CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities:
Net Income	$ 261,338	$ 246,033
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	186,805	173,986
Deferred Income Taxes	141,398	141,132
Pension, SERP and PBOP Expense, Net	5,828	11,583
Pension and PBOP Contributions	(45,700)	(30,383)
Regulatory Over/(Under) Recoveries, Net	56,734	(82,772)
Amortization of Regulatory Assets, Net	24,017	20,997
Other	(42,428)	(16,532)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(50,251)	(133,965)
Fuel, Materials, Supplies and Inventory	(33,058)	(22,748)
Taxes Receivable/Accrued, Net	32,313	279,106
Accounts Payable	(57,701)	(76,317)
Other Current Assets and Liabilities, Net	(42,793)	(10,156)
Net Cash Flows Provided by Operating Activities	436,502	499,964
Investing Activities:
Investments in Property, Plant and Equipment	(523,560)	(431,472)
Proceeds from Sales of Marketable Securities	154,772	136,805
Purchases of Marketable Securities	(149,688)	(135,427)
Other Investing Activities	(11,281)	5,494
Net Cash Flows Used in Investing Activities	(529,757)	(424,600)
Financing Activities:
Cash Dividends on Common Shares	(150,521)	(141,157)
Cash Dividends on Preferred Stock	(1,880)	(1,880)
Decrease in Notes Payable	(173,000)	(391,453)
Issuance of Long-Term Debt	600,000	500,000
Retirements of Long-Term Debt	(150,000)	0
Other Financing Activities	(15,832)	(13,855)
Net Cash Flows Provided by/(Used in) Financing Activities	108,767	(48,345)
Net Increase in Cash and Cash Equivalents	15,512	27,019
Cash and Cash Equivalents - Beginning of Period	30,251	23,947
Cash and Cash Equivalents - End of Period	45,763	50,966
The Connecticut Light And Power Company [Member]
Operating Activities:
Net Income	90,208	87,047
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	59,751	56,969
Deferred Income Taxes	47,864	58,363
Regulatory Over/(Under) Recoveries, Net	(18,734)	(70,195)
Amortization of Regulatory Assets, Net	12,803	9,878
Other	(2,373)	2,216
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(1,280)	(37,501)
Taxes Receivable/Accrued, Net	32,920	141,951
Accounts Payable	(16,957)	(5,040)
Other Current Assets and Liabilities, Net	(32,576)	(22,533)
Net Cash Flows Provided by Operating Activities	171,626	221,155
Investing Activities:
Investments in Property, Plant and Equipment	(181,601)	(147,131)
Proceeds from the Sale of Property, Plant and Equipment	0	9,047
Other Investing Activities	32	49
Net Cash Flows Used in Investing Activities	(181,569)	(138,035)
Financing Activities:
Cash Dividends on Common Shares	(49,600)	(49,900)
Capital Contributions from Eversource Parent	0	145,700
Cash Dividends on Preferred Stock	(1,390)	(1,390)
Decrease in Notes Payable to Eversource Parent	(76,700)	(161,900)
Issuance of Long-Term Debt	300,000	0
Retirements of Long-Term Debt	(150,000)	0
Other Financing Activities	(3,631)	(205)
Net Cash Flows Provided by/(Used in) Financing Activities	18,679	(67,695)
Net Increase in Cash and Cash Equivalents	8,736	15,425
Cash and Cash Equivalents - Beginning of Period	6,579	1,057
Cash and Cash Equivalents - End of Period	15,315	16,482
NSTAR Electric Company [Member]
Operating Activities:
Net Income	66,162	54,493
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	55,216	51,886
Deferred Income Taxes	29,199	32,878
Pension and PBOP Contributions, Net of Pension, SERP and PBOP Expense	(10,422)	(12,953)
Regulatory Over/(Under) Recoveries, Net	4,373	(16,746)
Amortization of Regulatory Assets, Net	4,977	4,683
