Eversource Energy (ES) 10-Q 3 May 18 2018 Q1 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entity [Line Items]
Entity Registrant Name	Eversource Energy
Entity Central Index Key	72,741
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Trading Symbol	ES
Entity Common Stock, Shares Outstanding (in shares)		316,885,808
The Connecticut Light And Power Company
Document And Entity [Line Items]
Entity Registrant Name	The Connecticut Light and Power Company
Entity Central Index Key	23,426
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		6,035,205
Public Service Company Of New Hampshire
Document And Entity [Line Items]
Entity Registrant Name	Public Service Company of New Hampshire
Entity Central Index Key	315,256
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		301
NSTAR Electric Company
Document And Entity [Line Items]
Entity Registrant Name	NSTAR Electric Company
Entity Central Index Key	13,372
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		200

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and Cash Equivalents	$ 303,810,000	$ 38,165,000
Receivables, Net	1,086,282,000	925,083,000
Unbilled Revenues	164,082,000	201,361,000
Fuel, Materials, Supplies and Inventory	264,171,000	223,063,000
Regulatory Assets	683,211,000	741,868,000
Prepayments and Other Current Assets	210,534,000	138,009,000
Assets Held for Sale	59,346,000	219,550,000
Total Current Assets	2,771,436,000	2,487,099,000
Property, Plant and Equipment, Net	23,958,688,000	23,617,463,000
Deferred Debits and Other Assets:
Regulatory Assets	4,655,521,000	4,497,447,000
Goodwill	4,427,266,000	4,427,266,000
Marketable Securities	580,446,000	585,419,000
Other Long-Term Assets	646,626,000	605,692,000
Total Deferred Debits and Other Assets	10,309,859,000	10,115,824,000
Total Assets	37,039,983,000	36,220,386,000
Current Liabilities:
Notes Payable	1,049,305,000	1,088,087,000
Notes Payable to Eversource Parent	276,300,000	115,900,000
Long-Term Debt – Current Portion	1,097,288,000	549,631,000
Accounts Payable	984,343,000	1,085,034,000
Regulatory Liabilities	205,970,000	128,071,000
Other Current Liabilities	759,112,000	738,222,000
Total Current Liabilities	4,096,018,000	3,589,045,000
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	3,389,606,000	3,297,518,000
Regulatory Liabilities	3,703,735,000	3,637,273,000
Derivative Liabilities	415,402,000	377,257,000
Accrued Pension, SERP and PBOP	1,026,181,000	1,228,091,000
Other Long-Term Liabilities	1,053,765,000	1,073,501,000
Total Deferred Credits and Other Liabilities	9,588,689,000	9,613,640,000
Capitalization:
Long-Term Debt	12,015,992,000	11,775,889,000
Noncontrolling Interest – Preferred Stock of Subsidiaries	155,570,000	155,570,000
Common Shareholders' Equity:
Common Shares	1,669,392,000	1,669,392,000
Capital Surplus, Paid In	6,224,620,000	6,239,940,000
Retained Earnings	3,670,603,000	3,561,084,000
Accumulated Other Comprehensive Loss	(63,130,000)	(66,403,000)
Treasury Stock	(317,771,000)	(317,771,000)
Common Stockholder's Equity	11,183,714,000	11,086,242,000
Total Capitalization	23,355,276,000	23,017,701,000
Total Liabilities and Capitalization	37,039,983,000	36,220,386,000
The Connecticut Light And Power Company
Current Assets:
Cash and Cash Equivalents	240,217,000	6,028,000
Receivables, Net	411,437,000	370,676,000
Accounts Receivable from Affiliated Companies	29,122,000	28,181,000
Unbilled Revenues	48,763,000	54,154,000
Materials, Supplies and Inventory	53,637,000	48,438,000
Regulatory Assets	229,735,000	200,281,000
Prepayments and Other Current Assets	56,413,000	46,926,000
Total Current Assets	1,069,324,000	754,684,000
Property, Plant and Equipment, Net	8,406,595,000	8,271,030,000
Deferred Debits and Other Assets:
Regulatory Assets	1,499,588,000	1,444,935,000
Other Long-Term Assets	171,092,000	159,597,000
Total Deferred Debits and Other Assets	1,670,680,000	1,604,532,000
Total Assets	11,146,599,000	10,630,246,000
Current Liabilities:
Notes Payable to Eversource Parent	0	69,500,000
Long-Term Debt – Current Portion	550,000,000	300,000,000
Accounts Payable	346,676,000	367,605,000
Accounts Payable to Affiliated Companies	90,481,000	82,201,000
Regulatory Liabilities	66,949,000	38,967,000
Other Current Liabilities	264,064,000	234,486,000
Total Current Liabilities	1,318,170,000	1,092,759,000
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,133,045,000	1,103,367,000
Regulatory Liabilities	1,136,361,000	1,112,136,000
Derivative Liabilities	415,036,000	376,918,000
Accrued Pension, SERP and PBOP	266,824,000	354,469,000
Other Long-Term Liabilities	124,056,000	128,135,000
Total Deferred Credits and Other Liabilities	3,075,322,000	3,075,025,000
Capitalization:
Long-Term Debt	3,003,562,000	2,759,135,000
Noncontrolling Interest – Preferred Stock of Subsidiaries	116,200,000	116,200,000
Common Shareholders' Equity:
Common Shares	60,352,000	60,352,000
Capital Surplus, Paid In	2,119,765,000	2,110,765,000
Retained Earnings	1,452,919,000	1,415,741,000
Accumulated Other Comprehensive Loss	309,000	269,000
Common Stockholder's Equity	3,633,345,000	3,587,127,000
Total Capitalization	6,753,107,000	6,462,462,000
Total Liabilities and Capitalization	11,146,599,000	10,630,246,000
NSTAR Electric Company
Current Assets:
Cash and Cash Equivalents	9,471,000	1,763,000
Receivables, Net	406,599,000	341,341,000
Accounts Receivable from Affiliated Companies	26,335,000	40,723,000
Unbilled Revenues	41,213,000	49,865,000
Fuel, Materials, Supplies and Inventory	132,943,000	95,517,000
Regulatory Assets	276,962,000	333,882,000
Prepayments and Other Current Assets	42,250,000	24,499,000
Total Current Assets	935,773,000	887,590,000
Property, Plant and Equipment, Net	8,323,826,000	8,246,494,000
Deferred Debits and Other Assets:
Regulatory Assets	1,287,282,000	1,190,575,000
Prepaid PBOP	133,650,000	126,948,000
Other Long-Term Assets	86,898,000	84,766,000
Total Deferred Debits and Other Assets	1,507,830,000	1,402,289,000
Total Assets	10,767,429,000	10,536,373,000
Current Liabilities:
Notes Payable	367,000,000	234,000,000
Notes Payable to Eversource Parent		198,000,000
Accounts Payable	329,558,000	340,115,000
Accounts Payable to Affiliated Companies	137,132,000	91,260,000
Obligations to Third Party Suppliers	101,654,000	88,721,000
Renewable Portfolio Standards Compliance Obligations	139,174,000	111,524,000
Regulatory Liabilities	89,230,000	79,562,000
Other Current Liabilities	57,333,000	79,916,000
Total Current Liabilities	1,221,081,000	1,025,098,000
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,297,365,000	1,275,814,000
Regulatory Liabilities	1,530,103,000	1,514,451,000
Accrued Pension, SERP and PBOP	80,248,000	89,995,000
Other Long-Term Liabilities	197,371,000	198,176,000
Total Deferred Credits and Other Liabilities	3,105,087,000	3,078,436,000
Capitalization:
Long-Term Debt	2,943,915,000	2,943,759,000
Noncontrolling Interest – Preferred Stock of Subsidiaries	43,000,000	43,000,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,595,442,000	1,502,942,000
Retained Earnings	1,860,621,000	1,944,961,000
Accumulated Other Comprehensive Loss	(1,717,000)	(1,823,000)
Common Stockholder's Equity	3,454,346,000	3,446,080,000
Total Capitalization	6,441,261,000	6,432,839,000
Total Liabilities and Capitalization	10,767,429,000	10,536,373,000
Public Service Company Of New Hampshire
Current Assets:
Cash and Cash Equivalents	2,917,000	900,000
Receivables, Net	94,179,000	92,774,000
Accounts Receivable from Affiliated Companies	10,253,000	5,297,000
Unbilled Revenues	41,444,000	49,448,000
Taxes Receivable	34,871,000	5,838,000
Fuel, Materials, Supplies and Inventory	49,582,000	40,285,000
Regulatory Assets	122,481,000	130,134,000
Prepayments and Other Current Assets	15,918,000	23,093,000
Assets Held for Sale	59,346,000	219,550,000
Total Current Assets	430,991,000	567,319,000
Property, Plant and Equipment, Net	2,693,951,000	2,642,274,000
Deferred Debits and Other Assets:
Regulatory Assets	816,194,000	810,677,000
Other Long-Term Assets	53,656,000	42,391,000
Total Deferred Debits and Other Assets	869,850,000	853,068,000
Total Assets	3,994,792,000	4,062,661,000
Current Liabilities:
Notes Payable to Eversource Parent	271,300,000	262,900,000
Long-Term Debt – Current Portion	110,000,000	110,000,000
Accounts Payable	94,498,000	128,685,000
Accounts Payable to Affiliated Companies	33,828,000	24,676,000
Dividends Payable to Eversource Parent	0	150,000,000
Renewable Portfolio Standards Compliance Obligations	35,447,000	27,765,000
Regulatory Liabilities	15,607,000	6,251,000
Other Current Liabilities	59,876,000	40,159,000
Total Current Liabilities	620,556,000	750,436,000
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	490,487,000	443,468,000
Regulatory Liabilities	449,588,000	444,397,000
Accrued Pension, SERP and PBOP	121,414,000	124,639,000
Other Long-Term Liabilities	34,990,000	56,689,000
Total Deferred Credits and Other Liabilities	1,096,479,000	1,069,193,000
Capitalization:
Long-Term Debt	891,801,000	892,438,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	843,134,000	843,134,000
Retained Earnings	546,475,000	511,382,000
Accumulated Other Comprehensive Loss	(3,653,000)	(3,922,000)
Common Stockholder's Equity	1,385,956,000	1,350,594,000
Total Capitalization	2,277,757,000	2,243,032,000
Total Liabilities and Capitalization	$ 3,994,792,000	$ 4,062,661,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Revenues	$ 2,287,962	$ 2,105,135
Operating Expenses:
Purchased Power, Fuel and Transmission	946,747	753,649
Operations and Maintenance	332,549	338,307
Depreciation	204,266	186,805
Amortization	45,194	24,017
Energy Efficiency Programs	134,241	146,158
Taxes Other Than Income Taxes	182,433	155,222
Total Operating Expenses	1,845,430	1,604,158
Operating Income/(Loss)	442,532	500,977
Interest Expense	121,129	103,429
Other Income, Net	33,789	21,619
Income Before Income Tax Expense	355,192	419,167
Income Tax Expense	83,766	157,829
Net Income	271,426	261,338
Net Income Attributable to Noncontrolling Interests	1,880	1,880
Net Income Attributable to Common Shareholders	$ 269,546	$ 259,458
Basic and Diluted Earnings Per Common Share (in dollars per share)	$ 0.85	$ 0.82
Dividends Declared Per Common Share (in dollars per share)	$ 0.51	$ 0.48
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,397,052	317,463,151
Diluted (in shares)	317,992,999	318,124,536
The Connecticut Light And Power Company
Operating Revenues	$ 784,983	$ 732,310
Operating Expenses:
Purchased Power, Fuel and Transmission	301,889	244,938
Operations and Maintenance	117,292	128,737
Depreciation	67,498	59,751
Amortization	28,006	12,803
Energy Efficiency Programs	22,760	36,591
Taxes Other Than Income Taxes	90,300	73,979
Total Operating Expenses	627,745	556,799
Operating Income/(Loss)	157,238	175,511
Interest Expense	36,823	34,964
Other Income, Net	6,560	3,267
Income Before Income Tax Expense	126,975	143,814
Income Tax Expense	28,407	53,606
Net Income	98,568	90,208
NSTAR Electric Company
Operating Revenues	770,127	733,808
Operating Expenses:
Purchased Power, Fuel and Transmission	332,579	273,852
Operations and Maintenance	118,682	115,872
Depreciation	70,542	67,218
Amortization	6,364	4,489
Energy Efficiency Programs	74,793	77,976
Taxes Other Than Income Taxes	48,186	37,821
Total Operating Expenses	651,146	577,228
Operating Income/(Loss)	118,981	156,580
Interest Expense	26,464	28,279
Other Income, Net	12,601	8,349
Income Before Income Tax Expense	105,118	136,650
Income Tax Expense	27,969	53,269
Net Income	77,149	83,381
Public Service Company Of New Hampshire
Operating Revenues	267,350	253,157
Operating Expenses:
Purchased Power, Fuel and Transmission	109,717	61,747
Operations and Maintenance	51,380	63,964
Depreciation	23,493	30,735
Amortization	5,035	5,445
Energy Efficiency Programs	5,157	3,746
Taxes Other Than Income Taxes	16,801	20,881
Total Operating Expenses	211,583	186,518
Operating Income/(Loss)	55,767	66,639
Interest Expense	12,772	12,808
Other Income, Net	4,749	2,811
Income Before Income Tax Expense	47,744	56,642
Income Tax Expense	12,651	22,330
Net Income	$ 35,093	$ 34,312

CONDENSED CONSOLIDATED STATEME4

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net Income	$ 271,426	$ 261,338
Other Comprehensive (Loss)/Income, Net of Tax:
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	2,993	962
Qualified Cash Flow Hedging Instruments	724	534
Changes in Unrealized (Losses)/Gains on Marketable	(444)	1,645
Net OCI	3,273	3,141
Comprehensive Income Attributable to Noncontrolling Interests	(1,880)	(1,880)
Comprehensive Income Attributable to Common Shareholders	272,819	262,599
The Connecticut Light And Power Company
Net Income	98,568	90,208
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	52	111
Changes in Unrealized (Losses)/Gains on Marketable	(12)	56
Net OCI	40	167
Comprehensive Income Attributable to Common Shareholders	98,608	90,375
NSTAR Electric Company
Net Income	77,149	83,381
Other Comprehensive (Loss)/Income, Net of Tax:
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	1	(4)
Qualified Cash Flow Hedging Instruments	109	109
Changes in Unrealized (Losses)/Gains on Marketable	(4)	16
Net OCI	106	121
Comprehensive Income Attributable to Common Shareholders	77,255	83,502
Public Service Company Of New Hampshire
Net Income	35,093	34,312
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	290	291
Changes in Unrealized (Losses)/Gains on Marketable	(21)	97
Net OCI	269	388
Comprehensive Income Attributable to Common Shareholders	$ 35,362	$ 34,700

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities:
Net Income	$ 271,426	$ 261,338
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	204,266	186,805
Deferred Income Taxes	88,481	141,398
Pension, SERP and PBOP (Income)/Expense, Net	(1,965)	5,828
Pension and PBOP Contributions	(171,244)	(45,700)
Regulatory Overrecoveries, Net	70,457	56,734
Amortization of Regulatory Assets, Net	45,194	24,017
Other	(54,969)	(36,176)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(156,888)	(50,251)
Fuel, Materials, Supplies and Inventory	(26,956)	(33,058)
Taxes Receivable/Accrued, Net	(5,061)	32,313
Accounts Payable	(61,571)	(57,701)
Other Current Assets and Liabilities, Net	(23,456)	(40,198)
Net Cash Flows Provided by Operating Activities	177,714	445,349
Investing Activities:
Investments in Property, Plant and Equipment	(607,334)	(523,560)
Proceeds from Sales of Marketable Securities	145,438	154,772
Purchases of Marketable Securities	(143,264)	(149,688)
Proceeds from the Sale of Property, Plant and Equipment	130,641	0
Other Investing Activities	(5,200)	(16,105)
Net Cash Flows Used in Investing Activities	(479,719)	(534,581)
Financing Activities:
Cash Dividends on Common Shares	(160,027)	(150,521)
Cash Dividends on Preferred Stock	(1,880)	(1,880)
Decrease in Notes Payable	(240,005)	(173,000)
Issuance of Long-Term Debt	1,150,000	600,000
Retirements of Long-Term Debt	(150,218)	(150,000)
Other Financing Activities	(19,140)	(15,832)
Net Cash Flows Provided by Financing Activities	578,730	108,767
Net Increase in Cash, Cash Equivalents and Restricted Cash	276,725	19,535
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	85,890	106,750
Cash, Cash Equivalents and Restricted Cash - End of Period	362,615	126,285
The Connecticut Light And Power Company
Operating Activities:
Net Income	98,568	90,208
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	67,498	59,751
Deferred Income Taxes	29,109	47,864
Pension, SERP and PBOP (Income)/Expense, Net	(82,276)	(625)
Regulatory Overrecoveries, Net	(8,878)	(18,734)
Amortization of Regulatory Assets, Net	28,006	12,803
Other	(11,870)	(1,710)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(46,330)	(1,280)
Taxes Receivable/Accrued, Net	42,460	32,920
Accounts Payable	(28,408)	(16,957)
Other Current Assets and Liabilities, Net	(23,160)	(30,823)
Net Cash Flows Provided by Operating Activities	64,719	173,417
Investing Activities:
Investments in Property, Plant and Equipment	(202,126)	(181,601)
Other Investing Activities	56	32
Net Cash Flows Used in Investing Activities	(202,070)	(181,569)
Financing Activities:
Cash Dividends on Common Shares	(60,000)	(49,600)
Capital Contributions from Eversource Parent	9,000	0
Cash Dividends on Preferred Stock	(1,390)	(1,390)
Increase/(Decrease) in Notes Payable to Eversource Parent	(69,500)	(76,700)
Issuance of Long-Term Debt	500,000	300,000
Retirements of Long-Term Debt	0	(150,000)
Other Financing Activities	(6,539)	(3,631)
Net Cash Flows Provided by Financing Activities	371,571	18,679
Net Increase in Cash, Cash Equivalents and Restricted Cash	234,220	10,527
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	9,619	8,403
Cash, Cash Equivalents and Restricted Cash - End of Period	243,839	18,930
NSTAR Electric Company
Operating Activities:
Net Income	77,149	83,381
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	70,542	67,218
Deferred Income Taxes	22,542	45,375
Pension, SERP and PBOP Benefits, Net	(9,295)	(10,548)
Regulatory Overrecoveries, Net	17,618	3,921
Amortization of Regulatory Assets, Net	6,364	4,489
Other	(2,204)	(3,877)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(52,949)	(9,275)
Fuel, Materials, Supplies and Inventory	(37,427)	(33,342)
Taxes Receivable/Accrued, Net	(22,698)	37,566
Accounts Payable	43,170	(29,015)
Other Current Assets and Liabilities, Net	23,703	1,251
Net Cash Flows Provided by Operating Activities	136,515	157,144
Investing Activities:
Investments in Property, Plant and Equipment	(192,036)	(164,849)
Other Investing Activities	(654)	(3,608)
Net Cash Flows Used in Investing Activities	(192,690)	(168,457)
Financing Activities:
Cash Dividends on Common Shares	(161,000)	(56,000)
Capital Contributions from Eversource Parent	92,500	0
Cash Dividends on Preferred Stock	(490)	(490)
Decrease in Notes Payable	133,000	68,400
Other Financing Activities	(78)	(38)
Net Cash Flows Provided by Financing Activities	63,932	11,872
Net Increase in Cash, Cash Equivalents and Restricted Cash	7,757	559
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	14,708	15,506
Cash, Cash Equivalents and Restricted Cash - End of Period	22,465	16,065
Public Service Company Of New Hampshire
Operating Activities:
Net Income	35,093	34,312
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	23,493	30,735
Deferred Income Taxes	43,021	11,290
Regulatory Overrecoveries, Net	129	3,507
Amortization of Regulatory Assets, Net	5,035	5,445
Other	(15,212)	(4,405)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(80)	1,149
Fuel, Materials, Supplies and Inventory	4,854	(3,371)
Taxes Receivable/Accrued, Net	(5,867)	1,778
Accounts Payable	(18,760)	5,475
Other Current Assets and Liabilities, Net	24,543	27,332
Net Cash Flows Provided by Operating Activities	96,249	113,247
Investing Activities:
Investments in Property, Plant and Equipment	(72,287)	(75,327)
Proceeds from the Sale of Property, Plant and Equipment	130,641	0
Other Investing Activities	97	(145)
Net Cash Flows Used in Investing Activities	58,451	(75,472)
Financing Activities:
Cash Dividends on Common Shares	(150,000)	(18,500)
Increase/(Decrease) in Notes Payable to Eversource Parent	8,400	(16,000)
Other Financing Activities	(38)	(112)
Net Cash Flows Provided by Financing Activities	(141,638)	(34,612)
Net Increase in Cash, Cash Equivalents and Restricted Cash	13,062	3,163
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	2,191	5,953
Cash, Cash Equivalents and Restricted Cash - End of Period	$ 15,253	$ 9,116

