The Connecticut Light and Power Company (CNLPM) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 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	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Smaller Reporting Company	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 ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and Cash Equivalents	$ 59,092	$ 38,165
Receivables, Net	1,091,589	925,083
Unbilled Revenues	170,044	201,361
Materials, Supplies and Inventory	192,508	223,063
Regulatory Assets	436,704	741,868
Prepayments and Other Current Assets	203,434	138,009
Assets Held for Sale	0	219,550
Total Current Assets	2,153,371	2,487,099
Property, Plant and Equipment, Net	24,967,702	23,617,463
Deferred Debits and Other Assets:
Regulatory Assets	4,716,631	4,497,447
Goodwill	4,427,266	4,427,266
Marketable Securities	585,960	585,419
Other Long-Term Assets	664,739	605,692
Total Deferred Debits and Other Assets	10,394,596	10,115,824
Total Assets	37,515,669	36,220,386
Current Liabilities:
Notes Payable	1,067,200	1,088,087
Long-Term Debt – Current Portion	387,310	549,631
Rate Reduction Bonds – Current Portion	52,332	0
Accounts Payable	962,298	1,085,034
Obligations to Third Party Suppliers	199,762	144,046
Regulatory Liabilities	344,708	128,071
Other Current Liabilities	616,662	594,176
Total Current Liabilities	3,630,272	3,589,045
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	3,386,324	3,297,518
Regulatory Liabilities	3,706,792	3,637,273
Derivative Liabilities	385,865	377,257
Accrued Pension, SERP and PBOP	1,013,182	1,228,091
Other Long-Term Liabilities	1,094,019	1,073,501
Total Deferred Credits and Other Liabilities	9,586,182	9,613,640
Long-Term Debt	12,151,536	11,775,889
Rate Reduction Bonds	583,331	0
Noncontrolling Interest – Preferred Stock of Subsidiaries	155,570	155,570
Common Shareholders' Equity:
Common Shares	1,669,392	1,669,392
Capital Surplus, Paid In	6,234,044	6,239,940
Retained Earnings	3,882,695	3,561,084
Accumulated Other Comprehensive Loss	(59,582)	(66,403)
Treasury Stock	(317,771)	(317,771)
Common Stockholder's Equity	11,408,778	11,086,242
Total Liabilities and Capitalization	37,515,669	36,220,386
The Connecticut Light and Power Company
Current Assets:
Cash and Cash Equivalents	977	6,028
Receivables, Net	466,768	370,676
Accounts Receivable from Affiliated Companies	32,074	28,181
Unbilled Revenues	53,690	54,154
Materials, Supplies and Inventory	45,757	48,438
Regulatory Assets	128,793	200,281
Prepaid Property Taxes	60,532	17,884
Prepayments and Other Current Assets	15,470	29,042
Total Current Assets	804,061	754,684
Property, Plant and Equipment, Net	8,753,744	8,271,030
Deferred Debits and Other Assets:
Regulatory Assets	1,545,012	1,444,935
Other Long-Term Assets	175,488	159,597
Total Deferred Debits and Other Assets	1,720,500	1,604,532
Total Assets	11,278,305	10,630,246
Current Liabilities:
Notes Payable to Eversource Parent	45,900	69,500
Long-Term Debt – Current Portion	250,000	300,000
Accounts Payable	347,443	367,605
Accounts Payable to Affiliated Companies	86,772	82,201
Obligations to Third Party Suppliers	64,283	52,860
Accrued Taxes	78,507	21,665
Regulatory Liabilities	126,574	38,967
Other Current Liabilities	152,147	159,961
Total Current Liabilities	1,151,626	1,092,759
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,136,221	1,103,367
Regulatory Liabilities	1,131,234	1,112,136
Derivative Liabilities	385,779	376,918
Accrued Pension, SERP and PBOP	301,946	354,469
Other Long-Term Liabilities	130,069	128,135