Other	(3,691)	(3,245)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(2,376)	(29,132)
Fuel, Materials, Supplies and Inventory	(32,050)	(40,322)
Taxes Receivable/Accrued, Net	38,970	33,938
Accounts Payable	(19,025)	1,187
Other Current Assets and Liabilities, Net	2,371	19,600
Net Cash Flows Provided by Operating Activities	133,704	96,267
Investing Activities:
Investments in Property, Plant and Equipment	(132,105)	(91,319)
Other Investing Activities	(3,617)	0
Net Cash Flows Used in Investing Activities	(135,722)	(91,319)
Financing Activities:
Cash Dividends on Common Shares	(46,500)	(90,300)
Cash Dividends on Preferred Stock	(490)	(490)
Decrease in Notes Payable	48,000	86,000
Other Financing Activities	(38)	0
Net Cash Flows Provided by/(Used in) Financing Activities	972	(4,790)
Net Increase in Cash and Cash Equivalents	(1,046)	158
Cash and Cash Equivalents - Beginning of Period	3,494	3,346
Cash and Cash Equivalents - End of Period	2,448	3,504
Public Service Company Of New Hampshire [Member]
Operating Activities:
Net Income	34,312	36,058
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	30,735	28,235
Deferred Income Taxes	11,290	21,181
Regulatory Over/(Under) Recoveries, Net	3,507	(2,291)
Amortization of Regulatory Assets, Net	5,445	8,518
Other	(4,471)	(9,166)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	1,149	(17,207)
Fuel, Materials, Supplies and Inventory	(3,371)	6,903
Taxes Receivable/Accrued, Net	1,778	57,935
Accounts Payable	5,475	2,100
Other Current Assets and Liabilities, Net	27,332	24,021
Net Cash Flows Provided by Operating Activities	113,181	156,287
Investing Activities:
Investments in Property, Plant and Equipment	(75,327)	(72,338)
Other Investing Activities	(145)	84
Net Cash Flows Used in Investing Activities	(75,472)	(72,254)
Financing Activities:
Cash Dividends on Common Shares	(18,500)	(19,400)
Capital Contributions from Eversource Parent	0	11,500
Decrease in Notes Payable to Eversource Parent	(16,000)	(74,200)
Other Financing Activities	(112)	(86)
Net Cash Flows Provided by/(Used in) Financing Activities	(34,612)	(82,186)
Net Increase in Cash and Cash Equivalents	3,097	1,847
Cash and Cash Equivalents - Beginning of Period	4,646	1,733
Cash and Cash Equivalents - End of Period	7,743	3,580
Western Massachusetts Electric Company [Member]
Operating Activities:
Net Income	17,218	16,827
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	12,002	11,371
Deferred Income Taxes	16,176	9,921
Regulatory Over/(Under) Recoveries, Net	(452)	(6,100)
Amortization of Regulatory (Liabilities)/Assets, Net	(488)	1,212
Other	(326)	(541)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(5,924)	2,197
Taxes Receivable/Accrued, Net	(1,404)	26,976
Accounts Payable	(10,141)	(11,011)
Other Current Assets and Liabilities, Net	(4,057)	(136)
Net Cash Flows Provided by Operating Activities	22,604	50,716
Investing Activities:
Investments in Property, Plant and Equipment	(32,744)	(39,891)
Other Investing Activities	9	13
Net Cash Flows Used in Investing Activities	(32,735)	(39,878)
Financing Activities:
Cash Dividends on Common Shares	(9,500)	(9,500)
Decrease in Notes Payable to Eversource Parent	20,400	100
Other Financing Activities	0	(3)
Net Cash Flows Provided by/(Used in) Financing Activities	10,900	(9,403)
Net Increase in Cash and Cash Equivalents	769	1,435
Cash and Cash Equivalents - Beginning of Period	0	834
Cash and Cash Equivalents - End of Period	$ 769	$ 2,269