CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net Income	$ 995,515	$ 949,821	$ 886,004
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities
Depreciation	773,802	715,466	665,856
Deferred Income Taxes	491,630	466,463	491,736
Pension, SERP and PBOP Expense	22,454	39,912	96,017
Pension and PBOP Contributions	(242,800)	(158,741)	(162,452)
Regulatory (Under)/Over Recoveries, Net	(47,935)	13,340	(163,287)
Amortization of Regulatory Assets, Net	89,986	71,696	22,339
Refunds/(Payments) Related to Spent Nuclear Fuel, Net	0	59,804	(297,253)
Other	(148,429)	(77,294)	(82,219)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(117,155)	(142,699)	(39,797)
Fuel, Materials, Supplies and Inventory	(9,223)	7,755	34,112
Taxes Receivable/Accrued, Net	52,284	234,543	30,282
Accounts Payable	56,067	(14,126)	(91,618)
Other Current Assets and Liabilities, Net	88,738	9,112	44,031
Net Cash Flows Provided by Operating Activities	2,004,934	2,175,052	1,433,751
Investing Activities:
Investments in Property, Plant and Equipment	(2,348,105)	(1,976,867)	(1,724,139)
Proceeds from Sales of Marketable Securities	832,903	659,338	799,165
Purchases of Marketable Securities	(810,507)	(681,272)	(717,114)
Acquisition of Aquarion	(877,652)	0	0
Payments to Acquire Investments	(32,634)	(188,958)	(23,353)
Other Investing Activities	25,521	36,951	6,291
Net Cash Flows Used in Investing Activities	(3,210,474)	(2,150,808)	(1,659,150)
Financing Activities:
Cash Dividends on Common Shares	(602,083)	(564,486)	(529,791)
Cash Dividends on Preferred Stock	(7,519)	(7,519)	(7,519)
Increase/(Decrease) in Short-Term Debt	72,810	(12,453)	(242,122)
Issuance of Long-Term Debt	2,500,000	800,000	1,225,000
Retirements of Long-Term Debt	(745,000)	(200,000)	(216,700)
Other Financing Activities	(4,754)	(33,482)	(18,225)
Net Cash Flows Provided by/(Used in) Financing Activities	1,213,454	(17,940)	210,643
Net Increase/(Decrease) in Cash and Cash Equivalents	7,914	6,304	(14,756)
Cash and Cash Equivalents - Beginning of Year	30,251	23,947	38,703
Cash and Cash Equivalents - End of Year	38,165	30,251	23,947
The Connecticut Light And Power Company
Operating Activities:
Net Income	376,726	334,254	299,360
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities
Depreciation	249,352	230,489	215,289
Deferred Income Taxes	119,295	168,919	135,994
Pension, SERP and PBOP Expense	7,409	6,948	14,091
Regulatory (Under)/Over Recoveries, Net	(8,017)	(68,730)	(53,781)
Amortization of Regulatory Assets, Net	83,166	38,765	12,318
Refunds/(Payments) Related to Spent Nuclear Fuel, Net	0	13,568	(242,231)
Other	(37,648)	(32,212)	(36,385)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(47,768)	3,229	(29,195)
Fuel, Materials, Supplies and Inventory	3,612	(8,926)	22,810
Taxes Receivable/Accrued, Net	(9,688)	123,692	(13,517)
Accounts Payable	48,032	3,252	(16,910)
Other Current Assets and Liabilities, Net	20,080	(1,770)	(9,514)
Net Cash Flows Provided by Operating Activities	804,551	811,478	298,329
Investing Activities:
Investments in Property, Plant and Equipment	(824,383)	(611,984)	(523,849)
Proceeds from the Sale of Property, Plant and Equipment	0	9,047	0
Other Investing Activities	236	296	(716)
Net Cash Flows Used in Investing Activities	(824,147)	(602,641)	(524,565)
Financing Activities:
Cash Dividends on Common Shares	(254,800)	(199,599)	(196,000)
Cash Dividends on Preferred Stock	(5,559)	(5,559)	(5,559)
(Decrease)/Increase in Notes Payable to Eversource Parent	(10,600)	(197,300)	144,000
Issuance of Long-Term Debt	525,000	0	350,000
Retirements of Long-Term Debt	(250,000)	0	(162,000)
Capital Contributions from Eversource Parent	0	200,000	105,000
Other Financing Activities	15,004	(857)	(10,504)
Net Cash Flows Provided by/(Used in) Financing Activities	19,045	(203,315)	224,937
Net Increase/(Decrease) in Cash and Cash Equivalents	(551)	5,522	(1,299)