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES A. Basis of Presentation Eversource Energy is a public utility holding company primarily engaged, through its wholly-owned regulated utility subsidiaries, in the energy delivery business. Eversource Energy's wholly-owned regulated utility subsidiaries consist of CL&P, NSTAR Electric and PSNH (electric utilities), Yankee Gas and NSTAR Gas (natural gas utilities) and Aquarion (water utilities). Eversource provides energy delivery and/or water service to approximately four million electric, natural gas and water customers through eight regulated utilities in Connecticut, Massachusetts and New Hampshire. On December 31, 2017, Western Massachusetts Electric Company ("WMECO") was merged into NSTAR Electric. In accordance with accounting guidance on combinations between entities under common control, the net assets, results of operations and cash flows of WMECO are reflected in the NSTAR Electric financial statements. NSTAR Electric's financial statements for all prior periods presented in this combined Quarterly Report on Form 10-Q have been retrospectively recast as if the merger occurred on the first day of the earliest reporting period. The unaudited condensed consolidated financial statements of Eversource, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements of Eversource, NSTAR Electric and PSNH and the unaudited condensed financial statements of CL&P are herein collectively referred to as the "financial statements." The combined notes to the financial statements have been prepared pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures included in annual financial statements prepared in accordance with GAAP have been omitted pursuant to such rules and regulations. The accompanying financial statements should be read in conjunction with the Combined Notes to Financial Statements included in Item 8, "Financial Statements and Supplementary Data," of the Eversource 2017 Form 10-K, which was filed with the SEC on February 26, 2018. The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The financial statements contain, in the opinion of management, all adjustments (including normal, recurring adjustments) necessary to present fairly Eversource's, CL&P's, NSTAR Electric's and PSNH's financial position as of March 31, 2018 and December 31, 2017 , and the results of operations, comprehensive income and cash flows for the three months ended March 31, 2018 and 2017 . The results of operations, comprehensive income and cash flows for the three months ended March 31, 2018 and 2017 are not necessarily indicative of the results expected for a full year. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership interest in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource's utility subsidiaries' electric and natural gas distribution (including generation assets), transmission and water distribution businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. Certain reclassifications of prior period data were made in the accompanying financial statements to conform to the current period presentation. On December 22, 2017, the Tax Cuts and Jobs Act became law, which amended existing federal tax rules and included numerous provisions that impacted corporations. In particular, this act reduced the U.S. federal corporate income tax rate from 35 percent to 21 percent effective January 1, 2018. Our regulated companies have established a reserve in revenue to reflect the difference between the 35 percent federal corporate income tax rate included in rates charged to customers and the 21 percent federal income tax rate. Eversource, CL&P, NSTAR Electric and PSNH's effective tax rate has decreased, as compared to the prior period, as a result of incurring a lower federal income tax expense, which is reflected on the statements of income as of March 31, 2018 . See Note 15, "Revenues," for further information on the amounts reserved in revenues. B. Accounting Standards Accounting Standards Issued but Not Yet Effective: In February 2016, the FASB issued Accounting Standards Update ("ASU") 2016-02, Leases , which changes existing lease accounting guidance and is required to be applied in the first quarter of 2019, with earlier application permitted. The ASU lease criteria are required to be applied to leases and lease renewals entered into effective January 1, 2019. The Company will implement the ASU in the first quarter of 2019. The requirements of the ASU include balance sheet recognition of leases previously deemed to be operating leases, and additional disclosure requirements. The Company is in the process of evaluating what impact the ASU will have on its financial statements. As of December 31, 2017, Eversource’s total future undiscounted minimum rental payments, excluding executory costs, under long-term noncancelable operating and capital leases were less than $100 million . Accounting Standards Recently Adopted: On January 1, 2018, Eversource, CL&P, NSTAR Electric and PSNH adopted ASU 2014-09, Revenue from Contracts with Customers , which amended existing revenue recognition guidance, using the modified retrospective method (cumulatively at the date of initial application) applying it only to contracts that were not complete at January 1, 2018. Under this method of adoption, prior year reported results were not restated. Implementation of the ASU did not have a material effect on the results of operations, financial position or cash flows of Eversource, CL&P, NSTAR Electric or PSNH. See Note 15, "Revenues," for further information . The Company identified an item that was accounted for differently under the new revenue guidance, as compared to the previously existing guidance. As a result of applying guidance on the unit of account under the new standard, purchases of power from and sales of power to ISO-New England are now accounted for net by the hour, rather than net by the month. This change increased Operating Revenues and Purchased Power, Fuel and Transmission by $19 million for the three months ended March 31, 2018, with no impact on net income. On January 1, 2018, Eversource adopted ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Liabilities . The ASU removed the available-for-sale designation for equity securities, whereby changes in fair value were previously recorded in accumulated other comprehensive income within shareholders' equity, and required changes in fair value of all equity securities to be recorded in earnings effective January 1, 2018. There was no cumulative effect of adoption. For the three months ended March 31, 2018, unrealized losses recorded in Other Income, Net were $0.7 million . For further information, see Note 5, "Marketable Securities," to the financial statements. On January 1, 2018, Eversource, CL&P, NSTAR Electric and PSNH adopted ASU 2017-07, Compensation – Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The ASU required separate presentation of service cost from other components of net pension and PBOP costs, with the other components presented as non-operating income and not subject to capitalization. The ASU has been applied retrospectively for the separate presentation in the income statement of service costs and other components and prospectively in the balance sheet for the capitalization of only the service cost component. As of March 31, 2018, the non-service cost components of net pension, SERP and PBOP costs that were not capitalized in plant were recorded as an increase to regulatory liabilities of approximately $10 million , as these amounts continue to be included in rates. See Note 1F, "Summary of Significant Accounting Policies - Other Income, Net," to the financial statements for the portion of pension and PBOP costs that are presented as non-operating income for the three months ended March 31, 2018 and 2017. The March 31, 2017 amounts, which were previously presented within Operations and Maintenance expense on the statements of income, totaled $8.0 million at Eversource, $0.5 million at CL&P, $5.0 million at NSTAR Electric and $1.6 million at PSNH, and have been retrospectively presented to Other Income, Net. On January 1, 2018, Eversource, CL&P, NSTAR Electric and PSNH adopted two accounting standards relating to the statement of cash flows; ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments, and ASU 2016-18, Restricted Cash. As a result of implementing ASU 2016-15, dividends from equity method investments of $6.2 million and $4.8 million in the first quarter of 2018 and 2017, respectively, are presented in operating activities at Eversource, for which the 2017 amounts were previously classified in investing activities. ASU 2016-18 required that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash and restricted cash equivalents. Both standards were applied retrospectively, as required, and neither had a material impact on Eversource's, CL&P's, NSTAR Electric's or PSNH's statements of cash flows. See Note 1H, "Summary of Significant Accounting Policies - Supplemental Cash Flow Information," to the financial statements for a reconciliation of cash and cash equivalents as reported on the balance sheet to the statement of cash flows, which includes amounts described as restricted cash and restricted cash equivalents. C. Northern Pass Northern Pass is Eversource's planned 1,090 MW HVDC transmission line that will interconnect from the Québec-New Hampshire border to Franklin, New Hampshire and an associated alternating current radial transmission line between Franklin and Deerfield, New Hampshire. As of March 31, 2018, our capitalized Northern Pass project costs were approximately $289 million . In March 2018, the Massachusetts EDCs terminated contract negotiations with and conditional selection of Northern Pass under the Massachusetts Clean Energy RFP, and the New Hampshire Site Evaluation Committee ("NHSEC") issued a written decision denying Northern Pass’ siting application. NPT reviewed the written decision and filed a motion for rehearing with the NHSEC on April 27, 2018. The NHSEC denial of Northern Pass' siting application caused us to review the recoverability of our Northern Pass project costs. In this recoverability review, we estimated undiscounted expected project cash flows and compared the result to our estimated project costs to determine whether the recorded amount is recoverable. Our undiscounted cash flows were substantially in excess of our estimated project costs. We completed this analysis and concluded that our project costs are recoverable based on our expectation that the Northern Pass project remains probable of being placed in service. Consistent with Eversource’s and HQ’s long-term relationship to bring clean energy into New England, Eversource and HQ remain committed to Northern Pass and the many benefits this project will bring to our customers and the region. If as a result of future events and changes in circumstances a new recoverability review were to conclude that our project costs are not recoverable, then we would reduce Northern Pass' project costs to the estimated fair value, which could result in most of our $289 million of capitalized project costs being written off. Such a write off could have a material adverse effect on our financial position and results of operations. D. Provision for Uncollectible Accounts Eversource, including CL&P, NSTAR Electric and PSNH, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectability from customers. Management continuously assesses the collectability of receivables and adjusts collectability estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the customer accounts are terminated and these balances are deemed to be uncollectible. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric and NSTAR Gas to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. These uncollectible hardship customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets. The total provision for both uncollectible accounts and for uncollectible hardship accounts (the uncollectible hardship balance is included in the total provision) is included in Receivables, Net on the balance sheets, and is as follows: Total Provision for Uncollectible Accounts Uncollectible Hardship (Millions of Dollars) As of March 31, 2018 As of December 31, 2017 As of March 31, 2018 As of December 31, 2017 Eversource $ 207.7 $ 195.7 $ 123.7 $ 122.5 CL&P 82.8 78.9 67.7 65.5 NSTAR Electric 72.6 69.7 38.5 40.3 PSNH 10.9 10.5 — — In accordance with new revenue accounting guidance, bad debt expense associated with customers' accounts receivable included in Operations and Maintenance expense on the statements of income is presented as follows: For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Eversource $ 19.6 $ 15.9 CL&P 3.9 2.8 NSTAR Electric 7.5 6.5 PSNH 1.7 1.7 E. Fair Value Measurements Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases" or "normal sales" ("normal") and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill and AROs, and the estimated fair value of preferred stock and long-term debt. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and Eversource's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below: Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products. Determination of Fair Value: The valuation techniques and inputs used in Eversource's fair value measurements are described in Note 4, "Derivative Instruments," Note 5, "Marketable Securities," and Note 10, "Fair Value of Financial Instruments," to the financial statements. F. Other Income, Net The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended March 31, 2018 March 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components (1) $ 15.2 $ 3.0 $ 8.4 $ 2.3 $ 8.0 $ 0.5 $ 5.0 $ 1.6 AFUDC Equity 9.7 2.8 3.4 — 6.7 2.0 1.9 — Equity in Earnings 4.6 — — — 4.6 — 0.1 — Investment Income/(Loss) 0.7 (0.1 ) 0.6 — 0.7 (0.3 ) 1.2 0.7 Interest Income 3.5 0.9 0.2 2.4 1.6 1.1 0.1 0.5 Other 0.1 — — — — — — — Total Other Income, Net (1) $ 33.8 $ 6.6 $ 12.6 $ 4.7 $ 21.6 $ 3.3 $ 8.3 $ 2.8 (1) As a result of the adoption of new accounting guidance, the non-service related components of pension, SERP and PBOP benefit costs are presented as non-operating income and recorded in Other Income, Net on the statements of income. The 2017 amounts, which were previously presented within Operations and Maintenance expense on the statements of income, have been retrospectively presented to Other Income, Net for the three months ended March 31, 2017. Eversource elected the practical expedient in the accounting guidance that allows the Company to use the amounts disclosed in its Pension Benefits and Postretirement Benefits Other Than Pension footnote for the prior period presentations as the estimation basis for applying the retrospective presentation requirements. G. Other Taxes Eversource's companies that serve customers in Connecticut collect gross receipts taxes levied by the state of Connecticut from their customers. These gross receipts taxes are shown separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Eversource $ 43.4 $ 42.2 CL&P 35.6 33.9 As agents for state and local governments, Eversource's companies that serve customers in Connecticut and Massachusetts collect certain sales taxes that are recorded on a net basis with no impact on the statements of income. Separately from the amounts above are $12.7 million of expense recorded as Taxes Other than Income Taxes in the first quarter of 2018 related to the future remittance of energy efficiency funds collected from customers in Operating Revenues to the State of Connecticut. These amounts are shown separately with collections in Operating Revenues and expenses in Taxes Other than Income Taxes on the Eversource and CL&P statements of income. H. Supplemental Cash Flow Information Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of March 31, 2018 As of March 31, 2017 Eversource $ 274.4 $ 220.5 CL&P 117.7 104.2 NSTAR Electric 59.5 49.4 PSNH 36.0 28.7 The following table reconciles cash and cash equivalents as reported on the balance sheets to the cash, cash equivalents, and restricted cash as reported on the statements of cash flows: As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Cash and Cash Equivalents as reported on the Balance Sheets $ 303.8 $ 240.2 $ 9.5 $ 2.9 $ 38.2 $ 6.0 $ 1.8 $ 0.9 Restricted cash included in: Prepayments and Other Current Assets 35.5 3.1 12.9 11.6 24.4 3.1 12.8 0.5 Marketable Securities 23.3 0.5 0.1 0.8 23.3 0.5 0.1 0.8 Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows $ 362.6 $ 243.8 $ 22.5 $ 15.3 $ 85.9 $ 9.6 $ 14.7 $ 2.2 Restricted cash included in Prepayments and Other Current Assets, shown above, primarily represents required ISO-NE cash deposits. R estricted cash included in Marketable Securities, shown above, represents money market funds held in trusts to fund certain non-qualified executive benefits and restricted trusts to fund CYAPC and YAEC's spent nuclear fuel removal obligations of their nuclear fuel storage facilities.

REGULATORY ACCOUNTING

REGULATORY ACCOUNTING	3 Months Ended
	Mar. 31, 2018
Regulated Operations [Abstract]
REGULATORY ACCOUNTING	REGULATORY ACCOUNTING Eversource's utility companies are subject to rate regulation that is based on cost recovery and meets the criteria for application of accounting guidance for rate-regulated operations, which considers the effect of regulation on the timing of the recognition of certain revenues and expenses. The regulated companies' financial statements reflect the effects of the rate-making process. The rates charged to the customers of Eversource's regulated companies are designed to collect each company's costs to provide service, including a return on investment. Management believes it is probable that each of the regulated companies will recover its respective investments in long-lived assets, including regulatory assets. If management were to determine that it could no longer apply the accounting guidance applicable to rate-regulated enterprises to any of the regulated companies' operations, or if management could not conclude it is probable that costs would be recovered from customers in future rates, the costs would be charged to net income in the period in which the determination is made. Regulatory Assets: The components of regulatory assets were as follows: Eversource As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Benefit Costs $ 2,033.5 $ 2,068.8 Income Taxes, Net 727.1 768.9 Deferred Costs from Generation Asset Sale 539.6 516.1 Storm Restoration Costs 544.4 404.8 Regulatory Tracker Mechanisms 461.1 509.9 Derivative Liabilities 388.0 367.2 Goodwill-related 361.0 365.2 Asset Retirement Obligations 88.9 101.0 Other Regulatory Assets 195.1 137.4 Total Regulatory Assets 5,338.7 5,239.3 Less: Current Portion 683.2 741.9 Total Long-Term Regulatory Assets $ 4,655.5 $ 4,497.4 As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Benefit Costs $ 460.6 $ 549.9 $ 208.6 $ 469.2 $ 560.7 $ 212.3 Income Taxes, Net 451.8 115.6 20.5 453.8 113.2 21.7 Deferred Costs from Generation Asset Sale — — 539.6 — — 516.1 Storm Restoration Costs 254.4 246.4 43.6 216.7 146.6 41.5 Regulatory Tracker Mechanisms 118.0 221.4 107.7 85.3 273.0 116.4 Derivative Liabilities 386.5 — — 362.3 — — Goodwill-related — 310.0 — — 313.6 — Asset Retirement Obligations 30.8 39.8 3.4 30.3 39.0 17.0 Other Regulatory Assets 27.2 81.2 15.3 27.6 78.4 15.8 Total Regulatory Assets 1,729.3 1,564.3 938.7 1,645.2 1,524.5 940.8 Less: Current Portion 229.7 277.0 122.5 200.3 333.9 130.1 Total Long-Term Regulatory Assets $ 1,499.6 $ 1,287.3 $ 816.2 $ 1,444.9 $ 1,190.6 $ 810.7 Regulatory Costs in Long-Term Assets: Eversource's regulated companies had $123.3 million (including $21.4 million for CL&P, $43.6 million for NSTAR Electric and $38.7 million for PSNH) and $105.8 million (including $18.2 million for CL&P, $42.7 million for NSTAR Electric and $27.2 million for PSNH) of additional regulatory costs as of March 31, 2018 and December 31, 2017 , respectively, that were included in long-term assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates. Storms: In March 2018, several significant storms caused extensive damage to our electric distribution systems and significant customer outages across all three states. A storm must meet certain criteria to qualify as a major storm with the criteria specific to each state jurisdiction and utility company. Once a storm qualifies as a major storm, all qualifying expenses incurred during storm restoration efforts are deferred and recovered from customers. Costs for storms that do not meet this criteria are not separately recoverable from customers and are expensed as incurred. These March 2018 storms resulted in deferred storm restoration costs of approximately $156 million ( $52 million for CL&P, $100 million for NSTAR Electric, and $4 million for PSNH). Management believes the storm restoration costs were prudent and meet the criteria for specific cost recovery in Connecticut, Massachusetts and New Hampshire, and that recovery from customers is probable through the applicable regulatory recovery process. Regulatory Liabilities: The components of regulatory liabilities were as follows: Eversource As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Excess ADIT due to Tax Cuts and Jobs Act $ 2,895.9 $ 2,882.0 Cost of Removal 522.8 502.1 Benefit Costs 128.0 132.3 Regulatory Tracker Mechanisms 216.8 136.7 AFUDC - Transmission 67.6 67.1 Revenue Subject to Refund (1) 26.0 — Other Regulatory Liabilities 52.6 45.2 Total Regulatory Liabilities 3,909.7 3,765.4 Less: Current Portion 206.0 128.1 Total Long-Term Regulatory Liabilities $ 3,703.7 $ 3,637.3 As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Excess ADIT due to Tax Cuts and Jobs Act $ 1,031.6 $ 1,091.1 $ 405.1 $ 1,031.6 $ 1,087.9 $ 405.1 Cost of Removal 34.4 298.5 39.0 23.2 293.8 37.9 Benefit Costs — 109.0 — — 112.6 — Regulatory Tracker Mechanisms 55.9 89.2 15.1 34.6 77.8 5.0 AFUDC - Transmission 48.5 19.1 — 48.8 18.3 — Revenue Subject to Refund (1) 12.5 3.7 3.1 — — — Other Regulatory Liabilities 20.4 8.7 2.9 12.9 3.7 2.7 Total Regulatory Liabilities 1,203.3 1,619.3 465.2 1,151.1 1,594.1 450.7 Less: Current Portion 66.9 89.2 15.6 39.0 79.6 6.3 Total Long-Term Regulatory Liabilities $ 1,136.4 $ 1,530.1 $ 449.6 $ 1,112.1 $ 1,514.5 $ 444.4 (1) The regulatory liability balance represents a reserve established to reflect the difference between the 35 percent federal corporate income tax rate included in rates charged to customers and the 21 percent federal income tax rate, effective January 1, 2018 as a result of the Tax Cuts and Jobs Act. Effective February 1, 2018, NSTAR Electric's base rates charged to customers have been adjusted to reflect the new federal income tax rate.

PROPERTY, PLANT AND EQUIPMENT A

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION The following tables summarize property, plant and equipment by asset category: Eversource As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Distribution - Electric $ 14,511.0 $ 14,410.5 Distribution - Natural Gas 3,273.2 3,244.2 Transmission - Electric 9,420.9 9,270.9 Distribution - Water 1,556.4 1,558.4 Generation and Solar (1) 36.2 36.2 Utility 28,797.7 28,520.2 Other (2) 698.4 693.7 Property, Plant and Equipment, Gross 29,496.1 29,213.9 Less: Accumulated Depreciation Utility (6,927.5 ) (6,846.9 ) Other (300.0 ) (286.9 ) Total Accumulated Depreciation (7,227.5 ) (7,133.8 ) Property, Plant and Equipment, Net 22,268.6 22,080.1 Construction Work in Progress 1,690.1 1,537.4 Total Property, Plant and Equipment, Net $ 23,958.7 $ 23,617.5 As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution $ 5,939.9 $ 6,532.5 $ 2,078.9 $ 5,888.3 $ 6,479.0 $ 2,083.4 Transmission 4,322.6 3,842.7 1,207.1 4,239.9 3,821.2 1,161.3 Generation and Solar (1) — 36.2 — — 36.2 — Property, Plant and Equipment, Gross 10,262.5 10,411.4 3,286.0 10,128.2 10,336.4 3,244.7 Less: Accumulated Depreciation (2,274.4 ) (2,599.3 ) (734.9 ) (2,239.0 ) (2,550.2 ) (751.8 ) Property, Plant and Equipment, Net 7,988.1 7,812.1 2,551.1 7,889.2 7,786.2 2,492.9 Construction Work in Progress 418.5 511.7 142.9 381.8 460.3 149.4 Total Property, Plant and Equipment, Net $ 8,406.6 $ 8,323.8 $ 2,694.0 $ 8,271.0 $ 8,246.5 $ 2,642.3 (1) On January 10, 2018, PSNH completed the sale of its thermal generation assets, pursuant to an agreement dated October 11, 2017. PSNH expects to complete the sale of its hydroelectric generation assets, pursuant to the agreement dated October 11, 2017, in the second quarter of 2018. As of March 31, 2018 and December 31, 2017, PSNH has classified its generation assets as held for sale. See Note 9, "Assets Held for Sale," for further information. (2) These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	DERIVATIVE INSTRUMENTS The electric and natural gas companies purchase and procure energy and energy-related products, which are subject to price volatility, for their customers. The costs associated with supplying energy to customers are recoverable from customers in future rates. These regulated companies manage the risks associated with the price volatility of energy and energy-related products through the use of derivative and non-derivative contracts. Many of the derivative contracts meet the definition of, and are designated as, normal and qualify for accrual accounting under the applicable accounting guidance. The costs and benefits of derivative contracts that meet the definition of normal are recognized in Operating Expenses on the statements of income, as applicable, as electricity or natural gas is delivered. Derivative contracts that are not designated as normal are recorded at fair value as current or long-term Derivative Assets or Derivative Liabilities on the balance sheets. For the electric and natural gas companies, regulatory assets or regulatory liabilities are recorded to offset the fair values of derivatives, as contract settlement amounts are recovered from, or refunded to, customers in their respective energy supply rates. The gross fair values of derivative assets and liabilities with the same counterparty are offset and reported as net Derivative Assets or Derivative Liabilities, with current and long-term portions, on the balance sheets. The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Commodity Supply and Price Risk Netting (1) Net Amount Recorded as a Derivative Current Derivative Assets: CL&P Level 3 $ 8.5 $ (6.5 ) $ 2.0 $ 9.5 $ (7.1 ) $ 2.4 Long-Term Derivative Assets: CL&P Level 3 80.2 (4.1 ) 76.1 71.9 (5.3 ) 66.6 Current Derivative Liabilities: Eversource Level 2 (1.3 ) 0.2 (1.1 ) (4.5 ) — (4.5 ) CL&P Level 3 (49.6 ) — (49.6 ) (54.4 ) — (54.4 ) Long-Term Derivative Liabilities: Eversource Level 2 (0.4 ) — (0.4 ) (0.4 ) — (0.4 ) CL&P Level 3 (415.0 ) — (415.0 ) (376.9 ) — (376.9 ) (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists. For further information on the fair value of derivative contracts, see Note 1E, "Summary of Significant Accounting Policies - Fair Value Measurements," to the financial statements. Derivative Contracts at Fair Value with Offsetting Regulatory Amounts Commodity Supply and Price Risk Management : As required by regulation, CL&P, along with UI, has capacity-related contracts with generation facilities. CL&P has a sharing agreement with UI, with 80 percent of the costs or benefits of each contract borne by or allocated to CL&P and 20 percent borne by or allocated to UI. The combined capacity of these contracts is 787 MW. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the capacity market price received in the ISO-NE capacity markets. In addition, CL&P has a contract to purchase 0.1 million MWh of energy per year through 2020. As of March 31, 2018 and December 31, 2017 , Eversource had New York Mercantile Exchange ("NYMEX") financial contracts for natural gas futures in order to reduce variability associated with the purchase price of 5.9 million and 9.5 million MMBtu of natural gas, respectively. For the three months ended March 31, 2018 and 2017 , there were losses of $36.1 million and $26.5 million , respectively, deferred as regulatory costs, which reflect the change in fair value associated with Eversource's derivative contracts. Fair Value Measurements of Derivative Instruments Derivative contracts classified as Level 2 in the fair value hierarchy relate to the financial contracts for natural gas futures. Prices are obtained from broker quotes and are based on actual market activity. The contracts are valued using NYMEX natural gas prices. Valuations of these contracts also incorporate discount rates using the yield curve approach. The fair value of derivative contracts classified as Level 3 utilizes significant unobservable inputs. The fair value is modeled using income techniques, such as discounted cash flow valuations adjusted for assumptions related to exit price. Significant observable inputs for valuations of these contracts include energy and energy-related product prices in future years for which quoted prices in an active market exist. Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements. The future power and capacity prices for periods that are not quoted in an active market or established at auction are based on available market data and are escalated based on estimates of inflation in order to address the full term of the contract. Valuations of derivative contracts using a discounted cash flow methodology include assumptions regarding the timing and likelihood of scheduled payments and also reflect non-performance risk, including credit, using the default probability approach based on the counterparty's credit rating for assets and the Company's credit rating for liabilities. Valuations incorporate estimates of premiums or discounts that would be required by a market participant to arrive at an exit price, using historical market transactions adjusted for the terms of the contract. The following is a summary of CL&P's Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of March 31, 2018 As of December 31, 2017 CL&P Range Period Covered Range Period Covered Capacity Prices $ 4.30 — 5.99 per kW-Month 2021 - 2026 $ 5.00 — 8.70 per kW-Month 2021 - 2026 Forward Reserve $ 0.95 — 1.00 per kW-Month 2018 - 2024 $ 1.00 — 2.00 per kW-Month 2018 - 2024 Exit price premiums of 3 percent through 16 percent are also applied to these contracts and reflect the uncertainty and illiquidity premiums that would be required based on the most recent market activity available for similar type contracts. Significant increases or decreases in future energy or capacity prices in isolation would decrease or increase, respectively, the fair value of the derivative liability. Any increases in risk premiums would increase the fair value of the derivative liability. Changes in these fair values are recorded as a regulatory asset or liability and do not impact net income. Valuations using significant unobservable inputs: The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. CL&P For the Three Months Ended March 31, (Millions of Dollars) 2018 2017 Derivatives, Net: Fair Value as of Beginning of Period $ (362.3 ) $ (420.5 ) Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities (36.9 ) (14.6 ) Settlements 12.7 21.6 Fair Value as of End of Period $ (386.5 ) $ (413.5 )