Total Deferred Credits and Other Liabilities	3,085,249	3,075,025
Long-Term Debt	3,003,625	2,759,135
Noncontrolling Interest – Preferred Stock of Subsidiaries	116,200	116,200
Common Shareholders' Equity:
Common Shares	60,352	60,352
Capital Surplus, Paid In	2,210,765	2,110,765
Retained Earnings	1,650,182	1,415,741
Accumulated Other Comprehensive Loss	306	269
Common Stockholder's Equity	3,921,605	3,587,127
Total Liabilities and Capitalization	11,278,305	10,630,246
NSTAR Electric Company
Current Assets:
Cash and Cash Equivalents	2,367	1,763
Receivables, Net	457,695	341,341
Accounts Receivable from Affiliated Companies	43,767	40,723
Unbilled Revenues	55,046	49,865
Materials, Supplies and Inventory	66,361	95,517
Regulatory Assets	193,541	333,882
Prepayments and Other Current Assets	18,128	24,499
Total Current Assets	836,905	887,590
Property, Plant and Equipment, Net	8,576,096	8,246,494
Deferred Debits and Other Assets:
Regulatory Assets	1,226,811	1,190,575
Prepaid PBOP	153,142	126,948
Other Long-Term Assets	107,208	84,766
Total Deferred Debits and Other Assets	1,487,161	1,402,289
Total Assets	10,900,162	10,536,373
Current Liabilities:
Notes Payable	240,500	234,000
Notes Payable to Eversource Parent	16,000	0
Accounts Payable	296,208	340,115
Accounts Payable to Affiliated Companies	77,329	91,260
Obligations to Third Party Suppliers	133,865	88,721
Renewable Portfolio Standards Compliance Obligations	100,782	111,524
Regulatory Liabilities	168,225	79,562
Other Current Liabilities	113,728	79,916
Total Current Liabilities	1,146,637	1,025,098
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,279,302	1,275,814
Regulatory Liabilities	1,566,285	1,514,451
Accrued Pension, SERP and PBOP	6,171	89,995
Other Long-Term Liabilities	219,050	198,176
Total Deferred Credits and Other Liabilities	3,070,808	3,078,436
Long-Term Debt	2,944,616	2,943,759
Noncontrolling Interest – Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,608,442	1,502,942
Retained Earnings	2,088,157	1,944,961
Accumulated Other Comprehensive Loss	(1,498)	(1,823)
Common Stockholder's Equity	3,695,101	3,446,080
Total Liabilities and Capitalization	10,900,162	10,536,373
Public Service Company of New Hampshire
Current Assets:
Cash and Cash Equivalents	7,462	900
Receivables, Net	115,706	92,774
Accounts Receivable from Affiliated Companies	20,007	5,297
Unbilled Revenues	39,760	49,448
Materials, Supplies and Inventory	39,877	40,285
Regulatory Assets	61,379	130,134
Special Deposits	26,863	728
Prepayments and Other Current Assets	7,600	28,203
Assets Held for Sale	0	219,550
Total Current Assets	318,654	567,319
Property, Plant and Equipment, Net	2,826,541	2,642,274
Deferred Debits and Other Assets:
Regulatory Assets	892,075	810,677
Other Long-Term Assets	19,252	42,391
Total Deferred Debits and Other Assets	911,327	853,068
Total Assets	4,056,522	4,062,661
Current Liabilities:
Notes Payable to Eversource Parent	46,600	262,900
Long-Term Debt – Current Portion	0	110,000
Rate Reduction Bonds – Current Portion	52,332	0
Accounts Payable	118,523	128,685
Accounts Payable to Affiliated Companies	35,699	24,676
Dividends Payable to Eversource Parent	0	150,000
Accrued Interest	19,615	6,722
Renewable Portfolio Standards Compliance Obligations	29,867	27,765
Regulatory Liabilities	39,661	6,251
Other Current Liabilities	34,790	33,437
Total Current Liabilities	377,087	750,436
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	457,512	443,468
Regulatory Liabilities	433,822	444,397
Accrued Pension, SERP and PBOP	126,839	124,639
