CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities:
Net Income	$ 493,966	$ 451,562
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	376,686	350,492
Deferred Income Taxes	269,505	250,851
Pension, SERP and PBOP Expense, Net	11,242	22,659
Pension and PBOP Contributions	(91,400)	(65,929)
Regulatory (Under)/Over Recoveries, Net	85,792	(5,768)
Amortization of Regulatory (Liabilities)/Assets, Net	16,210	12,281
Other	(94,666)	(10,808)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(7,660)	(76,751)
Fuel, Materials, Supplies and Inventory	42,425	43,930
Taxes Receivable/Accrued, Net	23,980	230,075
Accounts Payable	(168,221)	(151,996)
Other Current Assets and Liabilities, Net	(49,889)	(72,160)
Net Cash Flows Provided by Operating Activities	907,970	978,438
Investing Activities:
Investments in Property, Plant and Equipment	(1,146,952)	(869,168)
Proceeds from Sales of Marketable Securities	373,853	327,581
Purchases of Marketable Securities	(394,379)	(322,244)
Other Investing Activities	(11,050)	(2,991)
Net Cash Flows Used in Investing Activities	(1,178,528)	(866,822)
Financing Activities:
Cash Dividends on Common Shares	(301,042)	(282,314)
Cash Dividends on Preferred Stock	(3,759)	(3,759)
Decrease in Notes Payable	(211,000)	(393,953)
Issuance of Long-Term Debt	950,000	800,000
Retirements of Long-Term Debt	(150,000)	(200,000)
Other Financing Activities	(19,254)	(16,811)
Net Cash Flows Provided by/(Used in) Financing Activities	264,945	(96,837)
Net Increase (decrease) in Cash and Cash Equivalents	(5,613)	14,779
Cash and Cash Equivalents - Beginning of Period	30,251	23,947
Cash and Cash Equivalents - End of Period	24,638	38,726
The Connecticut Light And Power Company [Member]
Operating Activities:
Net Income	181,501	169,921
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	120,549	114,500
Deferred Income Taxes	73,277	97,913
Pension, SERP and PBOP (Benefits)/Expense, Net	3,071	3,325
Regulatory (Under)/Over Recoveries, Net	9,762	(40,386)
Amortization of Regulatory (Liabilities)/Assets, Net	24,225	6,891
Other	(27,623)	(4,477)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(22,333)	(26,729)
Taxes Receivable/Accrued, Net	41,733	145,852
Accounts Payable	(63,813)	(38,137)
Other Current Assets and Liabilities, Net	13,541	774
Net Cash Flows Provided by Operating Activities	353,890	429,447
Investing Activities:
Investments in Property, Plant and Equipment	(419,891)	(288,630)
Proceeds from the Sale of Property, Plant and Equipment	0	9,047
Other Investing Activities	132	205
Net Cash Flows Used in Investing Activities	(419,759)	(279,378)
Financing Activities:
Cash Dividends on Common Shares	(99,200)	(99,800)
Capital Contributions from Eversource Parent	0	145,700
Cash Dividends on Preferred Stock	(2,779)	(2,779)
Increase/(Decrease) in Notes Payable to Eversource Parent	21,000	(184,400)
Issuance of Long-Term Debt	300,000	0
Retirements of Long-Term Debt	(150,000)	0
Other Financing Activities	(3,894)	(398)
Net Cash Flows Provided by/(Used in) Financing Activities	65,127	(141,677)
Net Increase (decrease) in Cash and Cash Equivalents	(742)	8,392
Cash and Cash Equivalents - Beginning of Period	6,579	1,057
Cash and Cash Equivalents - End of Period	5,837	9,449
NSTAR Electric Company [Member]
Operating Activities:
Net Income	143,525	122,661
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	111,397	104,457
Deferred Income Taxes	60,673	48,505
Pension and PBOP Contributions	(15,360)	(15,428)
Pension, SERP and PBOP (Benefits)/Expense, Net	(4,944)	2,192
Regulatory (Under)/Over Recoveries, Net	8,257	26,277
Amortization of Regulatory (Liabilities)/Assets, Net	7,961	8,654
Other	(15,309)	(3,978)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(42,050)	(56,140)