MARKETABLE SECURITIES

MARKETABLE SECURITIES	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
MARKETABLE SECURITIES	MARKETABLE SECURITIES Eversource maintains trusts that hold marketable securities to fund certain non-qualified executive benefits. These trusts are not subject to regulatory oversight by state or federal agencies. CYAPC and YAEC maintain legally restricted trusts, each of which holds marketable securities, to fund the spent nuclear fuel removal obligations of their nuclear fuel storage facilities. Equity Securities: In accordance with new accounting guidance, unrealized gains and losses on the equity securities held in Eversource's non-qualified executive benefit trust are recorded in Other Income, Net on the statements of income. The fair value of equity securities subject to this guidance as of March 31, 2018 and December 31, 2017 was approximately $50 million . For the three months ended March 31, 2018, there were unrealized losses of $0.7 million recorded in Other Income, Net related to these equity securities. Eversource's equity securities also include CYAPC's and YAEC's marketable securities held in nuclear decommissioning trusts, which had fair values of $ 267.3 million and $ 263.8 million as of March 31, 2018 and December 31, 2017, respectively. Unrealized gains and losses for these nuclear decommissioning trusts are subject to regulatory accounting treatment and are recorded in Marketable Securities with the corresponding offset to Other Long-Term Liabilities on the balance sheets, with no impact on the statements of income. Available-for-Sale Debt Securities: The following is a summary of the available-for-sale debt securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of March 31, 2018 As of December 31, 2017 Eversource (Millions of Dollars) Amortized Cost Pre-Tax Unrealized Gains Pre-Tax Unrealized Losses Fair Value Amortized Cost Pre-Tax Unrealized Gains Pre-Tax Unrealized Losses Fair Value Debt Securities $ 282.1 $ 0.8 $ (3.3 ) $ 279.6 $ 284.9 $ 3.2 $ (1.1 ) $ 287.0 Eversource's debt securities include CYAPC's and YAEC's marketable securities held in nuclear decommissioning trusts in the amounts of $235.7 million and $242.3 million as of March 31, 2018 and December 31, 2017 , respectively. Unrealized gains and losses on available-for-sale debt securities held in Eversource's non-qualified benefit trust are recorded in Accumulated Other Comprehensive Income. There have been no significant unrealized losses, other-than-temporary impairments or credit losses for the three months ended March 31, 2018 or 2017 . Factors considered in determining whether a credit loss exists include the duration and severity of the impairment, adverse conditions specifically affecting the issuer, and the payment history, ratings and rating changes of the security. For asset-backed debt securities, underlying collateral and expected future cash flows are also evaluated. As of March 31, 2018 , the contractual maturities of available-for-sale debt securities were as follows: Eversource (Millions of Dollars) Amortized Cost Fair Value Less than one year (1) $ 36.0 $ 35.9 One to five years 44.6 45.1 Six to ten years 63.9 63.3 Greater than ten years 137.6 135.3 Total Debt Securities $ 282.1 $ 279.6 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC nuclear decommissioning trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets. Realized Gains and Losses: Realized gains and losses are recorded in Other Income, Net for Eversource's non-qualified benefit trust and are offset in Other Long-Term Liabilities for CYAPC and YAEC. Eversource utilizes the specific identification basis method for the Eversource non-qualified benefit trust, and the average cost basis method for the CYAPC and YAEC nuclear decommissioning trusts to compute the realized gains and losses on the sale of marketable securities. Fair Value Measurements: The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of March 31, 2018 As of December 31, 2017 Level 1: Mutual Funds and Equities $ 317.3 $ 313.8 Money Market Funds 23.3 23.3 Total Level 1 $ 340.6 $ 337.1 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 68.0 $ 70.2 Corporate Debt Securities 43.7 50.9 Asset-Backed Debt Securities 20.7 21.2 Municipal Bonds 114.3 110.7 Other Fixed Income Securities 9.6 10.7 Total Level 2 $ 256.3 $ 263.7 Total Marketable Securities $ 596.9 $ 600.8 U.S. government issued debt securities are valued using market approaches that incorporate transactions for the same or similar bonds and adjustments for yields and maturity dates. Corporate debt securities are valued using a market approach, utilizing recent trades of the same or similar instruments and also incorporating yield curves, credit spreads and specific bond terms and conditions. Asset-backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset-backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates, and tranche information. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.

SHORT-TERM AND LONG-TERM DEBT

SHORT-TERM AND LONG-TERM DEBT	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
SHORT-TERM AND LONG-TERM DEBT	SHORT-TERM AND LONG-TERM DEBT Commercial Paper Programs and Credit Agreements : Eversource parent has a $1.45 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. Eversource parent, CL&P, PSNH, NSTAR Gas and Yankee Gas are also parties to a five -year $1.45 billion revolving credit facility. The revolving credit facility terminates on December 8, 2022 and serves to backstop Eversource parent's $1.45 billion commercial paper program. NSTAR Electric has a $650 million commercial paper program allowing NSTAR Electric to issue commercial paper as a form of short-term debt. NSTAR Electric is also a party to a five -year $650 million revolving credit facility. The revolving credit facility terminates on December 8, 2022 and serves to backstop NSTAR Electric's $650 million commercial paper program. There were no borrowings outstanding on either the Eversource parent or NSTAR Electric revolving credit facilities as of March 31, 2018 or December 31, 2017. Eversource's water distribution business has a $100 million revolving credit facility, which expires on August 19, 2019, and there were no amounts outstanding as of March 31, 2018 and $76.0 million outstanding as of December 31, 2017. The amount of borrowings outstanding and available under the commercial paper programs were as follows: Borrowings Outstanding as of Available Borrowing Capacity as of Weighted-Average Interest Rate as of March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 (Millions of Dollars) Eversource Parent Commercial Paper Program $ 682.3 $ 979.3 $ 767.7 $ 470.7 2.31 % 1.86 % NSTAR Electric Commercial Paper Program 367.0 234.0 283.0 416.0 1.75 % 1.55 % Amounts outstanding under the commercial paper programs and revolving credit facility are included in Notes Payable for Eversource and NSTAR Electric and are classified in current liabilities on the balance sheets as all borrowings are outstanding for no more than 364 days at one time. As a result of the Eversource parent long-term debt issuances on January 8, 2018, the net proceeds of which were used to repay short-term borrowings outstanding under its commercial paper program, $201.2 million of commercial paper borrowings under the Eversource parent commercial paper program were reclassified as Long-Term Debt as of December 31, 2017. As of March 31, 2018 , there were no intercompany loans from Eversource parent to CL&P and $271.3 million to PSNH. Intercompany loans from Eversource parent to other Eversource subsidiaries primarily included $276.3 million to Eversource Service as of March 31, 2018. As of December 31, 2017 , there were intercompany loans from Eversource parent of $69.5 million to CL&P and $262.9 million to PSNH. Intercompany loans from Eversource parent to other Eversource subsidiaries primarily included $115.9 million to Eversource Service and $198.0 million to NSTAR Gas as of December 31, 2017. These intercompany loans from Eversource parent are included in Notes Payable to Eversource Parent and are classified in current liabilities on the respective subsidiary's balance sheets. Intercompany loans from Eversource parent are eliminated in consolidation on Eversource's balance sheets. Long-Term Debt: The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issue Date Issuances/(Repayments) Maturity Date Use of Proceeds CL&P: 4.00% 2018 Series A First Mortgage Bonds March 2018 $ 500.0 2048 Repay long-term debt due to mature in 2018 and repay short-term borrowings 5.65% 2008 Series A First Mortgage Bonds (1) May 2008 (300.0 ) 2018 N/A PSNH: 6.00% 2008 Series O First Mortgage Bonds (1) May 2008 (110.0 ) 2018 N/A Eversource Parent: 2.50% Series I Senior Notes (2) January 2018 200.0 2021 Repay long-term debt due to mature in 2018 and repay short-term borrowings 3.30% Series M Senior Notes January 2018 450.0 2028 Repay long-term debt due to mature in 2018 1.60% Series G Senior Notes (3) January 2015 (150.0 ) 2018 N/A 1.45% Series E Senior Notes (1) May 2013 (300.0 ) 2018 N/A (1) Represents a repayment at maturity paid on May 1, 2018. (2) These notes are part of the same series issued by Eversource parent in March 2016. The aggregate outstanding principal amount for these notes is now $450 million . (3) Represents a repayment at maturity paid on January 15, 2018. As a result of the Eversource parent debt issuances in January 2018, $446.8 million of current portion of long-term debt related to two Eversource parent issuances maturing in 2018 and $201.2 million of commercial paper borrowings were reclassified to Long-Term Debt as of December 31, 2017.

PENSION BENEFITS AND POSTRETIRE

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION	3 Months Ended
	Mar. 31, 2018
Postemployment Benefits [Abstract]
PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION	PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION Eversource provides defined benefit retirement plans ("Pension Plans") that cover eligible employees, including, among others, employees of CL&P, NSTAR Electric and PSNH. In addition to the Pension Plans, Eversource maintains non-qualified defined benefit retirement plans ("SERP Plans"), which provide benefits in excess of Internal Revenue Code limitations to eligible participants consisting of current and retired employees. Eversource also provides defined benefit postretirement plans (the "PBOP Plans") that provide life insurance and a health reimbursement arrangement created for the purpose of reimbursing retirees and dependents for health insurance premiums and certain medical expenses to eligible employees that met certain age and service eligibility requirements. The components of net periodic benefit expense for the Pension, SERP and PBOP Plans are shown below. The service cost component of net periodic benefit expense and the intercompany allocations, less the capitalized portions, are included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit costs for pension, SERP and PBOP are included in Other Income, Net on the statements of income. Capitalized amounts relate to employees working on capital projects and are included in Property, Plant and Equipment, Net on the balance sheets. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric and PSNH does not include the intercompany allocations or the corresponding capitalized portion, as these amounts are cash settled on a short-term basis. Pension and SERP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Service Cost $ 22.7 $ 18.7 Interest Cost 48.4 46.3 Expected Return on Pension Plan Assets (98.0 ) (83.5 ) Actuarial Loss 36.0 33.6 Prior Service Cost 2.2 1.1 Total Net Periodic Benefit Expense $ 11.3 $ 16.2 Capitalized Pension Expense $ 7.5 $ 5.4 PBOP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Service Cost $ 2.7 $ 2.4 Interest Cost 7.6 7.2 Expected Return on Plan Assets (18.1 ) (15.9 ) Actuarial Loss 2.6 2.0 Prior Service Credit (5.9 ) (5.3 ) Total Net Periodic Benefit Income $ (11.1 ) $ (9.6 ) Capitalized PBOP Expense/(Income) $ 0.8 $ (4.6 ) Pension and SERP For the Three Months Ended March 31, 2018 For the Three Months Ended March 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Service Cost $ 5.7 $ 4.7 $ 2.9 $ 4.8 $ 4.1 $ 2.5 Interest Cost 10.6 10.8 5.3 10.5 10.4 5.2 Expected Return on Pension Plan Assets (20.8 ) (25.2 ) (10.9 ) (18.0 ) (22.0 ) (9.9 ) Actuarial Loss 7.4 10.5 3.3 6.9 10.1 2.8 Prior Service Cost 0.4 0.2 0.1 0.4 0.2 0.1 Total Net Periodic Benefit Expense $ 3.3 $ 1.0 $ 0.7 $ 4.6 $ 2.8 $ 0.7 Intercompany Allocations $ 1.4 $ 1.5 $ 0.5 $ 2.5 $ 2.4 $ 0.8 Capitalized Pension Expense $ 2.3 $ 2.1 $ 0.8 $ 2.5 $ 1.8 $ 0.3 PBOP For the Three Months Ended March 31, 2018 For the Three Months Ended March 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Service Cost $ 0.5 $ 0.5 $ 0.3 $ 0.5 $ 0.5 $ 0.3 Interest Cost 1.4 2.2 0.8 1.4 2.4 0.8 Expected Return on Plan Assets (2.6 ) (8.1 ) (1.5 ) (2.4 ) (7.1 ) (1.3 ) Actuarial Loss 0.3 0.7 0.2 0.2 0.9 0.1 Prior Service Cost/(Credit) 0.3 (4.3 ) 0.1 0.3 (4.3 ) 0.1 Total Net Periodic Benefit Income $ (0.1 ) $ (9.0 ) $ (0.1 ) $ — $ (7.6 ) $ — Intercompany Allocations $ (0.3 ) $ (0.3 ) $ (0.1 ) $ (0.3 ) $ (0.3 ) $ (0.1 ) Capitalized PBOP Expense/(Income) $ 0.2 $ 0.2 $ 0.1 $ (0.1 ) $ (3.8 ) $ —

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES A. Environmental Matters Eversource, CL&P, NSTAR Electric and PSNH are subject to environmental laws and regulations intended to mitigate or remove the effect of past operations and improve or maintain the quality of the environment. These laws and regulations require the removal or the remedy of the effect on the environment of the disposal or release of certain specified hazardous substances at current and former operating sites. Eversource, CL&P, NSTAR Electric and PSNH have an active environmental auditing and training program and each believes it is substantially in compliance with all enacted laws and regulations. The number of environmental sites and related reserves for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: As of March 31, 2018 As of December 31, 2017 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 58 $ 63.8 59 $ 54.9 CL&P 14 5.1 14 4.7 NSTAR Electric 15 2.8 15 2.7 PSNH 9 5.6 10 5.7 Included in the Eversource number of sites and reserve amounts above are former MGP sites that were operated several decades ago and manufactured gas from coal and other processes, which resulted in certain by-products remaining in the environment that may pose a potential risk to human health and the environment, for which Eversource may have potential liability. The reserve balances related to these former MGP sites were $57.8 million and $49.0 million as of March 31, 2018 and December 31, 2017 , respectively, and related primarily to the natural gas business segment. The increase in the reserve balance at the MGP sites in the first quarter of 2018 was primarily due to changes in cost estimates at sites under investigation for which additional remediation will be required. These reserve estimates are subjective in nature as they take into consideration several different remediation options at each specific site. The reliability and precision of these estimates can be affected by several factors, including new information concerning either the level of contamination at the site, the extent of Eversource's, CL&P's, NSTAR Electric's and PSNH's responsibility for remediation or the extent of remediation required, recently enacted laws and regulations, or changes in cost estimates due to certain economic factors. It is possible that new information or future developments could require a reassessment of the potential exposure to related environmental matters. As this information becomes available, management will continue to assess the potential exposure and adjust the reserves accordingly. B. Guarantees and Indemnifications In the normal course of business, Eversource parent provides credit assurances on behalf of its subsidiaries, including CL&P, NSTAR Electric and PSNH, in the form of guarantees. Eversource parent issued a guaranty on behalf of its subsidiary, NPT, under which, beginning at the time the Northern Pass Transmission line goes into commercial operation, Eversource parent will guarantee the financial obligations of NPT under the TSA with HQ in an amount not to exceed $25 million . Eversource parent's obligations under the guaranty expire upon the full, final and indefeasible payment of the guaranteed obligations. Eversource parent has also entered into a guaranty on behalf of NPT under which Eversource parent will guarantee NPT's obligations under a facility with a financial institution pursuant to which NPT may request letters of credit in an aggregate amount of up to approximately $14 million . Eversource parent has also guaranteed certain indemnification and other obligations as a result of the sales of former unregulated subsidiaries and the termination of an unregulated business, with maximum exposures either not specified or not material. Management does not anticipate a material impact to net income or cash flows as a result of these various guarantees and indemnifications. The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries to external parties, as of March 31, 2018 : Company Description Maximum Exposure (in millions) Expiration Dates On behalf of subsidiaries: Eversource Gas Transmission LLC Access Northeast Project Capital Contributions Guaranty (1) $ 185.0 2021 Various Surety Bonds (2) 41.2 2018 - 2019 Eversource Service and Rocky River Realty Company Lease Payments for Vehicles and Real Estate 7.3 2019 - 2024 (1) Eversource parent issued a declining balance guaranty on behalf of its subsidiary, Eversource Gas Transmission LLC, to guarantee the payment of the subsidiary's capital contributions for its investment in the Access Northeast project. The guaranty decreases as capital contributions are made. The guaranty will expire upon the earlier of the full performance of the guaranteed obligations or December 31, 2021. (2) Surety bond expiration dates reflect termination dates, the majority of which will be renewed or extended. Certain surety bonds contain credit ratings triggers that would require Eversource parent to post collateral in the event that the unsecured debt credit ratings of Eversource parent are downgraded. C. Spent Nuclear Fuel Obligations - Yankee Companies CL&P, NSTAR Electric and PSNH have plant closure and fuel storage cost obligations to the Yankee Companies, which have each completed the physical decommissioning of their respective nuclear facilities and are now engaged in the long-term storage of their spent fuel. The Yankee Companies collect these costs through wholesale, FERC-approved rates charged under power purchase agreements with several New England utilities, including CL&P, NSTAR Electric and PSNH. These companies in turn recover these costs from their customers through state regulatory commission-approved retail rates. The Yankee Companies have collected or are currently collecting amounts that management believes are adequate to recover the remaining plant closure and fuel storage cost estimates for the respective plants. Management believes CL&P and NSTAR Electric will recover their shares of these obligations from their customers. PSNH has recovered its total share of these costs from its customers. Spent Nuclear Fuel Litigation: The Yankee Companies have filed complaints against the DOE in the Court of Federal Claims seeking monetary damages resulting from the DOE's failure to provide for a permanent facility to store spent nuclear fuel pursuant to the terms of the 1983 spent fuel and high level waste disposal contracts between the Yankee Companies and the DOE. The court had previously awarded the Yankee Companies damages for Phase I, II and III of litigation resulting from the DOE's failure to meet its contractual obligations. These Phases covered damages incurred in the years 1998 through 2012, and the awarded damages have been received by the Yankee Companies with certain amounts of the damages refunded to their customers. DOE Phase IV Damages - On May 22, 2017, each of the Yankee Companies filed subsequent lawsuits against the DOE in the Court of Federal Claims seeking monetary damages totaling approximately $100 million for CYAPC, YAEC and MYAPC, resulting from the DOE's failure to begin accepting spent nuclear fuel for disposal covering the years from 2013 to 2016 (“DOE Phase IV”). No date is set for the DOE Phase IV trial. D. FERC ROE Complaints Four separate complaints have been filed at the FERC by combinations of New England state attorneys general, state regulatory commissions, consumer advocates, consumer groups, municipal parties and other parties (collectively the "Complainants"). In each of the first three complaints, the Complainants challenged the NETOs' base ROE of 11.14 percent that had been utilized since 2005 and sought an order to reduce it prospectively from the date of the final FERC order and for the separate 15 -month complaint periods. In the fourth complaint, filed April 29, 2016, the Complainants challenged the NETOs' base ROE of 10.57 percent and the maximum ROE for transmission incentive ("incentive cap") of 11.74 percent , asserting that these ROEs were unjust and unreasonable. In response to appeals of the FERC decision in the first complaint filed by the NETOs and the Complainants, the U.S. Court of Appeals for the D.C. Circuit (the "Court") issued a decision on April 14, 2017 vacating and remanding the FERC's decision. The Court found that the FERC failed to make an explicit finding that the 11.14 percent base ROE was unjust and unreasonable, as required under Section 206 of the Federal Power Act, before it set a new base ROE. The Court also found that the FERC did not provide a rational connection between the record evidence and its decision to select the midpoint of the upper half of the zone of reasonableness for the new base ROE. Hearings on the fourth complaint were held in December 2017 before the FERC Administrative Law Judge ("ALJ"). On March 27, 2018, the FERC ALJ issued an initial decision in that complaint, finding that the current base ROE of 10.57 percent , which has an incentive cap ROE of 11.74 percent , is not unjust and not unreasonable. A summary of the four separate complaints and the base ROEs pertinent to those complaints are as follows: Complaint 15-Month Time Period of Complaint (Beginning as of Complaint Filing Date) Original Base ROE Authorized by FERC at Time of Complaint Filing Date (1) Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (1) Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions) FERC ALJ Recommendation of Base ROE on Second, Third and Fourth Complaints First 10/1/2011 - 12/31/2012 11.14% 10.57% $— (2) N/A Second 12/27/2012 - 3/26/2014 11.14% N/A 39.1 (3) 9.59% Third 7/31/2014 - 10/30/2015 11.14% 10.57% — 10.90% Fourth 4/29/2016 - 7/28/2017 10.57% 10.57% — 10.57% (1) The ROE billed during the period October 1, 2011 through October 15, 2014 consisted of a base ROE of 11.14 percent and incentives up to 13.1 percent . On October 16, 2014, the FERC set the base ROE at 10.57 percent and an incentive cap at 11.74 percent for the first complaint period. This was also effective for all prospective billings to customers beginning October 16, 2014. This FERC order was vacated on April 14, 2017. (2) CL&P, NSTAR Electric and PSNH have refunded all amounts associated with the first complaint period, totaling $38.9 million (pre-tax and excluding interest) at Eversource (consisting of $22.4 million at CL&P, $13.7 million at NSTAR Electric and $2.8 million at PSNH), reflecting both the base ROE and incentive cap prescribed by the FERC order. (3) The reserve represents the difference between the billed rates during the second complaint period and a 10.57 percent base ROE and 11.74 percent incentive cap. The reserve consisted of $21.4 million for CL&P, $14.6 million for NSTAR Electric and $3.1 million for PSNH as of March 31, 2018 . On June 5, 2017, the NETOs, including Eversource, submitted a filing to the FERC to reinstate the base ROE of 11.14 percent with an associated ROE incentive cap of 13.5 percent effective June 8, 2017, as these were the last ROEs lawfully in effect for transmission billing purposes prior to the FERC order vacated by the Court on April 14, 2017. On October 6, 2017, the FERC did not accept the NETOs filing, temporarily leaving in place the ROEs ( 10.57 percent base ROE with an 11.74 percent incentive cap ROE) set in the first complaint proceeding until the FERC addresses the Court’s decision. On November 6, 2017, the NETOs submitted a request for rehearing of the FERC's October 6, 2017 Order rejecting the compliance filing. On October 5, 2017, the NETOs filed a series of motions, requesting that the FERC dismiss the four complaint proceedings. Alternatively, if the FERC does not dismiss the proceedings, the NETOs requested that the FERC consolidate all four complaint proceedings for expeditious resolution and/or stay the trial in the fourth complaint proceeding and resolve it based on the standards set in the April 14, 2017 Court decision. At this time, the Company cannot reasonably estimate a range of gain or loss for the complaint proceedings. No events in 2017 or 2018 provided a reasonable basis for a change to the reserve balance of $39.1 million (pre-tax and excluding interest) for the second complaint period, and the Company has not changed its reserve or recognized ROEs for any of the complaint periods. Eversource, CL&P, NSTAR Electric and PSNH currently record revenues at the 10.57 percent base ROE and incentive cap at 11.74 percent established in the October 16, 2014 FERC order. At this time, the Company cannot predict the timing or ultimate effect of the Court decision or future FERC action on any of the complaint periods or the estimated impacts on the financial position, results of operations or cash flows of Eversource, CL&P, NSTAR Electric or PSNH. The average impact of a 10 basis point change to the base ROE for each of the 15 -month complaint periods would affect Eversource's after-tax earnings by approximately $3 million . E. Eversource and NSTAR Electric Boston Harbor Civil Action On July 15, 2016, the United States Attorney on behalf of the United States Army Corps of Engineers filed a civil action in the United States District Court for the District of Massachusetts under provisions of the Rivers and Harbors Act of 1899 and the Clean Water Act against NSTAR Electric, Harbor Electric Energy Company, a wholly-owned subsidiary of NSTAR Electric ("HEEC"), and the Massachusetts Water Resources Authority (together with NSTAR Electric and HEEC, the "Defendants"). The action alleged that the Defendants failed to comply with certain permitting requirements related to the placement of the HEEC-owned electric distribution cable beneath Boston Harbor. The action sought an order to compel HEEC to comply with cable depth requirements in the United States Army Corps of Engineers' permit or alternatively to remove the electric distribution cable and cease unauthorized work in U.S. waterways. The action also sought civil penalties and other costs. The parties reached a settlement pursuant to which HEEC agreed to install a new 115 kV distribution cable across Boston Harbor to Deer Island, utilizing a different route, and remove portions of the existing cable. Upon the installation and completion of the new cable and the removal of the portions of the existing cable, all issues surrounding the current permit from the United States Army Corps of Engineers are expected to be resolved, and such litigation is expected to be dismissed with prejudice. In 2017, as a result of the settlement, NSTAR Electric expensed $4.9 million (pre-tax) of previously incurred capitalized costs associated with engineering work performed on the existing cable that will no longer be used. In addition, NSTAR Electric agreed to provide a rate base credit of $17.5 million to the Massachusetts Water Resources Authority for the new cable. This negotiated credit will result in the initial $17.5 million of construction costs on the new cable to be expensed as incurred. Of this amount, NSTAR Electric expensed $11.1 million (pre-tax) of costs incurred on the new cable in 2017 and expensed an additional $2.1 million (pre-tax) in the first three months of 2018. Construction of the new cable is underway and is expected to be completed in 2019.