Cash and Cash Equivalents - Beginning of Year	6,579	1,057	2,356
Cash and Cash Equivalents - End of Year	6,028	6,579	1,057
NSTAR Electric Company
Operating Activities:
Net Income	374,726	350,777	401,048
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities
Depreciation	274,008	259,262	240,132
Deferred Income Taxes	110,499	101,698	212,583
Pension, SERP and PBOP Expense	(9,509)	(771)	11,639
Pension and PBOP Contributions	(90,721)	(37,305)	(9,886)
Regulatory (Under)/Over Recoveries, Net	(20,009)	118,385	(141,824)
Amortization of Regulatory Assets, Net	33,831	34,332	1,556
Bad Debt Expense	21,252	31,728	19,168
Refunds/(Payments) Related to Spent Nuclear Fuel, Net	0	8,536	(56,001)
Other	(24,868)	(59,359)	(68,275)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(50,896)	(70,302)	(17,028)
Fuel, Materials, Supplies and Inventory	(24,610)	10,571	19
Taxes Receivable/Accrued, Net	39,205	60,774	62,148
Accounts Payable	(20,421)	18,000	(5,510)
Other Current Assets and Liabilities, Net	25,913	(17,607)	50,283
Net Cash Flows Provided by Operating Activities	638,400	808,719	700,052
Investing Activities:
Investments in Property, Plant and Equipment	(719,623)	(664,932)	(604,018)
Proceeds from Sales of Marketable Securities	3,934	2,479	186,444
Purchases of Marketable Securities	(3,869)	(2,426)	(128,861)
Other Investing Activities	(3,617)	0	0
Net Cash Flows Used in Investing Activities	(723,175)	(664,879)	(546,435)
Financing Activities:
Cash Dividends on Common Shares	(272,000)	(316,300)	(235,200)
Cash Dividends on Preferred Stock	(1,960)	(1,960)	(1,960)
Increase/(Decrease) in Short-Term Debt	56,500	(28,400)	(117,500)
Issuance of Long-Term Debt	700,000	300,000	250,000
Retirements of Long-Term Debt	(400,000)	(200,000)	(54,700)
Capital Contributions from Eversource Parent	2,300	103,000	0
Other Financing Activities	(1,796)	(866)	(2,850)
Net Cash Flows Provided by/(Used in) Financing Activities	83,044	(144,526)	(162,210)
Net Increase/(Decrease) in Cash and Cash Equivalents	(1,731)	(686)	(8,593)
Cash and Cash Equivalents - Beginning of Year	3,494	4,180	12,773
Cash and Cash Equivalents - End of Year	1,763	3,494	4,180
Public Service Company Of New Hampshire
Operating Activities:
Net Income	135,996	131,985	114,442
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities
Depreciation	128,192	116,519	105,372
Deferred Income Taxes	63,883	87,345	83,776
Pension, SERP and PBOP Expense	1,368	875	4,580
Pension and PBOP Contributions	(800)	(17,078)	(982)
Regulatory (Under)/Over Recoveries, Net	(30,788)	(4,491)	41
Amortization of Regulatory Assets, Net	(16,577)	11,170	16,276
Refunds/(Payments) Related to Spent Nuclear Fuel, Net	0	3,926	979
Other	(10,088)	6,521	8,677
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(22,055)	(18,822)	(4,750)
Fuel, Materials, Supplies and Inventory	5,519	(5,485)	(8,729)
Taxes Receivable/Accrued, Net	339	32,303	(23,909)
Accounts Payable	29,453	11,353	(22,203)
Other Current Assets and Liabilities, Net	16,458	5,651	953
Net Cash Flows Provided by Operating Activities	300,900	361,772	274,523
Investing Activities:
Investments in Property, Plant and Equipment	(312,720)	(305,430)	(308,036)
Other Investing Activities	199	326	306
Net Cash Flows Used in Investing Activities	(312,521)	(305,104)	(307,730)
Financing Activities:
Cash Dividends on Common Shares	(23,900)	(77,600)	(106,000)
(Decrease)/Increase in Notes Payable to Eversource Parent	102,000	(70,400)	140,800
Retirements of Long-Term Debt	(70,000)	0	0
Capital Contributions from Eversource Parent	0	94,500	0
Other Financing Activities	(225)	(255)	(349)
Net Cash Flows Provided by/(Used in) Financing Activities	7,875	(53,755)	34,451
Net Increase/(Decrease) in Cash and Cash Equivalents	(3,746)	2,913	1,244
Cash and Cash Equivalents - Beginning of Year	4,646	1,733	489
Cash and Cash Equivalents - End of Year	$ 900	$ 4,646	$ 1,733