Fuel, Materials, Supplies and Inventory	27,221	35,194
Taxes Receivable/Accrued, Net	36,207	45,608
Accounts Payable	(133,614)	(88,774)
Other Current Assets and Liabilities, Net	(45,430)	(64,084)
Net Cash Flows Provided by Operating Activities	138,534	165,144
Investing Activities:
Investments in Property, Plant and Equipment	(262,097)	(199,824)
Other Investing Activities	(3,617)	0
Net Cash Flows Used in Investing Activities	(265,714)	(199,824)
Financing Activities:
Cash Dividends on Common Shares	(93,000)	(278,300)
Capital Contributions from Eversource Parent	1,800	0
Cash Dividends on Preferred Stock	(980)	(980)
Decrease in Notes Payable	(126,500)	266,500
Issuance of Long-Term Debt	350,000	250,000
Retirements of Long-Term Debt	0	(200,000)
Other Financing Activities	(3,159)	(2,495)
Net Cash Flows Provided by/(Used in) Financing Activities	128,161	34,725
Net Increase (decrease) in Cash and Cash Equivalents	981	45
Cash and Cash Equivalents - Beginning of Period	3,494	3,346
Cash and Cash Equivalents - End of Period	4,475	3,391
Public Service Company Of New Hampshire [Member]
Operating Activities:
Net Income	65,903	67,313
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	63,182	56,879
Deferred Income Taxes	37,670	45,976
Regulatory (Under)/Over Recoveries, Net	(1,964)	(10,740)
Amortization of Regulatory (Liabilities)/Assets, Net	(13,492)	332
Other	(6,763)	(8,484)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(1,427)	(5,247)
Fuel, Materials, Supplies and Inventory	12,288	5,394
Taxes Receivable/Accrued, Net	(20,945)	33,840
Accounts Payable	2,236	20,417
Other Current Assets and Liabilities, Net	5,419	(1,422)
Net Cash Flows Provided by Operating Activities	142,107	204,258
Investing Activities:
Investments in Property, Plant and Equipment	(155,737)	(138,713)
Other Investing Activities	26	172
Net Cash Flows Used in Investing Activities	(155,711)	(138,541)
Financing Activities:
Cash Dividends on Common Shares	(23,900)	(38,800)
Capital Contributions from Eversource Parent	0	83,000
Increase/(Decrease) in Notes Payable to Eversource Parent	33,200	(110,400)
Other Financing Activities	(150)	(166)
Net Cash Flows Provided by/(Used in) Financing Activities	9,150	(66,366)
Net Increase (decrease) in Cash and Cash Equivalents	(4,454)	(649)
Cash and Cash Equivalents - Beginning of Period	4,646	1,733
Cash and Cash Equivalents - End of Period	192	1,084
Western Massachusetts Electric Company [Member]
Operating Activities:
Net Income	34,839	30,092
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	24,298	22,847
Deferred Income Taxes	31,549	17,155
Regulatory (Under)/Over Recoveries, Net	1,170	(2,651)
Amortization of Regulatory (Liabilities)/Assets, Net	(849)	2,203
Other	(3,767)	(2,547)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(1,178)	6,500
Taxes Receivable/Accrued, Net	(177)	32,985
Accounts Payable	717	(13,176)
Other Current Assets and Liabilities, Net	(8,942)	2,502
Net Cash Flows Provided by Operating Activities	77,660	95,910
Investing Activities:
Investments in Property, Plant and Equipment	(76,397)	(71,459)
Proceeds from Sales of Marketable Securities	863	1,484
Purchases of Marketable Securities	(826)	(1,457)
Net Cash Flows Used in Investing Activities	(76,360)	(71,432)
Financing Activities:
Cash Dividends on Common Shares	(19,000)	(19,000)
Capital Contributions from Eversource Parent	0	35,000
Increase/(Decrease) in Notes Payable to Eversource Parent	17,700	(89,700)
Issuance of Long-Term Debt	0	50,000
Other Financing Activities	0	(191)
Net Cash Flows Provided by/(Used in) Financing Activities	(1,300)	(23,891)
Net Increase (decrease) in Cash and Cash Equivalents	0	587
Cash and Cash Equivalents - Beginning of Period	0	834
Cash and Cash Equivalents - End of Period	$ 0	$ 1,421