ASSETS HELD FOR SALE

ASSETS HELD FOR SALE	3 Months Ended
	Mar. 31, 2018
Regulated Operations [Abstract]
ASSETS HELD FOR SALE	ASSETS HELD FOR SALE In June 2015, Eversource and PSNH entered into the 2015 Public Service Company of New Hampshire Restructuring and Rate Stabilization Agreement, under the terms of which PSNH agreed to divest its generation assets, subject to NHPUC approval. The NHPUC approval for this agreement, as well as NHPUC approval of the final divestiture plan and auction process, were received in the second half of 2016. In October 2017, PSNH entered into two Purchase and Sale Agreements ("Agreements") to sell its thermal and hydroelectric generation assets to private investors at purchase prices of $175 million and $83 million , respectively, subject to adjustments as set forth in the Agreements. The NHPUC approved the Agreements in late November 2017, at which time the Company classified these assets as held for sale. On January 10, 2018, PSNH completed the sale of its thermal generation assets, pursuant to the Agreement dated October 11, 2017. In accordance with the Purchase and Sale Agreement, the original purchase price of $175 million was adjusted to reflect working capital adjustments, closing date adjustments and proration of taxes and fees prior to closing, totaling $40.9 million , resulting in net proceeds of $134.1 million . As of March 31, 2018 , deferred costs resulting from the thermal generation asset sale totaled $539.6 million and were included in Regulatory Assets on the Eversource and PSNH Balance Sheets. As of December 31, 2017, this balance totaled $516.1 million and represented the difference between the carrying value and the fair value less cost to sell of the thermal generation assets. PSNH expects to complete the sale of its hydroelectric generation assets in the second quarter of 2018 at an amount above net carrying value, and are therefore stated at carrying value. As of March 31, 2018, the difference between the carrying value of the hydroelectric generation assets and the anticipated sale proceeds was approximately $23 million , which will be recognized as a reduction to stranded costs upon completion of the sale. Full recovery of the costs of PSNH's generation assets and transaction-related expenses is expected to occur through a combination of cash flows during the remaining operating period, sales proceeds, and recovery of stranded costs primarily via the issuance of bonds that will be secured by a non-bypassable charge billed to PSNH's customers. For the three months ended March 31, 2018 , pre-tax income associated with the hydroelectric assets held for sale was $5.9 million . For the three months ended March 31, 2017, pre-tax income associated with PSNH's generation assets was $14.8 million . As of March 31, 2018 , PSNH's hydroelectric generation assets held for sale, which are included in current assets on the Eversource and PSNH balance sheets, and are part of the Electric Distribution reportable segment, were as follows: (Millions of Dollars) Hydroelectric Gross Plant $ 86.6 Accumulated Depreciation (27.4 ) Net Plant 59.2 Materials and Supplies 0.1 Total Hydroelectric Generation Assets Held for Sale $ 59.3

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS The following methods and assumptions were used to estimate the fair value of each of the following financial instruments: Preferred Stock and Long-Term Debt: The fair value of CL&P's and NSTAR Electric's preferred stock is based upon pricing models that incorporate interest rates and other market factors, valuations or trades of similar securities and cash flow projections. The fair value of long-term debt securities is based upon pricing models that incorporate quoted market prices for those issues or similar issues adjusted for market conditions, credit ratings of the respective companies and treasury benchmark yields. The fair values provided in the tables below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows: As of March 31, 2018 As of December 31, 2017 Eversource (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 165.8 $ 155.6 $ 160.8 Long-Term Debt 13,113.3 13,376.1 12,325.5 12,877.1 CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of March 31, 2018: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 122.3 $ 43.0 $ 43.5 $ — $ — Long-Term Debt 3,553.6 3,821.9 2,943.9 3,071.7 1,001.8 1,025.2 As of December 31, 2017: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 116.5 $ 43.0 $ 44.3 $ — $ — Long-Term Debt 3,059.1 3,430.5 2,943.8 3,156.5 1,002.4 1,038.2 Derivative Instruments and Marketable Securities: Derivative instruments and investments in marketable securities are carried at fair value. For further information, see Note 4, "Derivative Instruments," and Note 5, "Marketable Securities," to the financial statements. See Note 1E, "Summary of Significant Accounting Policies - Fair Value Measurements," for the fair value measurement policy and the fair value hierarchy.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) The changes in accumulated other comprehensive income/(loss) by component, net of tax, is as follows: For the Three Months Ended March 31, 2018 For the Three Months Ended March 31, 2017 Eversource (Millions of Dollars) Qualified Cash Flow Hedging Instruments Unrealized Losses on Marketable Securities Defined Benefit Plans Total Qualified Cash Flow Hedging Instruments Unrealized Gains on Marketable Securities Defined Benefit Plans Total Balance as of Beginning of Period $ (6.2 ) $ — $ (60.2 ) $ (66.4 ) $ (8.2 ) $ 0.4 $ (57.5 ) $ (65.3 ) OCI Before Reclassifications — (0.4 ) — (0.4 ) — 1.7 — 1.7 Amounts Reclassified from AOCI 0.7 — 3.0 3.7 0.5 — 1.0 1.5 Net OCI 0.7 (0.4 ) 3.0 3.3 0.5 1.7 1.0 3.2 Balance as of End of Period $ (5.5 ) $ (0.4 ) $ (57.2 ) $ (63.1 ) $ (7.7 ) $ 2.1 $ (56.5 ) $ (62.1 ) Eversource's qualified cash flow hedging instruments represent interest rate swap agreements on debt issuances that were settled in prior years. The settlement amount was recorded in AOCI and is being amortized into Net Income over the term of the underlying debt instrument. CL&P, NSTAR Electric and PSNH continue to amortize interest rate swaps settled in prior years from AOCI into Interest Expense over the remaining life of the associated long-term debt. Such interest rate swaps are not material to their respective financial statements. Defined benefit plan OCI amounts before reclassifications relate to actuarial gains and losses and prior service costs that arose during the year and were recognized in AOCI. The unamortized actuarial gains and losses and prior service costs on the defined benefit plans are amortized from AOCI into Other Income, Net over the average future employee service period, and are reflected in amounts reclassified from AOCI. For further information, see Note 1F, "Summary of Significant Accounting Policies - Other Income, Net," and Note 7, "Pension Benefits and Postretirement Benefits Other Than Pension."

COMMON SHARES

COMMON SHARES	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
COMMON SHARES	COMMON SHARES The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Authorized as of March 31, 2018 and Issued as of Par Value December 31, 2017 March 31, 2018 December 31, 2017 Eversource $ 5 380,000,000 333,878,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 As of both March 31, 2018 and December 31, 2017 , there were 16,992,594 Eversource common shares held as treasury shares. As of both March 31, 2018 and December 31, 2017 , there were 316,885,808 Eversource common shares outstanding. COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS Dividends on the preferred stock of CL&P and NSTAR Electric totaled $1.9 million for each of the three months ended March 31, 2018 and 2017 . These dividends were presented as Net Income Attributable to Noncontrolling Interests on the Eversource statements of income. Noncontrolling Interest – Preferred Stock of Subsidiaries on the Eversource balance sheets totaled $155.6 million as of March 31, 2018 and December 31, 2017 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to the parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest.

COMMON SHAREHOLDERS' EQUITY AND

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	COMMON SHARES The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Authorized as of March 31, 2018 and Issued as of Par Value December 31, 2017 March 31, 2018 December 31, 2017 Eversource $ 5 380,000,000 333,878,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 As of both March 31, 2018 and December 31, 2017 , there were 16,992,594 Eversource common shares held as treasury shares. As of both March 31, 2018 and December 31, 2017 , there were 316,885,808 Eversource common shares outstanding. COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS Dividends on the preferred stock of CL&P and NSTAR Electric totaled $1.9 million for each of the three months ended March 31, 2018 and 2017 . These dividends were presented as Net Income Attributable to Noncontrolling Interests on the Eversource statements of income. Noncontrolling Interest – Preferred Stock of Subsidiaries on the Eversource balance sheets totaled $155.6 million as of March 31, 2018 and December 31, 2017 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to the parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest.

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic EPS is computed based upon the weighted average number of common shares outstanding during each period. Diluted EPS is computed on the basis of the weighted average number of common shares outstanding plus the potential dilutive effect of certain share-based compensation awards as if they were converted into common shares. The dilutive effect of unvested RSU and performance share awards is calculated using the treasury stock method. RSU and performance share awards are included in basic weighted average common shares outstanding as of the date that all necessary vesting conditions have been satisfied. For the three months ended March 31, 2018 and 2017 , there were no antidilutive share awards excluded from the computation of diluted EPS. The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended March 31, 2018 March 31, 2017 Net Income Attributable to Common Shareholders $ 269.5 $ 259.5 Weighted Average Common Shares Outstanding: Basic 317,397,052 317,463,151 Dilutive Effect 595,947 661,385 Diluted 317,992,999 318,124,536 Basic and Diluted EPS $ 0.85 $ 0.82

REVENUES

REVENUES	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES On January 1, 2018, Eversource, including CL&P, NSTAR Electric and PSNH, adopted ASU 2014-09, “ Revenue from Contracts with Customers (Topic 606) ” using the modified retrospective approach. The core principle of this accounting guidance is that revenue is recognized when promised goods or services (referred to as performance obligations) are transferred to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new standard uses a five-step model for recognizing and measuring revenue from contracts with customers, which includes identifying the contract with the customer, identifying the performance obligations promised within the contract, determining the transaction price (the amount of consideration to which the company expects to be entitled), allocating the transaction price to the performance obligations and recognizing revenue when (or as) the performance obligation is satisfied. The following table presents operating revenues disaggregated by revenue source: For the Three Months Ended March 31, 2018 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenue from Contracts with Customers Retail Tariff Sales Residential $ 994.4 $ 248.9 $ — $ 26.4 $ — $ — $ 1,269.7 Commercial 611.4 134.7 — 13.8 — — 759.9 Industrial 81.5 29.5 — 1.0 — (2.5 ) 109.5 Total Retail Tariff Sales Revenue $ 1,687.3 $ 413.1 $ — $ 41.2 $ — $ (2.5 ) $ 2,139.1 Wholesale Transmission Revenue $ — $ — $ 313.6 $ — $ 10.1 $ (258.7 ) $ 65.0 Wholesale Market Sales Revenue 58.5 17.8 — 0.8 — — 77.1 Other Revenue from Contracts with Customers 16.0 (0.6 ) 3.1 4.0 220.8 (221.4 ) 21.9 Reserve for Revenue Subject to Refund (19.3 ) (4.5 ) — (2.2 ) — — (26.0 ) Total Revenue from Contracts with Customers $ 1,742.5 $ 425.8 $ 316.7 $ 43.8 $ 230.9 $ (482.6 ) $ 2,277.1 Alternative Revenue Programs 8.7 (1.7 ) (11.7 ) 0.7 — 10.6 6.6 Other Revenue 3.4 0.8 — 0.1 — — 4.3 Total Operating Revenues $ 1,754.6 $ 424.9 $ 305.0 $ 44.6 $ 230.9 $ (472.0 ) $ 2,288.0 For the Three Months Ended March 31, 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH Revenue from Contracts with Customers Retail Tariff Sales Residential $ 483.4 $ 364.2 $ 146.8 Commercial 222.5 314.4 74.9 Industrial 35.8 28.1 17.6 Total Retail Tariff Sales Revenue $ 741.7 $ 706.7 $ 239.3 Wholesale Transmission Revenue $ 150.8 $ 118.6 $ 44.2 Wholesale Market Sales Revenue 10.3 24.9 24.1 Other Revenue from Contracts with Customers 7.5 8.3 3.5 Reserve for Revenue Subject to Refund (12.5 ) (3.7 ) (3.1 ) Total Revenue from Contracts with Customers $ 897.8 $ 854.8 $ 308.0 Alternative Revenue Programs (5.1 ) 6.7 (4.6 ) Other Revenue 1.3 1.7 0.4 Eliminations (109.0 ) (93.1 ) (36.4 ) Total Operating Revenues $ 785.0 $ 770.1 $ 267.4 Retail Tariff Sales: Regulated utilities provide products and services to their regulated customers under rates, pricing, payment terms and conditions of service, regulated by each state regulatory agency. The arrangement whereby a utility provides commodity service to a customer for a price approved by the respective state regulatory commission is referred to as a tariff sale contract, and the tariff governs all aspects of the provision of regulated services by utilities. The majority of revenue for Eversource, CL&P, NSTAR Electric and PSNH is derived from regulated retail tariff sales for the sale and distribution of electricity, natural gas and water to residential, commercial and industrial retail customers. The utility's performance obligation for the regulated tariff sales is to provide electricity, natural gas or water to the customer as demanded. The promise to provide the commodity represents a single performance obligation, as it is a promise to transfer a series of distinct goods or services that are substantially the same and that have the same pattern of transfer to the customer . Revenue is recognized over time as the customer simultaneously receives and consumes the benefits provided by the utility, and the utility satisfies its performance obligation. Revenue is recognized based on the output method as there is a directly observable output to the customer (electricity, natural gas or water units delivered to the customer and immediately consumed). Each Eversource utility is entitled to be compensated for performance completed to date (service taken by the customer) until service is terminated. In regulated tariff sales, the transaction prices are the rates approved by the respective state regulatory commissions. In general, rates can only be changed through formal proceedings with the state regulatory commissions. These rates are designed to recover the costs to provide service to customers and include a return on investment. Regulatory commission-approved tracking mechanisms are included in these rates and are also used to recover, on a fully-reconciling basis, certain costs, such as the procurement of energy supply, retail transmission charges, energy efficiency program costs, net metering for distributed generation, and restructuring and stranded costs. These tracking mechanisms result in rates being changed periodically to ensure recovery of actual costs incurred. Customers may elect to purchase electricity from each Eversource electric utility or may contract separately with a competitive third party supplier. Revenue is not recorded for the sale of the electricity commodity to customers who have contracted separately with these suppliers, only the delivery to a customer, as the utility is acting as an agent on behalf of the third party supplier. Wholesale Transmission Revenues: The Eversource electric transmission-owning companies (CL&P, NSTAR Electric and PSNH) each own and maintain transmission facilities that are part of an interstate power transmission grid over which electricity is transmitted throughout New England. CL&P, NSTAR Electric and PSNH, as well as most other New England utilities, are parties to a series of agreements that provide for coordinated planning and operation of the region's transmission facilities and the rules by which they acquire transmission services. The Eversource electric transmission-owning companies have a combination of FERC-approved regional and local formula rates that work in tandem to recover all their transmission costs. These rates are part of the ISO-NE Tariff. Regional rates recover the costs of higher voltage transmission facilities that benefit the region and are collected from all New England transmission customers, including the Eversource distribution businesses. Eversource's local rates recover the companies' total transmission revenue requirements, less revenues received from regional rates and other sources, and are collected from Eversource's distribution businesses and other transmission customers. The distribution businesses of Eversource, in turn, recover the FERC approved charges from retail customers through annual or semiannual tracking mechanisms, which are retail tariff sales. The utility's performance obligation for regulated wholesale transmission sales is to provide transmission services to the customer as demanded. The promise to provide transmission service represents a single performance obligation. The transaction prices are the transmission rate formulas as defined by the ISO-NE Tariff and are regulated and established by FERC. Wholesale transmission revenue is recognized over time as the performance obligation is completed, which occurs as transmission services are provided to customers. The revenue is recognized based on the output method. Each Eversource utility is entitled to be compensated for performance completed to date (e.g., use of the transmission system by the customer). Wholesale Market Sales Revenues: Wholesale market sales transactions include sales of energy and energy-related products into the ISO-NE wholesale electricity market, sales of natural gas to third party marketers, and also the sale of RECs to various counterparties. ISO-NE oversees the region's wholesale electricity market and administers the transactions and terms and conditions, including payment terms, which are established in the ISO-NE tariff, between the buyers and sellers in the market. Pricing is set by the wholesale market. The wholesale transactions in the ISO-NE market occur on a day-ahead basis or a real-time basis (daily) and are, therefore, short-term. Transactions are tracked and reported by ISO-NE net by the hour, which is the net hourly position of energy sales and purchases by each market participant. Beginning in the first quarter of 2018, the performance obligation for ISO-NE energy transactions is defined to be the net by hour transaction. Revenue is recognized when the performance obligation for these energy sales transactions is satisfied, when the sale occurs and the energy is transferred to the customer. For sales of natural gas, transportation, and natural gas pipeline capacity to third party marketers, revenue is recognized when the performance obligation is satisfied at the point in time the sale occurs and the natural gas or related product is transferred to the marketer. RECs are sold to various counterparties, and revenue is recognized when the performance obligation is satisfied upon transfer of title to the customer through the New England Power Pool Generation Information System. Other Revenue from Contracts with Customers: Other revenue from contracts with customers primarily includes property rentals that are not deemed leases. These revenues are generally recognized on a straight-line basis over time as the service is provided to the customer. Reserve for Revenue Subject to Refund: Current base rates include an estimate of income taxes, which was based on the U.S. federal corporate income tax rate in effect at the time of the rate proceeding. In the first quarter of 2018, Eversource established a reserve of $26.0 million , recorded as a reduction to revenue, to reflect the difference between the 35 percent federal corporate income tax rate included in rates charged to customers and the 21 percent federal income tax rate, effective January 1, 2018 as a result of the Tax Cuts and Jobs Act. Eversource will refund these amounts to customers through various rate mechanisms in the future. Effective February 1, 2018, NSTAR Electric's base rates charged to customers have been adjusted to reflect the new federal income tax rate, and effective May 1, 2018, CL&P's rates charged to customers reflect the new income tax rate. Alternative Revenue Programs: In accordance with accounting guidance for rate-regulated operations, certain of Eversource's utilities' rate making mechanisms qualify as alternative revenue programs ("ARPs") if they meet specified criteria, in which case revenues may be recognized prior to billing based on allowed levels of collection in rates. Eversource's utility companies recognize revenue and record a regulatory asset or liability once the condition or event allowing for the automatic adjustment of future rates occurs. ARP revenues include both the recognition of the deferral adjustment to ARP revenues, when the regulator-specified condition or event allowing for additional billing or refund has occurred, and an equal and offsetting reversal of the ARP deferral to revenues as those amounts are reflected in the price of service in subsequent periods. Eversource’s ARPs include the revenue decoupling mechanism and annual reconciliation adjustment to transmission formula rates, described below. • Certain Eversource electric, natural gas and water companies, including CL&P and NSTAR Electric, have revenue decoupling mechanism approved by a regulatory commission ("decoupled companies"). Decoupled companies’ distribution revenues are not directly based on sales volumes. The decoupled companies reconcile their annual base distribution rate recovery to pre-established levels of baseline distribution delivery service revenues, with any difference between the allowed level of distribution revenue and the actual amount realized adjusted through subsequent rates. • The transmission formula rates provide for the annual reconciliation and recovery or refund of estimated costs to actual costs. The financial impacts of differences between actual and estimated costs are deferred for future recovery from, or refund to, transmission customers. This transmission deferral reconciles billed transmission revenues to the revenue requirement for our transmission businesses. Other Revenues: Other Revenues include certain fees charged to customers and lease revenue that are not considered revenue from contracts with customers. Intercompany Eliminations: Intercompany eliminations are primarily related to the Eversource electric transmission revenues that are derived from ISO-NE regional transmission charges to the distribution businesses of CL&P, NSTAR Electric and PSNH that recover the costs of the wholesale transmission business and revenues from Eversource's service company. Intercompany revenues and expenses between the Eversource wholesale transmission businesses and the Eversource distribution businesses and from Eversource's service company are eliminated in consolidation and included in "Eliminations" in the table above. Receivables: Receivables, Net on the balance sheet include trade receivables from our retail customers and receivables arising from ISO-NE billing related to wholesale transmission contracts and wholesale market transactions, sales of natural gas and capacity to marketers, sales of RECs, and property rentals. In general, retail tariff customers and wholesale transmission customers are billed monthly and the payment terms are generally due and payable upon receipt of the bill. Unbilled Revenues on the balance sheet represent estimated amounts due from retail customers for electricity, natural gas or water delivered to customers but not yet billed. The utility company has satisfied its performance obligation and the customer has received and consumed the commodity as of the balance sheet date, and therefore, the utility company records revenue for those services in the period the services were provided. Only the passage of time is required before the company is entitled to payment for the satisfaction of the performance obligation. Payment from customers is due monthly as services are rendered and amounts are billed. Actual amounts billed to customers when meter readings become available may vary from the estimated amount. Unbilled revenues are recognized by allocating estimated unbilled sales volumes to the respective customer classes, and then applying an estimated rate by customer class to those sales volumes. Unbilled revenue estimates reflect seasonality, weather, customer usage patterns, customer rates in effect for customer classes, and the timing of customer billing. The companies that have a decoupling mechanism record a regulatory deferral to reflect the actual allowed amount of revenue associated with their respective decoupled distribution rate design. Practical Expedients: Eversource has elected practical expedients in the accounting guidance that allow the company to record revenue in the amount that the company has a right to invoice, if that amount corresponds directly with the value to the customer of the company's performance to date, and not to disclose related unsatisfied performance obligations. Retail and wholesale transmission tariff sales fall into this category, as these sales are recognized as revenue in the period the utility provides the service and completes the performance obligation, which is the same as the monthly amount billed to customers. There are no other material revenue streams for which Eversource has unsatisfied performance obligations.

