Activities	1,703	(4,084)	(476)
Net Cash Flows Provided by/(Used in) Financing Activities	9,703	(26,413)	(83,924)
Net Increase/(Decrease) in Cash	359	(2,363)	2,437
Cash - Beginning of Year	130	2,493	56
Cash - End of Year	489	130	2,493
Western Massachusetts Electric Company [Member]
Operating Activities:
Net Income	57,819	60,438	54,503
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	41,886	37,568	29,971
Deferred Income Tax Expense (Benefit)	34,108	87,028	53,942
Regulatory Over/(Under) Recoveries, Net	1,925	8,458	(19,152)
Amortization of Regulatory Assets/(Liabilities), Net	(6,228)	(3,206)	410
Amortization of Rate Reduction Bonds	0	7,780	17,632
Proceeds from DOE Damages Claim, Net	18,883
Other Noncash Income (Expense)	(2,005)	3,381	(3,954)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	39,872	(53,292)	(8,896)
Increase Decrease in Fuel, Materials and Supplies	(627)	865	(2,882)
Taxes Receivable/(Accrued)	(22,454)	19,840	(8,311)
Accounts Payable	1,269	7,456	(19,297)
Other Current Assets and Liabilities	(11,169)	2,491	581
Net Cash Flows Provided by Operating Activities	153,279	178,807	94,547
Investing Activities:
Investments in Property, Plant and Equipment	(116,205)	(128,786)	(264,175)
Proceeds from Sales of Marketable Securities	73,198	70,778	79,769
Purchases of Marketable Securities	(73,888)	(71,390)	(80,529)
(Increase) Decrease In Notes Receivable From Affiliated Company	0	0	11,000
Other Investing Activities	3,200	7,401	(28)
Net Cash Flows Used in Investing Activities	(113,695)	(121,997)	(253,963)
Financing Activities:
Cash Dividends on Common Stock	(59,999)	(40,001)	(9,432)
Issuance of Long-Term Debt	0	80,000	150,000
Increase/(Decrease) in Notes Payable to Affiliate	21,400	(31,900)	31,900
Retirements of Long-Term Debt	0	(55,000)	(53,800)
Retirements of Rate Reduction Bonds	0	(9,352)	(17,540)
Capital Contributions from NU Parent	0	0	50,000
Other Financing Activities	(985)	(558)	8,288
Net Cash Flows Provided by/(Used in) Financing Activities	(39,584)	(56,811)	159,416
Net Increase/(Decrease) in Cash	0	(1)	0
Cash - Beginning of Year		1	1
Cash - End of Year			$ 1

Proceeds from DOE Damages Claim, Net of payments made to non-affiliate member companies

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