Other Long-Term Liabilities	35,901	56,689
Total Deferred Credits and Other Liabilities	1,054,074	1,069,193
Long-Term Debt	894,100	892,438
Rate Reduction Bonds	583,331	0
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	538,134	843,134
Retained Earnings	612,919	511,382
Accumulated Other Comprehensive Loss	(3,123)	(3,922)
Common Stockholder's Equity	1,147,930	1,350,594
Total Liabilities and Capitalization	$ 4,056,522	$ 4,062,661

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenues	$ 2,271,425	$ 1,988,512	$ 6,413,243	$ 5,856,458
Operating Expenses:
Purchased Power, Fuel and Transmission	842,291	651,776	2,442,953	1,955,129
Operations and Maintenance	344,475	307,773	970,881	956,274
Depreciation	208,671	194,466	612,077	571,152
Amortization of Regulatory Assets/(Liabilities), Net	92,711	41,848	174,108	58,058
Energy Efficiency Programs	129,965	129,205	366,162	391,761
Taxes Other Than Income Taxes	187,291	168,193	547,155	479,648
Total Operating Expenses	1,805,404	1,493,261	5,113,336	4,412,022
Operating Income/(Loss)	466,021	495,251	1,299,907	1,444,436
Interest Expense	125,201	108,719	372,734	319,477
Other Income, Net	16,718	28,536	100,656	79,178
Income Before Income Tax Expense	357,538	415,068	1,027,829	1,204,137
Income Tax Expense	66,278	152,818	220,497	447,921
Net Income	291,260	262,250	807,332	756,216
Net Income Attributable to Noncontrolling Interests	1,880	1,880	5,639	5,639
Net Income Attributable to Common Shareholders	$ 289,380	$ 260,370	$ 801,693	$ 750,577
Basic Earnings Per Common Share (in dollars per share)	$ 0.91	$ 0.82	$ 2.53	$ 2.36
Diluted Earnings Per Common Share	0.91	0.82	2.52	2.36
Dividends Declared Per Common Share (in dollars per share)	$ 0.51	$ 0.48	$ 1.52	$ 1.43
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,360,110	317,393,029	317,367,252	317,415,848
Diluted (in shares)	317,967,311	317,949,396	317,948,498	318,007,042
The Connecticut Light and Power Company
Operating Revenues	$ 865,028	$ 774,762	$ 2,344,903	$ 2,173,629
Operating Expenses:
Purchased Power, Fuel and Transmission	314,571	259,005	850,794	711,154
Operations and Maintenance	128,523	123,511	355,500	361,166
Depreciation	72,017	63,727	208,899	184,275
Amortization of Regulatory Assets, Net	54,031	34,574	97,437	58,799
Energy Efficiency Programs	30,240	37,739	71,606	106,483
Taxes Other Than Income Taxes	92,987	79,067	267,662	223,482
Total Operating Expenses	692,369	597,623	1,851,898	1,645,359
Operating Income/(Loss)	172,659	177,139	493,005	528,270
Interest Expense	37,609	36,313	113,107	106,577
Other Income, Net	7,098	7,913	20,722	15,402
Income Before Income Tax Expense	142,148	148,739	400,620	437,095
Income Tax Expense	41,818	52,595	102,010	159,450
Net Income	100,330	96,144	298,610	277,645
NSTAR Electric Company
Operating Revenues	939,460	851,922	2,400,324	2,290,432
Operating Expenses:
Purchased Power, Fuel and Transmission	383,208	294,115	981,895	799,007
Operations and Maintenance	123,634	118,777	344,478	346,469
Depreciation	70,616	68,746	205,210	204,442
Amortization of Regulatory Assets, Net	17,149	10,131	35,467	17,243
Energy Efficiency Programs	89,430	82,611	229,408	228,543
Taxes Other Than Income Taxes	49,927	47,830	145,740	130,492
Total Operating Expenses	733,964	622,210	1,942,198	1,726,196
Operating Income/(Loss)	205,496	229,712	458,126	564,236
Interest Expense	26,958	30,810	80,780	88,715
Other Income, Net	13,697	9,165	40,567	24,610
Income Before Income Tax Expense	192,235	208,067	417,913	500,131
Income Tax Expense	51,640	82,301	112,247	196,001