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Presentation: Eversource is organized among the Electric Distribution, Electric Transmission, Natural Gas Distribution and Water Distribution reportable segments and Other based on a combination of factors, including the characteristics of each segments' services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates. These reportable segments represent substantially all of Eversource's total consolidated revenues. Revenues from the sale of electricity, natural gas and water primarily are derived from residential, commercial and industrial customers and are not dependent on any single customer. The Electric Distribution reportable segment includes the results of PSNH's generation facilities and NSTAR Electric's solar power facilities. Eversource's reportable segments are determined based upon the level at which Eversource's chief operating decision maker assesses performance and makes decisions about the allocation of company resources. On December 4, 2017, Eversource acquired Aquarion, which was considered to be a new operating segment, water distribution. Though the water distribution segment does not meet quantitative thresholds under the segment reporting accounting guidance, based on qualitative factors including the nature of the water distribution business, Water Distribution was deemed a reportable segment beginning in the first quarter of 2018. The remainder of Eversource's operations is presented as Other in the tables below and primarily consists of 1) the equity in earnings of Eversource parent from its subsidiaries and intercompany interest income, both of which are eliminated in consolidation, and interest expense related to the debt of Eversource parent, 2) the revenues and expenses of Eversource Service, most of which are eliminated in consolidation, 3) the operations of CYAPC and YAEC, and 4) the results of other unregulated subsidiaries, which are not part of its core business. In addition, Other in the tables below includes Eversource parent's equity ownership interests in certain natural gas pipeline projects owned by Enbridge, Inc., the Bay State Wind project, a renewable energy investment fund, and two companies that transmit hydroelectricity imported from the Hydro-Quebec system in Canada. In the ordinary course of business, Yankee Gas and NSTAR Gas purchase natural gas transmission services from the Enbridge, Inc. natural gas pipeline projects described above. These affiliate transaction costs total approximately $62.5 million annually and are classified as Purchased Power, Fuel and Transmission on the Eversource statements of income. Each of Eversource's subsidiaries, including CL&P, NSTAR Electric and PSNH, has one reportable segment. Cash flows used for investments in plant included in the segment information below are cash capital expenditures that do not include amounts incurred but not paid, cost of removal, AFUDC related to equity funds, and the capitalized portions of pension expense. Eversource's segment information is as follows: For the Three Months Ended March 31, 2018 (1) Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,754.6 $ 424.9 $ 305.0 $ 44.6 $ 230.9 $ (472.0 ) $ 2,288.0 Depreciation and Amortization (144.4 ) (26.4 ) (56.6 ) (10.7 ) (12.0 ) 0.6 (249.5 ) Other Operating Expenses (1,443.5 ) (312.6 ) (83.2 ) (23.9 ) (204.7 ) 471.9 (1,596.0 ) Operating Income $ 166.7 $ 85.9 $ 165.2 $ 10.0 $ 14.2 $ 0.5 $ 442.5 Interest Expense $ (47.4 ) $ (11.1 ) $ (29.7 ) $ (8.4 ) $ (31.9 ) $ 7.4 $ (121.1 ) Other Income, Net 19.6 2.0 8.0 (0.6 ) 360.1 (355.3 ) 33.8 Net Income Attributable to Common Shareholders 104.2 57.8 107.4 1.5 346.0 (347.4 ) 269.5 Cash Flows Used for Investments in Plant 236.0 70.4 239.2 19.0 42.7 — 607.3 For the Three Months Ended March 31, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,401.1 $ 403.6 $ 316.9 $ — $ 236.3 $ (252.8 ) $ 2,105.1 Depreciation and Amortization (129.8 ) (21.7 ) (50.6 ) — (9.2 ) 0.5 (210.8 ) Other Operating Expenses (1,048.9 ) (290.2 ) (90.2 ) — (216.8 ) 252.8 (1,393.3 ) Operating Income $ 222.4 $ 91.7 $ 176.1 $ — $ 10.3 $ 0.5 $ 501.0 Interest Expense $ (48.2 ) $ (10.6 ) $ (28.1 ) $ — $ (19.7 ) $ 3.2 $ (103.4 ) Other Income, Net 12.0 0.9 5.1 — 329.1 (325.5 ) 21.6 Net Income Attributable to Common Shareholders 114.1 50.8 94.2 — 322.2 (321.8 ) 259.5 Cash Flows Used for Investments in Plant 236.2 64.5 192.6 — 30.3 — 523.6 (1) Effective January 1, 2018, upon implementation of the new revenue accounting guidance, the electric distribution segment is presented gross and intercompany transmission billings are presented in the eliminations column, as Eversource believes that the electric distribution segment acts as a principal, rather than an agent, in its contracts with retail customers. Retail customers contract directly with the electric distribution utility and do not differentiate between distribution and transmission services. Therefore, the electric distribution segment revenues, which are derived from retail customer billings, are presented gross of the eliminations. Prior to 2018, the electric distribution segment presented intercompany electric transmission billings net, based on indicators of net presentation prior to the new revenue guidance. See Note 15, "Revenues," regarding accounting for revenues. The following table summarizes Eversource's segmented total assets: Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Water Distribution Other Eliminations Total As of March 31, 2018 $ 21,167.9 $ 3,636.8 $ 9,833.2 $ 2,487.9 $ 16,586.5 $ (16,672.3 ) $ 37,040.0 As of December 31, 2017 19,250.4 3,595.2 9,401.2 2,470.0 15,933.8 (14,430.2 ) 36,220.4

ACQUISITION OF AQUARION

ACQUISITION OF AQUARION	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
ACQUISITION OF AQUARION	ACQUISITION OF AQUARION On December 4, 2017, Eversource acquired Aquarion from Macquarie Infrastructure Partners for $1.675 billion , a purchase price consisting of approximately $880 million in cash and $795 million of assumed Aquarion debt. Aquarion is a holding company primarily engaged, through its three separate regulated water utility subsidiaries, in the water collection, treatment and distribution business, and operates in Connecticut, Massachusetts and New Hampshire. These regulated utilities collect, treat and distribute water to residential, commercial and industrial customers, to other utilities for resale, and for private and municipal fire protection. Aquarion and its subsidiaries became wholly-owned subsidiaries of Eversource, and Eversource's consolidated financial information includes Aquarion and its subsidiaries' activity beginning December 4, 2017. The approximate $880 million cash purchase price included the $745 million equity purchase price and a $135 million shareholder loan, paid at closing. Purchase Price Allocation : The purchase price allocation reflects a measurement period adjustment recorded as of March 31, 2018 to revise the fair value of Aquarion's regulated debt. The $7.9 million increase to the fair value of Long-Term Debt and corresponding increase to Regulatory Assets, included within Other Noncurrent Assets, excluding Goodwill in the table below, will be amortized over the life of the related debt. The preliminary allocation of the cash purchase price is as follows: (Millions of Dollars) Current Assets $ 41.2 PP&E 1,034.9 Goodwill 907.9 Other Noncurrent Assets, excluding Goodwill 215.5 Current Liabilities (121.9 ) Noncurrent Liabilities (421.6 ) Long-Term Debt (778.3 ) Total Cash Purchase Price $ 877.7

SUMMARY OF SIGNIFICANT ACCOUN23

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Accounting Standards	Accounting Standards Accounting Standards Issued but Not Yet Effective: In February 2016, the FASB issued Accounting Standards Update ("ASU") 2016-02, Leases , which changes existing lease accounting guidance and is required to be applied in the first quarter of 2019, with earlier application permitted. The ASU lease criteria are required to be applied to leases and lease renewals entered into effective January 1, 2019. The Company will implement the ASU in the first quarter of 2019. The requirements of the ASU include balance sheet recognition of leases previously deemed to be operating leases, and additional disclosure requirements. The Company is in the process of evaluating what impact the ASU will have on its financial statements. As of December 31, 2017, Eversource’s total future undiscounted minimum rental payments, excluding executory costs, under long-term noncancelable operating and capital leases were less than $100 million . Accounting Standards Recently Adopted: On January 1, 2018, Eversource, CL&P, NSTAR Electric and PSNH adopted ASU 2014-09, Revenue from Contracts with Customers , which amended existing revenue recognition guidance, using the modified retrospective method (cumulatively at the date of initial application) applying it only to contracts that were not complete at January 1, 2018. Under this method of adoption, prior year reported results were not restated. Implementation of the ASU did not have a material effect on the results of operations, financial position or cash flows of Eversource, CL&P, NSTAR Electric or PSNH. See Note 15, "Revenues," for further information . The Company identified an item that was accounted for differently under the new revenue guidance, as compared to the previously existing guidance. As a result of applying guidance on the unit of account under the new standard, purchases of power from and sales of power to ISO-New England are now accounted for net by the hour, rather than net by the month. This change increased Operating Revenues and Purchased Power, Fuel and Transmission by $19 million for the three months ended March 31, 2018, with no impact on net income. On January 1, 2018, Eversource adopted ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Liabilities . The ASU removed the available-for-sale designation for equity securities, whereby changes in fair value were previously recorded in accumulated other comprehensive income within shareholders' equity, and required changes in fair value of all equity securities to be recorded in earnings effective January 1, 2018. There was no cumulative effect of adoption. For the three months ended March 31, 2018, unrealized losses recorded in Other Income, Net were $0.7 million . For further information, see Note 5, "Marketable Securities," to the financial statements. On January 1, 2018, Eversource, CL&P, NSTAR Electric and PSNH adopted ASU 2017-07, Compensation – Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The ASU required separate presentation of service cost from other components of net pension and PBOP costs, with the other components presented as non-operating income and not subject to capitalization. The ASU has been applied retrospectively for the separate presentation in the income statement of service costs and other components and prospectively in the balance sheet for the capitalization of only the service cost component. As of March 31, 2018, the non-service cost components of net pension, SERP and PBOP costs that were not capitalized in plant were recorded as an increase to regulatory liabilities of approximately $10 million , as these amounts continue to be included in rates. See Note 1F, "Summary of Significant Accounting Policies - Other Income, Net," to the financial statements for the portion of pension and PBOP costs that are presented as non-operating income for the three months ended March 31, 2018 and 2017. The March 31, 2017 amounts, which were previously presented within Operations and Maintenance expense on the statements of income, totaled $8.0 million at Eversource, $0.5 million at CL&P, $5.0 million at NSTAR Electric and $1.6 million at PSNH, and have been retrospectively presented to Other Income, Net. On January 1, 2018, Eversource, CL&P, NSTAR Electric and PSNH adopted two accounting standards relating to the statement of cash flows; ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments, and ASU 2016-18, Restricted Cash. As a result of implementing ASU 2016-15, dividends from equity method investments of $6.2 million and $4.8 million in the first quarter of 2018 and 2017, respectively, are presented in operating activities at Eversource, for which the 2017 amounts were previously classified in investing activities. ASU 2016-18 required that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash and restricted cash equivalents. Both standards were applied retrospectively, as required, and neither had a material impact on Eversource's, CL&P's, NSTAR Electric's or PSNH's statements of cash flows. See Note 1H, "Summary of Significant Accounting Policies - Supplemental Cash Flow Information," to the financial statements for a reconciliation of cash and cash equivalents as reported on the balance sheet to the statement of cash flows, which includes amounts described as restricted cash and restricted cash equivalents. C. Northern Pass Northern Pass is Eversource's planned 1,090 MW HVDC transmission line that will interconnect from the Québec-New Hampshire border to Franklin, New Hampshire and an associated alternating current radial transmission line between Franklin and Deerfield, New Hampshire. As of March 31, 2018, our capitalized Northern Pass project costs were approximately $289 million . In March 2018, the Massachusetts EDCs terminated contract negotiations with and conditional selection of Northern Pass under the Massachusetts Clean Energy RFP, and the New Hampshire Site Evaluation Committee ("NHSEC") issued a written decision denying Northern Pass’ siting application. NPT reviewed the written decision and filed a motion for rehearing with the NHSEC on April 27, 2018. The NHSEC denial of Northern Pass' siting application caused us to review the recoverability of our Northern Pass project costs. In this recoverability review, we estimated undiscounted expected project cash flows and compared the result to our estimated project costs to determine whether the recorded amount is recoverable. Our undiscounted cash flows were substantially in excess of our estimated project costs. We completed this analysis and concluded that our project costs are recoverable based on our expectation that the Northern Pass project remains probable of being placed in service. Consistent with Eversource’s and HQ’s long-term relationship to bring clean energy into New England, Eversource and HQ remain committed to Northern Pass and the many benefits this project will bring to our customers and the region. If as a result of future events and changes in circumstances a new recoverability review were to conclude that our project costs are not recoverable, then we would reduce Northern Pass' project costs to the estimated fair value, which could result in most of our $289 million of capitalized project costs being written off. Such a write off could have a material adverse effect on our financial position and results of operations.
Provision for Uncollectible Accounts	Provision for Uncollectible Accounts Eversource, including CL&P, NSTAR Electric and PSNH, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectability from customers. Management continuously assesses the collectability of receivables and adjusts collectability estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the customer accounts are terminated and these balances are deemed to be uncollectible. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric and NSTAR Gas to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. These uncollectible hardship customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets.
Fair Value Measurements	Fair Value Measurements Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases" or "normal sales" ("normal") and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill and AROs, and the estimated fair value of preferred stock and long-term debt. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and Eversource's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below: Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products.
Other Taxes	Other Taxes Eversource's companies that serve customers in Connecticut collect gross receipts taxes levied by the state of Connecticut from their customers. As agents for state and local governments, Eversource's companies that serve customers in Connecticut and Massachusetts collect certain sales taxes that are recorded on a net basis with no impact on the statements of income.

SUMMARY OF SIGNIFICANT ACCOUN24

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	The total provision for both uncollectible accounts and for uncollectible hardship accounts (the uncollectible hardship balance is included in the total provision) is included in Receivables, Net on the balance sheets, and is as follows: Total Provision for Uncollectible Accounts Uncollectible Hardship (Millions of Dollars) As of March 31, 2018 As of December 31, 2017 As of March 31, 2018 As of December 31, 2017 Eversource $ 207.7 $ 195.7 $ 123.7 $ 122.5 CL&P 82.8 78.9 67.7 65.5 NSTAR Electric 72.6 69.7 38.5 40.3 PSNH 10.9 10.5 — — In accordance with new revenue accounting guidance, bad debt expense associated with customers' accounts receivable included in Operations and Maintenance expense on the statements of income is presented as follows: For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Eversource $ 19.6 $ 15.9 CL&P 3.9 2.8 NSTAR Electric 7.5 6.5 PSNH 1.7 1.7
Schedule of Other Income, Net	The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended March 31, 2018 March 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components (1) $ 15.2 $ 3.0 $ 8.4 $ 2.3 $ 8.0 $ 0.5 $ 5.0 $ 1.6 AFUDC Equity 9.7 2.8 3.4 — 6.7 2.0 1.9 — Equity in Earnings 4.6 — — — 4.6 — 0.1 — Investment Income/(Loss) 0.7 (0.1 ) 0.6 — 0.7 (0.3 ) 1.2 0.7 Interest Income 3.5 0.9 0.2 2.4 1.6 1.1 0.1 0.5 Other 0.1 — — — — — — — Total Other Income, Net (1) $ 33.8 $ 6.6 $ 12.6 $ 4.7 $ 21.6 $ 3.3 $ 8.3 $ 2.8 (1) As a result of the adoption of new accounting guidance, the non-service related components of pension, SERP and PBOP benefit costs are presented as non-operating income and recorded in Other Income, Net on the statements of income. The 2017 amounts, which were previously presented within Operations and Maintenance expense on the statements of income, have been retrospectively presented to Other Income, Net for the three months ended March 31, 2017. Eversource elected the practical expedient in the accounting guidance that allows the Company to use the amounts disclosed in its Pension Benefits and Postretirement Benefits Other Than Pension footnote for the prior period presentations as the estimation basis for applying the retrospective presentation requirements.
State Of Connecticut Gross Earnings Taxes	These gross receipts taxes are shown separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Eversource $ 43.4 $ 42.2 CL&P 35.6 33.9
Schedule of Supplemental Cash Flow Information	Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of March 31, 2018 As of March 31, 2017 Eversource $ 274.4 $ 220.5 CL&P 117.7 104.2 NSTAR Electric 59.5 49.4 PSNH 36.0 28.7
Schedule of Cash and Cash Equivalents	The following table reconciles cash and cash equivalents as reported on the balance sheets to the cash, cash equivalents, and restricted cash as reported on the statements of cash flows: As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Cash and Cash Equivalents as reported on the Balance Sheets $ 303.8 $ 240.2 $ 9.5 $ 2.9 $ 38.2 $ 6.0 $ 1.8 $ 0.9 Restricted cash included in: Prepayments and Other Current Assets 35.5 3.1 12.9 11.6 24.4 3.1 12.8 0.5 Marketable Securities 23.3 0.5 0.1 0.8 23.3 0.5 0.1 0.8 Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows $ 362.6 $ 243.8 $ 22.5 $ 15.3 $ 85.9 $ 9.6 $ 14.7 $ 2.2

REGULATORY ACCOUNTING (Tables)

REGULATORY ACCOUNTING (Tables)	3 Months Ended
	Mar. 31, 2018
Regulated Operations [Abstract]
Schedule of Regulatory Assets	The components of regulatory assets were as follows: Eversource As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Benefit Costs $ 2,033.5 $ 2,068.8 Income Taxes, Net 727.1 768.9 Deferred Costs from Generation Asset Sale 539.6 516.1 Storm Restoration Costs 544.4 404.8 Regulatory Tracker Mechanisms 461.1 509.9 Derivative Liabilities 388.0 367.2 Goodwill-related 361.0 365.2 Asset Retirement Obligations 88.9 101.0 Other Regulatory Assets 195.1 137.4 Total Regulatory Assets 5,338.7 5,239.3 Less: Current Portion 683.2 741.9 Total Long-Term Regulatory Assets $ 4,655.5 $ 4,497.4 As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Benefit Costs $ 460.6 $ 549.9 $ 208.6 $ 469.2 $ 560.7 $ 212.3 Income Taxes, Net 451.8 115.6 20.5 453.8 113.2 21.7 Deferred Costs from Generation Asset Sale — — 539.6 — — 516.1 Storm Restoration Costs 254.4 246.4 43.6 216.7 146.6 41.5 Regulatory Tracker Mechanisms 118.0 221.4 107.7 85.3 273.0 116.4 Derivative Liabilities 386.5 — — 362.3 — — Goodwill-related — 310.0 — — 313.6 — Asset Retirement Obligations 30.8 39.8 3.4 30.3 39.0 17.0 Other Regulatory Assets 27.2 81.2 15.3 27.6 78.4 15.8 Total Regulatory Assets 1,729.3 1,564.3 938.7 1,645.2 1,524.5 940.8 Less: Current Portion 229.7 277.0 122.5 200.3 333.9 130.1 Total Long-Term Regulatory Assets $ 1,499.6 $ 1,287.3 $ 816.2 $ 1,444.9 $ 1,190.6 $ 810.7
Schedule of Regulatory Liabilities	The components of regulatory liabilities were as follows: Eversource As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Excess ADIT due to Tax Cuts and Jobs Act $ 2,895.9 $ 2,882.0 Cost of Removal 522.8 502.1 Benefit Costs 128.0 132.3 Regulatory Tracker Mechanisms 216.8 136.7 AFUDC - Transmission 67.6 67.1 Revenue Subject to Refund (1) 26.0 — Other Regulatory Liabilities 52.6 45.2 Total Regulatory Liabilities 3,909.7 3,765.4 Less: Current Portion 206.0 128.1 Total Long-Term Regulatory Liabilities $ 3,703.7 $ 3,637.3 As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Excess ADIT due to Tax Cuts and Jobs Act $ 1,031.6 $ 1,091.1 $ 405.1 $ 1,031.6 $ 1,087.9 $ 405.1 Cost of Removal 34.4 298.5 39.0 23.2 293.8 37.9 Benefit Costs — 109.0 — — 112.6 — Regulatory Tracker Mechanisms 55.9 89.2 15.1 34.6 77.8 5.0 AFUDC - Transmission 48.5 19.1 — 48.8 18.3 — Revenue Subject to Refund (1) 12.5 3.7 3.1 — — — Other Regulatory Liabilities 20.4 8.7 2.9 12.9 3.7 2.7 Total Regulatory Liabilities 1,203.3 1,619.3 465.2 1,151.1 1,594.1 450.7 Less: Current Portion 66.9 89.2 15.6 39.0 79.6 6.3 Total Long-Term Regulatory Liabilities $ 1,136.4 $ 1,530.1 $ 449.6 $ 1,112.1 $ 1,514.5 $ 444.4 (1) The regulatory liability balance represents a reserve established to reflect the difference between the 35 percent federal corporate income tax rate included in rates charged to customers and the 21 percent federal income tax rate, effective January 1, 2018 as a result of the Tax Cuts and Jobs Act. Effective February 1, 2018, NSTAR Electric's base rates charged to customers have been adjusted to reflect the new federal income tax rate.

PROPERTY, PLANT AND EQUIPMENT26

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Public Utility Property, Plant, and Equipment	The following tables summarize property, plant and equipment by asset category: Eversource As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Distribution - Electric $ 14,511.0 $ 14,410.5 Distribution - Natural Gas 3,273.2 3,244.2 Transmission - Electric 9,420.9 9,270.9 Distribution - Water 1,556.4 1,558.4 Generation and Solar (1) 36.2 36.2 Utility 28,797.7 28,520.2 Other (2) 698.4 693.7 Property, Plant and Equipment, Gross 29,496.1 29,213.9 Less: Accumulated Depreciation Utility (6,927.5 ) (6,846.9 ) Other (300.0 ) (286.9 ) Total Accumulated Depreciation (7,227.5 ) (7,133.8 ) Property, Plant and Equipment, Net 22,268.6 22,080.1 Construction Work in Progress 1,690.1 1,537.4 Total Property, Plant and Equipment, Net $ 23,958.7 $ 23,617.5 As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution $ 5,939.9 $ 6,532.5 $ 2,078.9 $ 5,888.3 $ 6,479.0 $ 2,083.4 Transmission 4,322.6 3,842.7 1,207.1 4,239.9 3,821.2 1,161.3 Generation and Solar (1) — 36.2 — — 36.2 — Property, Plant and Equipment, Gross 10,262.5 10,411.4 3,286.0 10,128.2 10,336.4 3,244.7 Less: Accumulated Depreciation (2,274.4 ) (2,599.3 ) (734.9 ) (2,239.0 ) (2,550.2 ) (751.8 ) Property, Plant and Equipment, Net 7,988.1 7,812.1 2,551.1 7,889.2 7,786.2 2,492.9 Construction Work in Progress 418.5 511.7 142.9 381.8 460.3 149.4 Total Property, Plant and Equipment, Net $ 8,406.6 $ 8,323.8 $ 2,694.0 $ 8,271.0 $ 8,246.5 $ 2,642.3 (1) On January 10, 2018, PSNH completed the sale of its thermal generation assets, pursuant to an agreement dated October 11, 2017. PSNH expects to complete the sale of its hydroelectric generation assets, pursuant to the agreement dated October 11, 2017, in the second quarter of 2018. As of March 31, 2018 and December 31, 2017, PSNH has classified its generation assets as held for sale. See Note 9, "Assets Held for Sale," for further information. (2) These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service.

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of March 31, 2018 As of December 31, 2017 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Commodity Supply and Price Risk Netting (1) Net Amount Recorded as a Derivative Current Derivative Assets: CL&P Level 3 $ 8.5 $ (6.5 ) $ 2.0 $ 9.5 $ (7.1 ) $ 2.4 Long-Term Derivative Assets: CL&P Level 3 80.2 (4.1 ) 76.1 71.9 (5.3 ) 66.6 Current Derivative Liabilities: Eversource Level 2 (1.3 ) 0.2 (1.1 ) (4.5 ) — (4.5 ) CL&P Level 3 (49.6 ) — (49.6 ) (54.4 ) — (54.4 ) Long-Term Derivative Liabilities: Eversource Level 2 (0.4 ) — (0.4 ) (0.4 ) — (0.4 ) CL&P Level 3 (415.0 ) — (415.0 ) (376.9 ) — (376.9 ) (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists.
Fair Value Inputs, Liabilities, Quantitative Information	The following is a summary of CL&P's Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of March 31, 2018 As of December 31, 2017 CL&P Range Period Covered Range Period Covered Capacity Prices $ 4.30 — 5.99 per kW-Month 2021 - 2026 $ 5.00 — 8.70 per kW-Month 2021 - 2026 Forward Reserve $ 0.95 — 1.00 per kW-Month 2018 - 2024 $ 1.00 — 2.00 per kW-Month 2018 - 2024
Rollforward Of Net Derivative Asset Liabilities Valued Using Unobservable Inputs	The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. CL&P For the Three Months Ended March 31, (Millions of Dollars) 2018 2017 Derivatives, Net: Fair Value as of Beginning of Period $ (362.3 ) $ (420.5 ) Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities (36.9 ) (14.6 ) Settlements 12.7 21.6 Fair Value as of End of Period $ (386.5 ) $ (413.5 )

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities Reconciliation	The following is a summary of the available-for-sale debt securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of March 31, 2018 As of December 31, 2017 Eversource (Millions of Dollars) Amortized Cost Pre-Tax Unrealized Gains Pre-Tax Unrealized Losses Fair Value Amortized Cost Pre-Tax Unrealized Gains Pre-Tax Unrealized Losses Fair Value Debt Securities $ 282.1 $ 0.8 $ (3.3 ) $ 279.6 $ 284.9 $ 3.2 $ (1.1 ) $ 287.0
Investments Classified by Contractual Maturity Date	As of March 31, 2018 , the contractual maturities of available-for-sale debt securities were as follows: Eversource (Millions of Dollars) Amortized Cost Fair Value Less than one year (1) $ 36.0 $ 35.9 One to five years 44.6 45.1 Six to ten years 63.9 63.3 Greater than ten years 137.6 135.3 Total Debt Securities $ 282.1 $ 279.6 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC nuclear decommissioning trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets.
Fair Value on a Recurring Basis	The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of March 31, 2018 As of December 31, 2017 Level 1: Mutual Funds and Equities $ 317.3 $ 313.8 Money Market Funds 23.3 23.3 Total Level 1 $ 340.6 $ 337.1 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 68.0 $ 70.2 Corporate Debt Securities 43.7 50.9 Asset-Backed Debt Securities 20.7 21.2 Municipal Bonds 114.3 110.7 Other Fixed Income Securities 9.6 10.7 Total Level 2 $ 256.3 $ 263.7 Total Marketable Securities $ 596.9 $ 600.8

SHORT-TERM AND LONG-TERM DEBT (

SHORT-TERM AND LONG-TERM DEBT (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issue Date Issuances/(Repayments) Maturity Date Use of Proceeds CL&P: 4.00% 2018 Series A First Mortgage Bonds March 2018 $ 500.0 2048 Repay long-term debt due to mature in 2018 and repay short-term borrowings 5.65% 2008 Series A First Mortgage Bonds (1) May 2008 (300.0 ) 2018 N/A PSNH: 6.00% 2008 Series O First Mortgage Bonds (1) May 2008 (110.0 ) 2018 N/A Eversource Parent: 2.50% Series I Senior Notes (2) January 2018 200.0 2021 Repay long-term debt due to mature in 2018 and repay short-term borrowings 3.30% Series M Senior Notes January 2018 450.0 2028 Repay long-term debt due to mature in 2018 1.60% Series G Senior Notes (3) January 2015 (150.0 ) 2018 N/A 1.45% Series E Senior Notes (1) May 2013 (300.0 ) 2018 N/A (1) Represents a repayment at maturity paid on May 1, 2018. (2) These notes are part of the same series issued by Eversource parent in March 2016. The aggregate outstanding principal amount for these notes is now $450 million . (3) Represents a repayment at maturity paid on January 15, 2018.

PENSION BENEFITS AND POSTRETI30

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION (Tables)	3 Months Ended
	Mar. 31, 2018
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit expense for the Pension, SERP and PBOP Plans are shown below. The service cost component of net periodic benefit expense and the intercompany allocations, less the capitalized portions, are included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit costs for pension, SERP and PBOP are included in Other Income, Net on the statements of income. Capitalized amounts relate to employees working on capital projects and are included in Property, Plant and Equipment, Net on the balance sheets. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric and PSNH does not include the intercompany allocations or the corresponding capitalized portion, as these amounts are cash settled on a short-term basis. Pension and SERP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Service Cost $ 22.7 $ 18.7 Interest Cost 48.4 46.3 Expected Return on Pension Plan Assets (98.0 ) (83.5 ) Actuarial Loss 36.0 33.6 Prior Service Cost 2.2 1.1 Total Net Periodic Benefit Expense $ 11.3 $ 16.2 Capitalized Pension Expense $ 7.5 $ 5.4 PBOP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2018 March 31, 2017 Service Cost $ 2.7 $ 2.4 Interest Cost 7.6 7.2 Expected Return on Plan Assets (18.1 ) (15.9 ) Actuarial Loss 2.6 2.0 Prior Service Credit (5.9 ) (5.3 ) Total Net Periodic Benefit Income $ (11.1 ) $ (9.6 ) Capitalized PBOP Expense/(Income) $ 0.8 $ (4.6 ) Pension and SERP For the Three Months Ended March 31, 2018 For the Three Months Ended March 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Service Cost $ 5.7 $ 4.7 $ 2.9 $ 4.8 $ 4.1 $ 2.5 Interest Cost 10.6 10.8 5.3 10.5 10.4 5.2 Expected Return on Pension Plan Assets (20.8 ) (25.2 ) (10.9 ) (18.0 ) (22.0 ) (9.9 ) Actuarial Loss 7.4 10.5 3.3 6.9 10.1 2.8 Prior Service Cost 0.4 0.2 0.1 0.4 0.2 0.1 Total Net Periodic Benefit Expense $ 3.3 $ 1.0 $ 0.7 $ 4.6 $ 2.8 $ 0.7 Intercompany Allocations $ 1.4 $ 1.5 $ 0.5 $ 2.5 $ 2.4 $ 0.8 Capitalized Pension Expense $ 2.3 $ 2.1 $ 0.8 $ 2.5 $ 1.8 $ 0.3 PBOP For the Three Months Ended March 31, 2018 For the Three Months Ended March 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Service Cost $ 0.5 $ 0.5 $ 0.3 $ 0.5 $ 0.5 $ 0.3 Interest Cost 1.4 2.2 0.8 1.4 2.4 0.8 Expected Return on Plan Assets (2.6 ) (8.1 ) (1.5 ) (2.4 ) (7.1 ) (1.3 ) Actuarial Loss 0.3 0.7 0.2 0.2 0.9 0.1 Prior Service Cost/(Credit) 0.3 (4.3 ) 0.1 0.3 (4.3 ) 0.1 Total Net Periodic Benefit Income $ (0.1 ) $ (9.0 ) $ (0.1 ) $ — $ (7.6 ) $ — Intercompany Allocations $ (0.3 ) $ (0.3 ) $ (0.1 ) $ (0.3 ) $ (0.3 ) $ (0.1 ) Capitalized PBOP Expense/(Income) $ 0.2 $ 0.2 $ 0.1 $ (0.1 ) $ (3.8 ) $ —

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Environmental Loss Contingencies by Site	The number of environmental sites and related reserves for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: As of March 31, 2018 As of December 31, 2017 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 58 $ 63.8 59 $ 54.9 CL&P 14 5.1 14 4.7 NSTAR Electric 15 2.8 15 2.7 PSNH 9 5.6 10 5.7
Schedule of Guarantor Obligations	The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries to external parties, as of March 31, 2018 : Company Description Maximum Exposure (in millions) Expiration Dates On behalf of subsidiaries: Eversource Gas Transmission LLC Access Northeast Project Capital Contributions Guaranty (1) $ 185.0 2021 Various Surety Bonds (2) 41.2 2018 - 2019 Eversource Service and Rocky River Realty Company Lease Payments for Vehicles and Real Estate 7.3 2019 - 2024 (1) Eversource parent issued a declining balance guaranty on behalf of its subsidiary, Eversource Gas Transmission LLC, to guarantee the payment of the subsidiary's capital contributions for its investment in the Access Northeast project. The guaranty decreases as capital contributions are made. The guaranty will expire upon the earlier of the full performance of the guaranteed obligations or December 31, 2021. (2) Surety bond expiration dates reflect termination dates, the majority of which will be renewed or extended. Certain surety bonds contain credit ratings triggers that would require Eversource parent to post collateral in the event that the unsecured debt credit ratings of Eversource parent are downgraded.
Schedule of Complaints and Base ROE	A summary of the four separate complaints and the base ROEs pertinent to those complaints are as follows: Complaint 15-Month Time Period of Complaint (Beginning as of Complaint Filing Date) Original Base ROE Authorized by FERC at Time of Complaint Filing Date (1) Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (1) Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions) FERC ALJ Recommendation of Base ROE on Second, Third and Fourth Complaints First 10/1/2011 - 12/31/2012 11.14% 10.57% $— (2) N/A Second 12/27/2012 - 3/26/2014 11.14% N/A 39.1 (3) 9.59% Third 7/31/2014 - 10/30/2015 11.14% 10.57% — 10.90% Fourth 4/29/2016 - 7/28/2017 10.57% 10.57% — 10.57% (1) The ROE billed during the period October 1, 2011 through October 15, 2014 consisted of a base ROE of 11.14 percent and incentives up to 13.1 percent . On October 16, 2014, the FERC set the base ROE at 10.57 percent and an incentive cap at 11.74 percent for the first complaint period. This was also effective for all prospective billings to customers beginning October 16, 2014. This FERC order was vacated on April 14, 2017. (2) CL&P, NSTAR Electric and PSNH have refunded all amounts associated with the first complaint period, totaling $38.9 million (pre-tax and excluding interest) at Eversource (consisting of $22.4 million at CL&P, $13.7 million at NSTAR Electric and $2.8 million at PSNH), reflecting both the base ROE and incentive cap prescribed by the FERC order. (3) The reserve represents the difference between the billed rates during the second complaint period and a 10.57 percent base ROE and 11.74 percent incentive cap. The reserve consisted of $21.4 million for CL&P, $14.6 million for NSTAR Electric and $3.1 million for PSNH as of March 31, 2018 .

ASSETS HELD FOR SALE (Tables)

ASSETS HELD FOR SALE (Tables)	3 Months Ended
	Mar. 31, 2018
Regulated Operations [Abstract]
Schedule of Generation Assets and Liabilities	As of March 31, 2018 , PSNH's hydroelectric generation assets held for sale, which are included in current assets on the Eversource and PSNH balance sheets, and are part of the Electric Distribution reportable segment, were as follows: (Millions of Dollars) Hydroelectric Gross Plant $ 86.6 Accumulated Depreciation (27.4 ) Net Plant 59.2 Materials and Supplies 0.1 Total Hydroelectric Generation Assets Held for Sale $ 59.3

FAIR VALUE OF FINANCIAL INSTR33

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	Carrying amounts and estimated fair values are as follows: As of March 31, 2018 As of December 31, 2017 Eversource (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 165.8 $ 155.6 $ 160.8 Long-Term Debt 13,113.3 13,376.1 12,325.5 12,877.1 CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of March 31, 2018: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 122.3 $ 43.0 $ 43.5 $ — $ — Long-Term Debt 3,553.6 3,821.9 2,943.9 3,071.7 1,001.8 1,025.2 As of December 31, 2017: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 116.5 $ 43.0 $ 44.3 $ — $ — Long-Term Debt 3,059.1 3,430.5 2,943.8 3,156.5 1,002.4 1,038.2

ACCUMULATED OTHER COMPREHENSI34

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The changes in accumulated other comprehensive income/(loss) by component, net of tax, is as follows: For the Three Months Ended March 31, 2018 For the Three Months Ended March 31, 2017 Eversource (Millions of Dollars) Qualified Cash Flow Hedging Instruments Unrealized Losses on Marketable Securities Defined Benefit Plans Total Qualified Cash Flow Hedging Instruments Unrealized Gains on Marketable Securities Defined Benefit Plans Total Balance as of Beginning of Period $ (6.2 ) $ — $ (60.2 ) $ (66.4 ) $ (8.2 ) $ 0.4 $ (57.5 ) $ (65.3 ) OCI Before Reclassifications — (0.4 ) — (0.4 ) — 1.7 — 1.7 Amounts Reclassified from AOCI 0.7 — 3.0 3.7 0.5 — 1.0 1.5 Net OCI 0.7 (0.4 ) 3.0 3.3 0.5 1.7 1.0 3.2 Balance as of End of Period $ (5.5 ) $ (0.4 ) $ (57.2 ) $ (63.1 ) $ (7.7 ) $ 2.1 $ (56.5 ) $ (62.1 )

COMMON SHARES (Tables)

COMMON SHARES (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Stock by Class	The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Authorized as of March 31, 2018 and Issued as of Par Value December 31, 2017 March 31, 2018 December 31, 2017 Eversource $ 5 380,000,000 333,878,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended March 31, 2018 March 31, 2017 Net Income Attributable to Common Shareholders $ 269.5 $ 259.5 Weighted Average Common Shares Outstanding: Basic 317,397,052 317,463,151 Dilutive Effect 595,947 661,385 Diluted 317,992,999 318,124,536 Basic and Diluted EPS $ 0.85 $ 0.82

REVENUES (Tables)

REVENUES (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following table presents operating revenues disaggregated by revenue source: For the Three Months Ended March 31, 2018 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenue from Contracts with Customers Retail Tariff Sales Residential $ 994.4 $ 248.9 $ — $ 26.4 $ — $ — $ 1,269.7 Commercial 611.4 134.7 — 13.8 — — 759.9 Industrial 81.5 29.5 — 1.0 — (2.5 ) 109.5 Total Retail Tariff Sales Revenue $ 1,687.3 $ 413.1 $ — $ 41.2 $ — $ (2.5 ) $ 2,139.1 Wholesale Transmission Revenue $ — $ — $ 313.6 $ — $ 10.1 $ (258.7 ) $ 65.0 Wholesale Market Sales Revenue 58.5 17.8 — 0.8 — — 77.1 Other Revenue from Contracts with Customers 16.0 (0.6 ) 3.1 4.0 220.8 (221.4 ) 21.9 Reserve for Revenue Subject to Refund (19.3 ) (4.5 ) — (2.2 ) — — (26.0 ) Total Revenue from Contracts with Customers $ 1,742.5 $ 425.8 $ 316.7 $ 43.8 $ 230.9 $ (482.6 ) $ 2,277.1 Alternative Revenue Programs 8.7 (1.7 ) (11.7 ) 0.7 — 10.6 6.6 Other Revenue 3.4 0.8 — 0.1 — — 4.3 Total Operating Revenues $ 1,754.6 $ 424.9 $ 305.0 $ 44.6 $ 230.9 $ (472.0 ) $ 2,288.0 For the Three Months Ended March 31, 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH Revenue from Contracts with Customers Retail Tariff Sales Residential $ 483.4 $ 364.2 $ 146.8 Commercial 222.5 314.4 74.9 Industrial 35.8 28.1 17.6 Total Retail Tariff Sales Revenue $ 741.7 $ 706.7 $ 239.3 Wholesale Transmission Revenue $ 150.8 $ 118.6 $ 44.2 Wholesale Market Sales Revenue 10.3 24.9 24.1 Other Revenue from Contracts with Customers 7.5 8.3 3.5 Reserve for Revenue Subject to Refund (12.5 ) (3.7 ) (3.1 ) Total Revenue from Contracts with Customers $ 897.8 $ 854.8 $ 308.0 Alternative Revenue Programs (5.1 ) 6.7 (4.6 ) Other Revenue 1.3 1.7 0.4 Eliminations (109.0 ) (93.1 ) (36.4 ) Total Operating Revenues $ 785.0 $ 770.1 $ 267.4

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Eversource's segment information is as follows: For the Three Months Ended March 31, 2018 (1) Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,754.6 $ 424.9 $ 305.0 $ 44.6 $ 230.9 $ (472.0 ) $ 2,288.0 Depreciation and Amortization (144.4 ) (26.4 ) (56.6 ) (10.7 ) (12.0 ) 0.6 (249.5 ) Other Operating Expenses (1,443.5 ) (312.6 ) (83.2 ) (23.9 ) (204.7 ) 471.9 (1,596.0 ) Operating Income $ 166.7 $ 85.9 $ 165.2 $ 10.0 $ 14.2 $ 0.5 $ 442.5 Interest Expense $ (47.4 ) $ (11.1 ) $ (29.7 ) $ (8.4 ) $ (31.9 ) $ 7.4 $ (121.1 ) Other Income, Net 19.6 2.0 8.0 (0.6 ) 360.1 (355.3 ) 33.8 Net Income Attributable to Common Shareholders 104.2 57.8 107.4 1.5 346.0 (347.4 ) 269.5 Cash Flows Used for Investments in Plant 236.0 70.4 239.2 19.0 42.7 — 607.3 For the Three Months Ended March 31, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,401.1 $ 403.6 $ 316.9 $ — $ 236.3 $ (252.8 ) $ 2,105.1 Depreciation and Amortization (129.8 ) (21.7 ) (50.6 ) — (9.2 ) 0.5 (210.8 ) Other Operating Expenses (1,048.9 ) (290.2 ) (90.2 ) — (216.8 ) 252.8 (1,393.3 ) Operating Income $ 222.4 $ 91.7 $ 176.1 $ — $ 10.3 $ 0.5 $ 501.0 Interest Expense $ (48.2 ) $ (10.6 ) $ (28.1 ) $ — $ (19.7 ) $ 3.2 $ (103.4 ) Other Income, Net 12.0 0.9 5.1 — 329.1 (325.5 ) 21.6 Net Income Attributable to Common Shareholders 114.1 50.8 94.2 — 322.2 (321.8 ) 259.5 Cash Flows Used for Investments in Plant 236.2 64.5 192.6 — 30.3 — 523.6 (1) Effective January 1, 2018, upon implementation of the new revenue accounting guidance, the electric distribution segment is presented gross and intercompany transmission billings are presented in the eliminations column, as Eversource believes that the electric distribution segment acts as a principal, rather than an agent, in its contracts with retail customers. Retail customers contract directly with the electric distribution utility and do not differentiate between distribution and transmission services. Therefore, the electric distribution segment revenues, which are derived from retail customer billings, are presented gross of the eliminations. Prior to 2018, the electric distribution segment presented intercompany electric transmission billings net, based on indicators of net presentation prior to the new revenue guidance. See Note 15, "Revenues," regarding accounting for revenues. The following table summarizes Eversource's segmented total assets: Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Water Distribution Other Eliminations Total As of March 31, 2018 $ 21,167.9 $ 3,636.8 $ 9,833.2 $ 2,487.9 $ 16,586.5 $ (16,672.3 ) $ 37,040.0 As of December 31, 2017 19,250.4 3,595.2 9,401.2 2,470.0 15,933.8 (14,430.2 ) 36,220.4

ACQUISITION OF AQUARION (Tables

ACQUISITION OF AQUARION (Tables)	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Schedule of Business Acquisition by Acquisition	The preliminary allocation of the cash purchase price is as follows: (Millions of Dollars) Current Assets $ 41.2 PP&E 1,034.9 Goodwill 907.9 Other Noncurrent Assets, excluding Goodwill 215.5 Current Liabilities (121.9 ) Noncurrent Liabilities (421.6 ) Long-Term Debt (778.3 ) Total Cash Purchase Price $ 877.7

SUMMARY OF SIGNIFICANT ACCOUN40

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Basis of Presentation (Details) $ in Thousands, customer in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)MW	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)customerutility
Schedule of Equity Method Investments [Line Items]
Undiscounted minimum rental payments, excluding executory costs, under long-term noncancelable operating and capital leases			$ 100,000
increase in operating revenues and purchased power, fuel and transmission	$ 19,000
Number of electric and natural gas customers | customer			4
Increase in regulatory liabilities	10,000
Other Income, Net	$ 33,789	$ 21,619
Capacity required for transmission line | MW	1,090
Amount capitalized in transmission line installation	$ 289,000
Connecticut, Massachusetts and New Hampshire
Schedule of Equity Method Investments [Line Items]
Number of regulated utilities | utility			8
Accounting Standards Update 2016-01
Schedule of Equity Method Investments [Line Items]
Unrealized losses recorded in other income	700
Accounting Standards Update 2016-15
Schedule of Equity Method Investments [Line Items]
New guidance on equity method investments	$ 6,200	$ 4,800

SUMMARY OF SIGNIFICANT ACCOUN41

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts Narrative (Details)	3 Months Ended
	Mar. 31, 2018
Maximum | The Connecticut Light And Power Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of accounts receivable recoverable under financial or medical duress	180 days
Minimum | Yankee Gas Services Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of accounts receivable recoverable under financial or medical duress	90 days

SUMMARY OF SIGNIFICANT ACCOUN42

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	$ 207.7	$ 195.7
Uncollectible Hardship	123.7	122.5
Bad debt expense associated with accounts receivable	19.6		$ 15.9
The Connecticut Light And Power Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	82.8	78.9
Uncollectible Hardship	67.7	65.5
Bad debt expense associated with accounts receivable	3.9		2.8
NSTAR Electric Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	72.6	69.7
Uncollectible Hardship	38.5	40.3
Bad debt expense associated with accounts receivable	7.5		6.5
Public Service Company Of New Hampshire
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	10.9	10.5
Uncollectible Hardship	0	$ 0
Bad debt expense associated with accounts receivable	$ 1.7		$ 1.7

SUMMARY OF SIGNIFICANT ACCOUN43

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Income, Net Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Income, Net [Line Items]
Other Income, Net	$ 33,789	$ 21,619
Total Other Income, Net
Other Income, Net [Line Items]
Other Income, Net	$ 33,800	$ 21,600

SUMMARY OF SIGNIFICANT ACCOUN44

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Summary of Accounting Policies [Line Items]
Other Income, Net	$ 33,789	$ 21,619
Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	15,200	8,000
AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	9,700	6,700
Equity in Earnings
Summary of Accounting Policies [Line Items]
Other Income, Net	4,600	4,600
Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net	700	700
Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	3,500	1,600
Other
Summary of Accounting Policies [Line Items]
Other Income, Net	100	0
Total Other Income, Net
Summary of Accounting Policies [Line Items]
Other Income, Net	33,800	21,600
The Connecticut Light And Power Company
Summary of Accounting Policies [Line Items]
Other Income, Net	6,560	3,267
The Connecticut Light And Power Company | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	3,000	500
The Connecticut Light And Power Company | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	2,800	2,000
The Connecticut Light And Power Company | Equity in Earnings
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0
The Connecticut Light And Power Company | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net	(100)	(300)
The Connecticut Light And Power Company | Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	900	1,100
The Connecticut Light And Power Company | Other
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0
The Connecticut Light And Power Company | Total Other Income, Net
Summary of Accounting Policies [Line Items]
Other Income, Net	6,600	3,300
NSTAR Electric Company
Summary of Accounting Policies [Line Items]
Other Income, Net	12,601	8,349
NSTAR Electric Company | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	8,400	5,000
NSTAR Electric Company | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	3,400	1,900
NSTAR Electric Company | Equity in Earnings
Summary of Accounting Policies [Line Items]
Other Income, Net	0	100
NSTAR Electric Company | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net	600	1,200
NSTAR Electric Company | Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	200	100
NSTAR Electric Company | Other
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0
NSTAR Electric Company | Total Other Income, Net
Summary of Accounting Policies [Line Items]
Other Income, Net	12,600	8,300
Public Service Company Of New Hampshire
Summary of Accounting Policies [Line Items]
Other Income, Net	4,749	2,811
Public Service Company Of New Hampshire | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	2,300	1,600
Public Service Company Of New Hampshire | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0
Public Service Company Of New Hampshire | Equity in Earnings
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0
Public Service Company Of New Hampshire | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other Income, Net	0	700
Public Service Company Of New Hampshire | Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	2,400	500
Public Service Company Of New Hampshire | Other
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0
Public Service Company Of New Hampshire | Total Other Income, Net
Summary of Accounting Policies [Line Items]
Other Income, Net	$ 4,700	$ 2,800

SUMMARY OF SIGNIFICANT ACCOUN45

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Gross Tax Receipts [Line Items]
Excise and sales taxes	$ 43.4	$ 42.2
Expenses recorded as taxes other than income taxes	12.7
The Connecticut Light And Power Company
Schedule of Gross Tax Receipts [Line Items]
Excise and sales taxes	$ 35.6	$ 33.9

SUMMARY OF SIGNIFICANT ACCOUN46

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Supplemental Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	$ 274.4	$ 220.5
The Connecticut Light And Power Company
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	117.7	104.2
NSTAR Electric Company
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	59.5	49.4
Public Service Company Of New Hampshire
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	$ 36	$ 28.7

SUMMARY OF SIGNIFICANT ACCOUN47

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	$ 303,810	$ 38,165
Restricted cash included in:
Prepayments and Other Current Assets	35,500	24,400
Marketable Securities	23,300	23,300
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	362,615	85,890	$ 126,285	$ 106,750
The Connecticut Light And Power Company
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	240,217	6,028
Restricted cash included in:
Prepayments and Other Current Assets	3,100	3,100
Marketable Securities	500	500
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	243,839	9,619	18,930	8,403
NSTAR Electric Company
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	9,471	1,763
Restricted cash included in:
Prepayments and Other Current Assets	12,900	12,800
Marketable Securities	100	100
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	22,465	14,708	16,065	15,506
Public Service Company Of New Hampshire
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	2,917	900
Restricted cash included in:
Prepayments and Other Current Assets	11,600	500
Marketable Securities	800	800
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	$ 15,253	$ 2,191	$ 9,116	$ 5,953

REGULATORY ACCOUNTING - Compone

REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 5,338,700	$ 5,239,300
Less: Current Portion	683,211	741,868
Total Long-Term Regulatory Assets	4,655,521	4,497,447
Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	2,033,500	2,068,800
Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	727,100	768,900
Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Total Regulatory Assets	539,600	516,100
Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	544,400	404,800
Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	461,100	509,900
Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	388,000	367,200
Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	361,000	365,200
Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	88,900	101,000
Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	195,100	137,400
The Connecticut Light And Power Company
Regulatory Assets [Line Items]
Total Regulatory Assets	1,729,300	1,645,200
Less: Current Portion	229,735	200,281
Total Long-Term Regulatory Assets	1,499,588	1,444,935
The Connecticut Light And Power Company | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	460,600	469,200
The Connecticut Light And Power Company | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	451,800	453,800
The Connecticut Light And Power Company | Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
The Connecticut Light And Power Company | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	254,400	216,700
The Connecticut Light And Power Company | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	118,000	85,300
The Connecticut Light And Power Company | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	386,500	362,300
The Connecticut Light And Power Company | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
The Connecticut Light And Power Company | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	30,800	30,300
The Connecticut Light And Power Company | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	27,200	27,600
NSTAR Electric Company
Regulatory Assets [Line Items]
Total Regulatory Assets	1,564,300	1,524,500
Less: Current Portion	276,962	333,882
Total Long-Term Regulatory Assets	1,287,282	1,190,575
NSTAR Electric Company | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	549,900	560,700
NSTAR Electric Company | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	115,600	113,200
NSTAR Electric Company | Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric Company | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	246,400	146,600
NSTAR Electric Company | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	221,400	273,000
NSTAR Electric Company | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric Company | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	310,000	313,600
NSTAR Electric Company | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	39,800	39,000
NSTAR Electric Company | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	81,200	78,400
Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Total Regulatory Assets	938,700	940,800
Less: Current Portion	122,481	130,134
Total Long-Term Regulatory Assets	816,194	810,677
Public Service Company Of New Hampshire | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	208,600	212,300
Public Service Company Of New Hampshire | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	20,500	21,700
Public Service Company Of New Hampshire | Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Total Regulatory Assets	539,600	516,100
Public Service Company Of New Hampshire | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	43,600	41,500
Public Service Company Of New Hampshire | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	107,700	116,400
Public Service Company Of New Hampshire | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
Public Service Company Of New Hampshire | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
Public Service Company Of New Hampshire | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	3,400	17,000
Public Service Company Of New Hampshire | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 15,300	$ 15,800

REGULATORY ACCOUNTING - Regulat

REGULATORY ACCOUNTING - Regulatory Costs in Other Long-Term Assets (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	$ 123.3	$ 105.8
Regulatory assets	5,338.7	5,239.3
The Connecticut Light And Power Company
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	21.4	18.2
Regulatory assets	1,729.3	1,645.2
NSTAR Electric Company
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	43.6	42.7
Regulatory assets	1,564.3	1,524.5
Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	38.7	27.2
Regulatory assets	938.7	$ 940.8
Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Regulatory assets	156
Deferred Costs from Generation Asset Sale | The Connecticut Light And Power Company
Regulatory Assets [Line Items]
Regulatory assets	52
Deferred Costs from Generation Asset Sale | NSTAR Electric Company
Regulatory Assets [Line Items]
Regulatory assets	100
Deferred Costs from Generation Asset Sale | Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Regulatory assets	$ 4

REGULATORY ACCOUNTING - Compo50

REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 3,909,700	$ 3,765,400
Less: Current Portion	205,970	128,071
Total Long-Term Regulatory Liabilities	3,703,735	3,637,273
Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	2,895,900	2,882,000
Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	522,800	502,100
Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	128,000	132,300
Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	216,800	136,700
AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	67,600	67,100
Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	26,000	0
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	52,600	45,200
The Connecticut Light And Power Company
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,203,300	1,151,100
Less: Current Portion	66,949	38,967
Total Long-Term Regulatory Liabilities	1,136,361	1,112,136
The Connecticut Light And Power Company | Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,031,600	1,031,600
The Connecticut Light And Power Company | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	34,400	23,200
The Connecticut Light And Power Company | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
The Connecticut Light And Power Company | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	55,900	34,600
The Connecticut Light And Power Company | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	48,500	48,800
The Connecticut Light And Power Company | Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	12,500	0
The Connecticut Light And Power Company | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	20,400	12,900
NSTAR Electric Company
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,619,300	1,594,100
Less: Current Portion	89,230	79,562
Total Long-Term Regulatory Liabilities	1,530,103	1,514,451
NSTAR Electric Company | Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,091,100	1,087,900
NSTAR Electric Company | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	298,500	293,800
NSTAR Electric Company | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	109,000	112,600
NSTAR Electric Company | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	89,200	77,800
NSTAR Electric Company | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	19,100	18,300
NSTAR Electric Company | Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	3,700	0
NSTAR Electric Company | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	8,700	3,700
Public Service Company Of New Hampshire
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	465,200	450,700
Less: Current Portion	15,607	6,251
Total Long-Term Regulatory Liabilities	449,588	444,397
Public Service Company Of New Hampshire | Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	405,100	405,100
Public Service Company Of New Hampshire | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	39,000	37,900
Public Service Company Of New Hampshire | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
Public Service Company Of New Hampshire | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	15,100	5,000
Public Service Company Of New Hampshire | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
Public Service Company Of New Hampshire | Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	3,100	0
Public Service Company Of New Hampshire | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 2,900	$ 2,700

PROPERTY, PLANT AND EQUIPMENT51

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Investment in Utility Property, plant and equipment by asset (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 14,511,000	$ 14,410,500
Distribution - Natural Gas	3,273,200	3,244,200
Transmission - Electric	9,420,900	9,270,900
Distribution - Water	1,556,400	1,558,400
Generation and Solar	36,200	36,200
Utility	28,797,700	28,520,200
Other	698,400	693,700
Property, Plant and Equipment, Gross	29,496,100	29,213,900
Less: Accumulated Depreciation
Utility	(6,927,500)	(6,846,900)
Other	(300,000)	(286,900)
Total Accumulated Depreciation	(7,227,500)	(7,133,800)
Property, Plant and Equipment, Net	22,268,600	22,080,100
Construction Work in Progress	1,690,100	1,537,400
Net Plant	23,958,688	23,617,463
The Connecticut Light And Power Company
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	5,939,900	5,888,300
Transmission - Electric	4,322,600	4,239,900
Generation and Solar	0	0
Property, Plant and Equipment, Gross	10,262,500	10,128,200
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,274,400)	(2,239,000)
Property, Plant and Equipment, Net	7,988,100	7,889,200
Construction Work in Progress	418,500	381,800
Net Plant	8,406,595	8,271,030
NSTAR Electric Company
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	6,532,500	6,479,000
Transmission - Electric	3,842,700	3,821,200
Generation and Solar	36,200	36,200
Property, Plant and Equipment, Gross	10,411,400	10,336,400
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,599,300)	(2,550,200)
Property, Plant and Equipment, Net	7,812,100	7,786,200
Construction Work in Progress	511,700	460,300
Net Plant	8,323,826	8,246,494
Public Service Company Of New Hampshire
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	2,078,900	2,083,400
Transmission - Electric	1,207,100	1,161,300
Generation and Solar	0	0
Property, Plant and Equipment, Gross	3,286,000	3,244,700
Less: Accumulated Depreciation
Total Accumulated Depreciation	(734,900)	(751,800)
Property, Plant and Equipment, Net	2,551,100	2,492,900
Construction Work in Progress	142,900	149,400
Net Plant	$ 2,693,951	$ 2,642,274

DERIVATIVE INSTRUMENTS - Gross

DERIVATIVE INSTRUMENTS - Gross Fair Value of Contracts (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current Derivative Assets | The Connecticut Light And Power Company | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	$ 8.5	$ 9.5
Netting	(6.5)	(7.1)
Net Amount Recorded as a Derivative	2	2.4
Long-term Derivative Assets | The Connecticut Light And Power Company | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	80.2	71.9
Netting	(4.1)	(5.3)
Net Amount Recorded as a Derivative	76.1	66.6
Current Derivative Liabilities | Level 2
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(1.3)	(4.5)
Netting	0.2	0
Net Amount Recorded as a Derivative	(1.1)	(4.5)
Current Derivative Liabilities | The Connecticut Light And Power Company | Level 3
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(49.6)	(54.4)
Netting	0	0
Net Amount Recorded as a Derivative	(49.6)	(54.4)
Long-Term Derivative Liabilities | Level 2
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	(0.4)	(0.4)
Netting	0	0
Net Amount Recorded as a Derivative	(0.4)	(0.4)
Long-Term Derivative Liabilities | The Connecticut Light And Power Company | Level 3
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(415)	(376.9)
Netting	0	0
Net Amount Recorded as a Derivative	$ (415)	$ (376.9)

DERIVATIVE INSTRUMENTS - Deriva

DERIVATIVE INSTRUMENTS - Derivative Contracts at Fair Value (Details) MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)MMBTUMWhMW	Mar. 31, 2017USD ($)	Dec. 31, 2017MMBTU
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts by United Illuminated Company	20.00%
Amount of power to be purchased under capacity-related contract | MW	787
Amount of natural gas to be purchased under futures contracts | MMBTU	5.9		9.5
Gains (losses) on deferred as regulatory costs | $	$ (36.1)	$ (26.5)
The Connecticut Light And Power Company
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts	80.00%
Amount of energy to be purchased under renewable energy contract (in mwh) | MWh	0.1

DERIVATIVE INSTRUMENTS - Unobse

DERIVATIVE INSTRUMENTS - Unobservable Inputs Utilized (Details) - The Connecticut Light And Power Company - Level 3 - $ / KWmo	Mar. 31, 2018	Dec. 31, 2017
Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Capacity Prices (in USDPerKiloWattMonth)	4.30	5
Forward Reserve (in USDPerKiloWattMonth)	0.95	1
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Capacity Prices (in USDPerKiloWattMonth)	5.99	8.70
Forward Reserve (in USDPerKiloWattMonth)	1	2

DERIVATIVE INSTRUMENTS - Unob55

DERIVATIVE INSTRUMENTS - Unobservable Inputs Narrative (Details) - Level 3	3 Months Ended
	Mar. 31, 2018
Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	3.00%
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	16.00%

DERIVATIVE INSTRUMENTS - Deri56

DERIVATIVE INSTRUMENTS - Derivative Assets and Liabilities Measured at Fair Value (Details) - The Connecticut Light And Power Company - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	$ (362.3)	$ (420.5)
Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities	(36.9)	(14.6)
Settlements	12.7	21.6
Fair Value as of End of Period	$ (386.5)	$ (413.5)

MARKETABLE SECURITIES - Schedul

MARKETABLE SECURITIES - Schedule of Available for Sale Securities (Details) - Debt Securities - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 282.1	$ 284.9
Pre-Tax Unrealized Gains	0.8	3.2
Pre-Tax Unrealized Losses	(3.3)	(1.1)
Fair Value	$ 279.6	$ 287

MARKETABLE SECURITIES - Securit

MARKETABLE SECURITIES - Securities Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Marketable securities held in nuclear decommissioning trust	$ 235.7	$ 242.3
Equity securities held in nuclear decommissioning trust	267.3	$ 263.8
Accounting Standards Update 2016-01
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale equity securities	50
Unrealized losses recorded in other income	$ 0.7

MARKETABLE SECURITIES - Sched59

MARKETABLE SECURITIES - Schedule of Contractual Maturities (Details) $ in Millions	Mar. 31, 2018USD ($)
Amortized Cost
Less than one year	$ 36
One to five years	44.6
Six to ten years	63.9
Greater than ten years	137.6
Total Debt Securities	282.1
Fair Value
Less than one year	35.9
One to five years	45.1
Six to ten years	63.3
Greater than ten years	135.3
Total Debt Securities	$ 279.6

MARKETABLE SECURITIES - Sched60

MARKETABLE SECURITIES - Schedule of Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	$ 596.9	$ 600.8
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	340.6	337.1
Level 1 | Mutual Funds and Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	317.3	313.8
Level 1 | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	23.3	23.3
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	256.3	263.7
Level 2 | U.S. Government Issued Debt Securities (Agency and Treasury)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	68	70.2
Level 2 | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	43.7	50.9
Level 2 | Asset-Backed Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	20.7	21.2
Level 2 | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	114.3	110.7
Level 2 | Other Fixed Income Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	$ 9.6	$ 10.7

SHORT-TERM AND LONG-TERM DEBT -

SHORT-TERM AND LONG-TERM DEBT - Commercial Paper Programs and Credit Agreements (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018USD ($)issuance	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Line of Credit Facility [Line Items]
Notes payable to Eversource parent		$ 276,300,000	$ 115,900,000
Long-term debt, current maturities		1,097,288,000	549,631,000
Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity			201,200,000
Line of Credit
Line of Credit Facility [Line Items]
Amount outstanding during period		0	0
Eversource Parent | Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity		1,450,000,000	201,200,000
Short-term debt		$ 682,300,000	$ 979,300,000
Weighted-average interest rate		2.31%	1.86%
Long-term debt, current maturities	$ 446,800,000
Number of debt issuances | issuance	2
Eversource Parent | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 1,450,000,000
Debt instrument term		5 years
NSTAR Electric Company
Line of Credit Facility [Line Items]
Notes payable to Eversource parent			$ 198,000,000
NSTAR Electric Company | Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 650,000,000
Short-term debt		$ 367,000,000	$ 234,000,000
Weighted-average interest rate		1.75%	1.55%
NSTAR Electric Company | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 650,000,000
Debt instrument term		5 years
Aquarion | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 100,000,000
Amount outstanding during period		$ 0
Short-term debt			76,000,000
The Connecticut Light And Power Company
Line of Credit Facility [Line Items]
Notes payable to Eversource parent		0	69,500,000
Long-term debt, current maturities		550,000,000	300,000,000
Public Service Company Of New Hampshire
Line of Credit Facility [Line Items]
Notes payable to Eversource parent		271,300,000	262,900,000
Long-term debt, current maturities		$ 110,000,000	$ 110,000,000

SHORT-TERM AND LONG-TERM DEBT62

SHORT-TERM AND LONG-TERM DEBT - Schedule of Commercial Paper Program (Details) - Commercial Paper - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
NSTAR Electric Company
Debt Instrument [Line Items]
Borrowings Outstanding	$ 367	$ 234
Available Borrowing Capacity	$ 283	$ 416
Weighted-Average Interest Rate	1.75%	1.55%
Eversource Parent
Debt Instrument [Line Items]
Borrowings Outstanding	$ 682.3	$ 979.3
Available Borrowing Capacity	$ 767.7	$ 470.7
Weighted-Average Interest Rate	2.31%	1.86%

SHORT-TERM AND LONG-TERM DEBT63

SHORT-TERM AND LONG-TERM DEBT - Schedule of Issuances and Repayments (Details) - USD ($)	1 Months Ended			3 Months Ended
	Jan. 31, 2015	May 31, 2013	May 31, 2008	Mar. 31, 2018	Mar. 31, 2017	Jan. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Repayments				$ (150,218,000)	$ (150,000,000)
The Connecticut Light And Power Company
Debt Instrument [Line Items]
Repayments				0	$ (150,000,000)
The Connecticut Light And Power Company | Senior Notes | 4.00% 2018 Series A First Mortgage Bonds
Debt Instrument [Line Items]
Issuances				$ 500,000,000
Interest rate, stated percentage				4.00%
The Connecticut Light And Power Company | Senior Notes | 2008 Series A First Mortgage Bonds Due 2018
Debt Instrument [Line Items]
Repayments			$ (300,000,000)
Interest rate, stated percentage			5.65%
Public Service Company Of New Hampshire | Senior Notes | 2008 Series O First Mortgage Bonds Due 2018
Debt Instrument [Line Items]
Repayments			$ (110,000,000)
Interest rate, stated percentage			6.00%
Eversource Parent | Senior Notes | Eversource Parent 2.50% Series I Senior Notes
Debt Instrument [Line Items]
Issuances						$ 200,000,000
Long-term debt							$ 450,000,000
Interest rate, stated percentage						2.50%
Eversource Parent | Senior Notes | 3.30% Series M Senior Notes
Debt Instrument [Line Items]
Issuances						$ 450,000,000
Interest rate, stated percentage						3.30%
Eversource Parent | Senior Notes | Eversource Parent 1.60% Series G Senior Notes
Debt Instrument [Line Items]
Repayments	$ (150,000,000)
Interest rate, stated percentage	1.60%
Eversource Parent | Senior Notes | Series E Senior Notes Due 2018
Debt Instrument [Line Items]
Repayments		$ (300,000,000)
Interest rate, stated percentage		1.45%

PENSION BENEFITS AND POSTRETI64

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION - Components of Periodic Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 22.7	$ 18.7
Interest Cost	48.4	46.3
Expected Return on Pension Plan Assets	(98)	(83.5)
Actuarial Loss	36	33.6
Prior Service Cost/(Credit)	2.2	1.1
Total Net Periodic Benefit Income	11.3	16.2
Capitalized PBOP Income/ Pension Expense	7.5	5.4
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.7	2.4
Interest Cost	7.6	7.2
Expected Return on Pension Plan Assets	(18.1)	(15.9)
Actuarial Loss	2.6	2
Prior Service Cost/(Credit)	(5.9)	(5.3)
Total Net Periodic Benefit Income	(11.1)	(9.6)
Capitalized PBOP Income/ Pension Expense	0.8	(4.6)
The Connecticut Light And Power Company | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	5.7	4.8
Interest Cost	10.6	10.5
Expected Return on Pension Plan Assets	(20.8)	(18)
Actuarial Loss	7.4	6.9
Prior Service Cost/(Credit)	0.4	0.4
Total Net Periodic Benefit Income	3.3	4.6
Intercompany Allocations	1.4	2.5
Capitalized PBOP Income/ Pension Expense	2.3	2.5
The Connecticut Light And Power Company | Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.5	0.5
Interest Cost	1.4	1.4
Expected Return on Pension Plan Assets	(2.6)	(2.4)
Actuarial Loss	0.3	0.2
Prior Service Cost/(Credit)	0.3	0.3
Total Net Periodic Benefit Income	(0.1)	0
Intercompany Allocations	(0.3)	(0.3)
Capitalized PBOP Income/ Pension Expense	0.2	(0.1)
NSTAR Electric Company | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	4.7	4.1
Interest Cost	10.8	10.4
Expected Return on Pension Plan Assets	(25.2)	(22)
Actuarial Loss	10.5	10.1
Prior Service Cost/(Credit)	0.2	0.2
Total Net Periodic Benefit Income	1	2.8
Intercompany Allocations	1.5	2.4
Capitalized PBOP Income/ Pension Expense	2.1	1.8
NSTAR Electric Company | Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.5	0.5
Interest Cost	2.2	2.4
Expected Return on Pension Plan Assets	(8.1)	(7.1)
Actuarial Loss	0.7	0.9
Prior Service Cost/(Credit)	(4.3)	(4.3)
Total Net Periodic Benefit Income	(9)	(7.6)
Intercompany Allocations	(0.3)	(0.3)
Capitalized PBOP Income/ Pension Expense	0.2	(3.8)
Public Service Company Of New Hampshire | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.9	2.5
Interest Cost	5.3	5.2
Expected Return on Pension Plan Assets	(10.9)	(9.9)
Actuarial Loss	3.3	2.8
Prior Service Cost/(Credit)	0.1	0.1
Total Net Periodic Benefit Income	0.7	0.7
Intercompany Allocations	0.5	0.8
Capitalized PBOP Income/ Pension Expense	0.8	0.3
Public Service Company Of New Hampshire | Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.3	0.3
Interest Cost	0.8	0.8
Expected Return on Pension Plan Assets	(1.5)	(1.3)
Actuarial Loss	0.2	0.1
Prior Service Cost/(Credit)	0.1	0.1
Total Net Periodic Benefit Income	(0.1)	0
Intercompany Allocations	(0.1)	(0.1)
Capitalized PBOP Income/ Pension Expense	$ 0.1	$ 0

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Schedule of Environmental Matters (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)site	Dec. 31, 2017USD ($)site
Site Contingency [Line Items]
Number of Sites | site	58	59
Reserve | $	$ 63.8	$ 54.9
The Connecticut Light And Power Company
Site Contingency [Line Items]
Number of Sites | site	14	14
Reserve | $	$ 5.1	$ 4.7
NSTAR Electric Company
Site Contingency [Line Items]
Number of Sites | site	15	15
Reserve | $	$ 2.8	$ 2.7
Public Service Company Of New Hampshire
Site Contingency [Line Items]
Number of Sites | site	9	10
Reserve | $	$ 5.6	$ 5.7

COMMITMENTS AND CONTINGENCIES66

COMMITMENTS AND CONTINGENCIES - Environmental Matters Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Site Contingency [Line Items]
Reserve	$ 63.8	$ 54.9
MGP Site accrual
Site Contingency [Line Items]
Reserve	$ 57.8	$ 49

COMMITMENTS AND CONTINGENCIES67

COMMITMENTS AND CONTINGENCIES - Guarantees and Indemnifications Narrative (Details)	Dec. 31, 2017USD ($)
Guarantee Of Financial Obligations Of Npt
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure (up to)	$ 25,000,000
Guarantee Of Npt Letters Of Credit
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure (up to)	$ 14,000,000

COMMITMENTS AND CONTINGENCIES68

COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) $ in Millions	Mar. 31, 2018USD ($)
Eversource Gas Transmission LLC
Loss Contingencies [Line Items]
Maximum Exposure	$ 185
Various
Loss Contingencies [Line Items]
Maximum Exposure	41.2
Eversource Service and Rocky River Realty Company
Loss Contingencies [Line Items]
Maximum Exposure	$ 7.3

COMMITMENTS AND CONTINGENCIES69

COMMITMENTS AND CONTINGENCIES - Spent Nuclear Fuel Obligations , Yankee Companies (Details) $ in Millions	May 22, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Damages sought, value	$ 100

COMMITMENTS AND CONTINGENCIES70

COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) - USD ($) $ in Millions	Mar. 27, 2018	Oct. 06, 2017	Jun. 08, 2017	Apr. 14, 2017	Apr. 29, 2016	Mar. 31, 2018	Mar. 26, 2014	Apr. 14, 2017
FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Base ROE percentage challenged by complainants			11.14%			11.14%
Percentage of maximum ROE for any incentive project			13.50%
FERC ROE Complaints
Loss Contingencies [Line Items]
Period of complaint						15 months
Basis point change						10.00%
Estimate of possible loss for each 10 basis point change to base ROE						$ 3
FERC ROE Fourth Complaint
Loss Contingencies [Line Items]
Base ROE percentage of complaint period	10.57%				10.57%
Maximum percentage cap of ROE for incentive projects	11.74%				11.74%
Percentage of maximum ROE for any incentive project		10.57%
Loss contingency, estimate of possible earnings impact						0
FERC ROE First Complaint
Loss Contingencies [Line Items]
Base ROE percentage challenged by complainants				11.14%
Percentage of maximum ROE for any incentive project								11.74%
Loss contingency, estimate of possible earnings impact						0
FERC ROE Second Complaint
Loss Contingencies [Line Items]
Base ROE percentage of complaint period							10.57%
Percentage of maximum ROE for any incentive project							11.74%
Loss contingency, estimate of possible earnings impact						39.1
NSTAR Electric Company | FERC ROE Second Complaint
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact						$ 14.6

COMMITMENTS AND CONTINGENCIES71

COMMITMENTS AND CONTINGENCIES - Schedule of Complaints and Base ROEs (Details) - USD ($) $ in Millions	Mar. 27, 2018	Oct. 06, 2017	Jun. 08, 2017	Apr. 29, 2016	Mar. 31, 2018	Jul. 28, 2017	Mar. 26, 2014	Dec. 31, 2012	Oct. 30, 2015	Apr. 14, 2017	Oct. 15, 2014
FERC ROE First Complaint
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)								11.14%
Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (as a percentage)								10.57%		10.57%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					$ 0
Percentage of maximum ROE for any incentive project										11.74%
Customer refund payments					38.9
FERC ROE Second Complaint
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)							11.14%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					39.1
FERC ALJ Recommendation of base ROE on Second and Third Complaints (Issued March 22, 2016) (in percentage)							9.59%
Percentage of maximum ROE for any incentive project							11.74%
Base ROE percentage of complaint period							10.57%
FERC ROE Third Complaint
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)									11.14%
Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (as a percentage)									10.57%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					0
FERC ALJ Recommendation of base ROE on Second and Third Complaints (Issued March 22, 2016) (in percentage)									10.90%
FERC ROE Fourth Complaint
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)		11.74%				10.57%
Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (as a percentage)						10.57%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					0
FERC ALJ Recommendation of base ROE on Second and Third Complaints (Issued March 22, 2016) (in percentage)						10.57%
Percentage of maximum ROE for any incentive project		10.57%
Base ROE percentage of complaint period	10.57%			10.57%
FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project			13.50%
The Connecticut Light And Power Company | FERC ROE First Complaint
Loss Contingencies [Line Items]
Customer refund payments					22.4
The Connecticut Light And Power Company | FERC ROE Second Complaint
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					21.4
NSTAR Electric Company | FERC ROE First Complaint
Loss Contingencies [Line Items]
Customer refund payments					13.7
NSTAR Electric Company | FERC ROE Second Complaint
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					14.6
Public Service Company Of New Hampshire | FERC ROE First Complaint
Loss Contingencies [Line Items]
Customer refund payments					2.8
Public Service Company Of New Hampshire | FERC ROE Second Complaint
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2018 (in millions)					$ 3.1
Minimum | FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project											11.14%
Maximum | FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project											13.10%

COMMITMENTS AND CONTINGENCIES72

COMMITMENTS AND CONTINGENCIES - Harbor Civil Action (Details) $ in Millions	Jul. 15, 2016MW	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Loss Contingencies [Line Items]
Amount of capacity required for installation of distribution cable (in volts) | MW	0.115
NSTAR Electric Company
Loss Contingencies [Line Items]
Charge relating to assets previously recognized as capital		$ 4.9
Base rate credit for new cable		17.5
Loss contingency accrual		$ 2.1	$ 11.1

ASSETS HELD FOR SALE - Narrativ

ASSETS HELD FOR SALE - Narrative (Details) - USD ($) $ in Thousands	Jan. 30, 2018	Jan. 10, 2018	Oct. 11, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Regulatory Assets [Line Items]
Regulatory assets held for sale				$ 5,338,700		$ 5,239,300
Pre-tax income associated with assets held for sale				355,192	$ 419,167
Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Thermal generation assets			$ 175,000
Hydroelectric assets			$ 83,000
Purchase price in purchase sale agreement		$ 40,900
Proceeds from purchase and sale agreement		$ 134,100
Regulatory assets held for sale				938,700		940,800
Difference between book value of hydroelectric generation assets and expected proceeds from sale				23,000
Rate reduction bonds issued	$ 690,000
Pre-tax income associated with assets held for sale				47,744	56,642
Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Regulatory assets held for sale				539,600		516,100
Deferred Costs from Generation Asset Sale | Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Regulatory assets held for sale				539,600		$ 516,100
Domestic Tax Authority | Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Pre-tax income associated with assets held for sale				$ 5,900	$ 14,800

ASSETS HELD FOR SALE - Generati

ASSETS HELD FOR SALE - Generation Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Accumulated Depreciation	$ (7,227,500)	$ (7,133,800)
Net Plant	23,958,688	23,617,463
Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Accumulated Depreciation	(734,900)	(751,800)
Net Plant	2,693,951	$ 2,642,274
Electricity Generation Plant, Non-Nuclear | Public Service Company Of New Hampshire
Regulatory Assets [Line Items]
Hydroelectric Gross Plant	86,600
Accumulated Depreciation	(27,400)
Net Plant	59,200
Materials and Supplies	100
Total Generation Assets	$ 59,300

FAIR VALUE OF FINANCIAL INSTR75

FAIR VALUE OF FINANCIAL INSTRUMENTS - Carrying Amounts and Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	$ 155,570	$ 155,570
Carrying Amount | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	155,600	155,600
Long-Term Debt	13,113,300	12,325,500
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	165,800	160,800
Long-Term Debt	13,376,100	12,877,100
The Connecticut Light And Power Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
The Connecticut Light And Power Company | Carrying Amount | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
Long-Term Debt	3,553,600	3,059,100
The Connecticut Light And Power Company | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	122,300	116,500
Long-Term Debt	3,821,900	3,430,500
NSTAR Electric Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
NSTAR Electric Company | Carrying Amount | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
Long-Term Debt	2,943,900	2,943,800
NSTAR Electric Company | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,500	44,300
Long-Term Debt	3,071,700	3,156,500
Public Service Company Of New Hampshire | Carrying Amount | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	1,001,800	1,002,400
Public Service Company Of New Hampshire | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	$ 1,025,200	$ 1,038,200

ACCUMULATED OTHER COMPREHENSI76

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Accumulated Other Comprehensive Income (loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AOCI Attributable to Parent [Roll Forward]
Beginning balance	$ 11,086,242
OCI Before Reclassifications		$ 1,700
Amounts Reclassified from AOCI		1,500
Net OCI	3,273	3,141
Ending balance	11,183,714
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(66,400)	(65,300)
OCI Before Reclassifications	(400)
Amounts Reclassified from AOCI	3,700
Net OCI	3,300
Ending balance	(63,100)	(62,100)
Qualified Cash Flow Hedging Instruments
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(6,200)	(8,200)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCI	700	500
Net OCI	700	500
Ending balance	(5,500)	(7,700)
Unrealized Losses on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance	0	400
OCI Before Reclassifications	(400)	1,700
Amounts Reclassified from AOCI	0	0
Net OCI	(400)	1,700
Ending balance	(400)	2,100
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(60,200)	(57,500)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCI	3,000	1,000
Net OCI	3,000	1,000
Ending balance	$ (57,200)	$ (56,500)

COMMON SHARES - Schedule of Com

COMMON SHARES - Schedule of Common Shares (Details) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 5	$ 5
Authorized (in shares)	380,000,000	380,000,000
Issued (in shares)	333,878,402	333,878,402
The Connecticut Light And Power Company
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 10	$ 10
Authorized (in shares)	24,500,000	24,500,000
Issued (in shares)	6,035,205	6,035,205
NSTAR Electric Company
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 1	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	200	200
Public Service Company Of New Hampshire
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 1	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	301	301

COMMON SHARES - Narrative (Deta

COMMON SHARES - Narrative (Details) - shares	Mar. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Treasury stock (in shares)	16,992,594	16,992,594
Common stock outstanding (in shares)	316,885,808	316,885,808

COMMON SHAREHOLDERS' EQUITY A79

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Equity [Abstract]
Net income attributable to noncontrolling interests	$ 1,900	$ 1,900
Noncontrolling Interest – Preferred Stock of Subsidiaries	$ 155,570		$ 155,570

EARNINGS PER SHARE - Narrative

EARNINGS PER SHARE - Narrative (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Antidilutive share awards excluded from computation (in shares)	0	0

EARNINGS PER SHARE - Schedule o

EARNINGS PER SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 269,546	$ 259,458
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,397,052	317,463,151
Dilutive Effect (in shares)	595,947	661,385
Diluted (in shares)	317,992,999	318,124,536
Basic and Diluted EPS (in dollars per share)	$ 0.85	$ 0.82

REVENUES - Schedule of Revenue

REVENUES - Schedule of Revenue from Contract with Customer (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	$ 2,277,100
Operating Revenues	2,287,962	$ 2,105,135
Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,269,700
Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	759,900
Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	109,500
Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	2,139,100
Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	65,000
Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	77,100
Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	21,900
Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	26,000
Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	6,600
Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	4,300
Eliminations
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(482,600)
Operating Revenues	(472,000)
Eliminations | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Eliminations | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Eliminations | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(2,500)
Eliminations | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(2,500)
Eliminations | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(258,700)
Eliminations | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Eliminations | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(221,400)
Eliminations | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Eliminations | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	10,600
Eliminations | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0
The Connecticut Light And Power Company
Disaggregation of Revenue [Line Items]
Operating Revenues	784,983	732,310
The Connecticut Light And Power Company | Eliminations
Disaggregation of Revenue [Line Items]
Operating Revenues	(109,000)
NSTAR Electric Company
Disaggregation of Revenue [Line Items]
Operating Revenues	770,127	733,808
NSTAR Electric Company | Eliminations
Disaggregation of Revenue [Line Items]
Operating Revenues	(93,100)
Public Service Company Of New Hampshire
Disaggregation of Revenue [Line Items]
Operating Revenues	267,350	253,157
Public Service Company Of New Hampshire | Eliminations
Disaggregation of Revenue [Line Items]
Operating Revenues	(36,400)
Operating Segments | Electric Distribution
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,742,500
Operating Revenues	1,754,600	1,401,100
Operating Segments | Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	994,400
Operating Segments | Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	611,400
Operating Segments | Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	81,500
Operating Segments | Electric Distribution | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,687,300
Operating Segments | Electric Distribution | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Distribution | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	58,500
Operating Segments | Electric Distribution | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	16,000
Operating Segments | Electric Distribution | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	19,300
Operating Segments | Electric Distribution | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	8,700
Operating Segments | Electric Distribution | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	3,400
Operating Segments | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	425,800
Operating Revenues	424,900	403,600
Operating Segments | Natural Gas Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	248,900
Operating Segments | Natural Gas Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	134,700
Operating Segments | Natural Gas Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	29,500
Operating Segments | Natural Gas Distribution | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	413,100
Operating Segments | Natural Gas Distribution | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Natural Gas Distribution | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	17,800
Operating Segments | Natural Gas Distribution | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(600)
Operating Segments | Natural Gas Distribution | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	4,500
Operating Segments | Natural Gas Distribution | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(1,700)
Operating Segments | Natural Gas Distribution | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	800
Operating Segments | Electric Transmission
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	316,700
Operating Revenues	305,000	316,900
Operating Segments | Electric Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Transmission | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Transmission | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	313,600
Operating Segments | Electric Transmission | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Transmission | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	3,100
Operating Segments | Electric Transmission | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Electric Transmission | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(11,700)
Operating Segments | Electric Transmission | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0
Operating Segments | Water Distribution
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	43,800
Operating Revenues	44,600	$ 0
Operating Segments | Water Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	26,400
Operating Segments | Water Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	13,800
Operating Segments | Water Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,000
Operating Segments | Water Distribution | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	41,200
Operating Segments | Water Distribution | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Water Distribution | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	800
Operating Segments | Water Distribution | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	4,000
Operating Segments | Water Distribution | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	2,200
Operating Segments | Water Distribution | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	700
Operating Segments | Water Distribution | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	100
Operating Segments | Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	230,900
Operating Revenues	230,900
Operating Segments | Other | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Other | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Other | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Other | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Other | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	10,100
Operating Segments | Other | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Other | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	220,800
Operating Segments | Other | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0
Operating Segments | Other | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0
Operating Segments | Other | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0
Operating Segments | The Connecticut Light And Power Company
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	897,800
Operating Revenues	785,000
Operating Segments | The Connecticut Light And Power Company | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	483,400
Operating Segments | The Connecticut Light And Power Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	222,500
Operating Segments | The Connecticut Light And Power Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	35,800
Operating Segments | The Connecticut Light And Power Company | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	741,700
Operating Segments | The Connecticut Light And Power Company | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	150,800
Operating Segments | The Connecticut Light And Power Company | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	10,300
Operating Segments | The Connecticut Light And Power Company | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	7,500
Operating Segments | The Connecticut Light And Power Company | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	12,500
Operating Segments | The Connecticut Light And Power Company | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(5,100)
Operating Segments | The Connecticut Light And Power Company | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	1,300
Operating Segments | NSTAR Electric Company
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	854,800
Operating Revenues	770,100
Operating Segments | NSTAR Electric Company | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	364,200
Operating Segments | NSTAR Electric Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	314,400
Operating Segments | NSTAR Electric Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	28,100
Operating Segments | NSTAR Electric Company | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	706,700
Operating Segments | NSTAR Electric Company | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	118,600
Operating Segments | NSTAR Electric Company | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	24,900
Operating Segments | NSTAR Electric Company | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	8,300
Operating Segments | NSTAR Electric Company | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	3,700
Operating Segments | NSTAR Electric Company | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	6,700
Operating Segments | NSTAR Electric Company | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	1,700
Operating Segments | Public Service Company Of New Hampshire
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	308,000
Operating Revenues	267,400
Operating Segments | Public Service Company Of New Hampshire | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	146,800
Operating Segments | Public Service Company Of New Hampshire | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	74,900
Operating Segments | Public Service Company Of New Hampshire | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	17,600
Operating Segments | Public Service Company Of New Hampshire | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	239,300
Operating Segments | Public Service Company Of New Hampshire | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	44,200
Operating Segments | Public Service Company Of New Hampshire | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	24,100
Operating Segments | Public Service Company Of New Hampshire | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	3,500
Operating Segments | Public Service Company Of New Hampshire | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	3,100
Operating Segments | Public Service Company Of New Hampshire | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(4,600)
Operating Segments | Public Service Company Of New Hampshire | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	$ 400

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)segmentcompany
Segment Reporting Information [Line Items]
Number of companies that transmit hydro electricity imported from The Hydro-Quebec System in Canada | company	2
Amount of natural gas transmission purchased from Enbridge by Yankee Gas and NSTAR Gas | $	$ 62.5
The Connecticut Light And Power Company
Segment Reporting Information [Line Items]
Number of reportable segments	1
NSTAR Electric Company
Segment Reporting Information [Line Items]
Number of reportable segments	1
Public Service Company Of New Hampshire
Segment Reporting Information [Line Items]
Number of reportable segments	1

REVENUES - Narrative (Details)

REVENUES - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Revenue from External Customer [Line Items]
Revenue reserve	$ 2,277.1
Reserve for Revenue Subject to Refund
Revenue from External Customer [Line Items]
Revenue reserve	$ 26

SEGMENT INFORMATION - Schedule

SEGMENT INFORMATION - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,287,962	$ 2,105,135
Depreciation and Amortization	(249,500)	(210,800)
Other Operating Expenses	(1,596,000)	(1,393,300)
Operating Income/(Loss)	442,532	500,977
Interest Expense	(121,100)	103,400
Other Income, Net	33,789	21,619
Net Income Attributable to Common Shareholders	269,546	259,458
Cash Flows Used for Investments in Plant	607,334	523,560
Assets	37,039,983		$ 36,220,386
Operating Segments | Electric Distribution
Segment Reporting Information [Line Items]
Operating Revenues	1,754,600	1,401,100
Depreciation and Amortization	(144,400)	(129,800)
Other Operating Expenses	(1,443,500)	(1,048,900)
Operating Income/(Loss)	166,700	222,400
Interest Expense	(47,400)	48,200
Other Income, Net	19,600	12,000
Net Income Attributable to Common Shareholders	104,200	114,100
Cash Flows Used for Investments in Plant	236,000	236,200
Assets	21,167,900		19,250,400
Operating Segments | Natural Gas Distribution
Segment Reporting Information [Line Items]
Operating Revenues	424,900	403,600
Depreciation and Amortization	(26,400)	(21,700)
Other Operating Expenses	(312,600)	(290,200)
Operating Income/(Loss)	85,900	91,700
Interest Expense	(11,100)	10,600
Other Income, Net	2,000	900
Net Income Attributable to Common Shareholders	57,800	50,800
Cash Flows Used for Investments in Plant	70,400	64,500
Assets	3,636,800		3,595,200
Operating Segments | Electric Transmission
Segment Reporting Information [Line Items]
Operating Revenues	305,000	316,900
Depreciation and Amortization	(56,600)	(50,600)
Other Operating Expenses	(83,200)	(90,200)
Operating Income/(Loss)	165,200	176,100
Interest Expense	(29,700)	28,100
Other Income, Net	8,000	5,100
Net Income Attributable to Common Shareholders	107,400	94,200
Cash Flows Used for Investments in Plant	239,200	192,600
Assets	9,833,200		9,401,200
Operating Segments | Water Distribution
Segment Reporting Information [Line Items]
Operating Revenues	44,600	0
Depreciation and Amortization	(10,700)	0
Other Operating Expenses	(23,900)	0
Operating Income/(Loss)	10,000	0
Interest Expense	(8,400)	0
Other Income, Net	(600)	0
Net Income Attributable to Common Shareholders	1,500	0
Cash Flows Used for Investments in Plant	19,000	0
Assets	2,487,900		2,470,000
Operating Segments | Other
Segment Reporting Information [Line Items]
Operating Revenues	230,900	236,300
Depreciation and Amortization	(12,000)	(9,200)
Other Operating Expenses	(204,700)	(216,800)
Operating Income/(Loss)	14,200	10,300
Interest Expense	(31,900)	19,700
Other Income, Net	360,100	329,100
Net Income Attributable to Common Shareholders	346,000	322,200
Cash Flows Used for Investments in Plant	42,700	30,300
Assets	16,586,500		15,933,800
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(472,000)	(252,800)
Depreciation and Amortization	600	500
Other Operating Expenses	471,900	252,800
Operating Income/(Loss)	500	500
Interest Expense	7,400	(3,200)
Other Income, Net	(355,300)	(325,500)
Net Income Attributable to Common Shareholders	(347,400)	(321,800)
Cash Flows Used for Investments in Plant	0	$ 0
Assets	$ (16,672,300)		$ (14,430,200)

ACQUISITION OF AQUARION - Narra

ACQUISITION OF AQUARION - Narrative (Details) - USD ($) $ in Millions	Dec. 04, 2017	Jun. 02, 2017	Mar. 31, 2018
Aquarion Water Company
Business Acquisition [Line Items]
Consideration transferred		$ 1,675
Payments to acquire businesses	$ 880	880
Consideration transferred, liabilities incurred		$ 795
Equity interest	745
Aquarion shareholder loan paid at closing	$ 135
Line of Credit | Aquarion
Business Acquisition [Line Items]
Long-term debt, fair value			$ 7.9

ACQUISITION OF AQUARION - Sched

ACQUISITION OF AQUARION - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 4,427,266	$ 4,427,266
Aquarion Water Company
Business Acquisition [Line Items]
Current Assets	41,200
PP&E	1,034,900
Goodwill	907,900
Other Noncurrent Assets, excluding Goodwill	215,500
Current Liabilities	(121,900)
Noncurrent Liabilities	(421,600)
Long-Term Debt	(778,300)
Total Cash Purchase Price	$ 877,700