Net Income	140,595	125,766	305,666	304,130
Public Service Company of New Hampshire
Operating Revenues	290,203	250,032	792,700	733,572
Operating Expenses:
Purchased Power, Fuel and Transmission	100,763	57,099	293,975	179,289
Operations and Maintenance	55,429	65,104	153,296	195,637
Depreciation	23,223	32,084	69,524	95,266
Amortization of Regulatory Assets/(Liabilities), Net	27,357	2,835	41,318	(10,658)
Energy Efficiency Programs	5,863	4,007	15,694	11,040
Taxes Other Than Income Taxes	21,095	22,936	59,775	66,935
Total Operating Expenses	233,730	184,065	633,582	537,509
Operating Income/(Loss)	56,473	65,967	159,118	196,063
Interest Expense	16,593	12,896	43,977	38,676
Other Income, Net	16,095	2,664	24,253	7,367
Income Before Income Tax Expense	55,975	55,735	139,394	164,754
Income Tax Expense	15,309	22,012	37,857	65,128
Net Income	$ 40,666	$ 33,723	$ 101,537	$ 99,626

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net Income	$ 291,260	$ 262,250	$ 807,332	$ 756,216
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	432	519	1,627	1,567
Changes in Unrealized (Losses)/Gains on Marketable Securities	(136)	(1,872)	(724)	733
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	1,110	673	5,918	(633)
Net OCI	1,406	(680)	6,821	1,667
Comprehensive Income Attributable to Noncontrolling Interests	(1,880)	(1,880)	(5,639)	(5,639)
Comprehensive Income Attributable to Common Shareholders	290,786	259,690	808,514	752,244
The Connecticut Light and Power Company
Net Income	100,330	96,144	298,610	277,645
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	(7)	96	58	298
Changes in Unrealized (Losses)/Gains on Marketable Securities	(5)	(64)	(21)	25
Net OCI	(12)	32	37	323
Comprehensive Income Attributable to Common Shareholders	100,318	96,176	298,647	277,968
NSTAR Electric Company
Net Income	140,595	125,766	305,666	304,130
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	110	109	328	328
Changes in Unrealized (Losses)/Gains on Marketable Securities	(1)	(18)	(6)	7
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	1	(4)	3	(12)
Net OCI	110	87	325	323
Comprehensive Income Attributable to Common Shareholders	140,705	125,853	305,991	304,453
Public Service Company of New Hampshire
Net Income	40,666	33,723	101,537	99,626
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	268	291	835	872
Changes in Unrealized (Losses)/Gains on Marketable Securities	(7)	(112)	(36)	43
Net OCI	261	179	799	915
Comprehensive Income Attributable to Common Shareholders	$ 40,927	$ 33,902	$ 102,336	$ 100,541

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities:
Net Income	$ 807,332	$ 756,216
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	612,077	571,152
Deferred Income Taxes	70,402	374,863
Uncollectible Expense	50,720	30,111
Pension, SERP and PBOP Expense, Net	5,192	16,891
Pension and PBOP Contributions	(188,874)	(197,900)
Regulatory Overrecoveries, Net	189,932	185,952
Amortization of Regulatory Assets/(Liabilities), Net	174,108	58,058
Other	(129,039)	(197,876)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(212,326)	(107,473)
Fuel, Materials, Supplies and Inventory	44,702	23,686
Taxes Receivable/Accrued, Net	70,885	88,856
Accounts Payable	(72,591)	(96,551)
Other Current Assets and Liabilities, Net	(14,858)	(30,138)
Net Cash Flows Provided by Operating Activities	1,407,662	1,475,847
Investing Activities:
Investments in Property, Plant and Equipment	(1,885,081)	(1,642,280)
Proceeds from Sales of Marketable Securities	405,276	520,664
Purchases of Marketable Securities	(396,277)	(506,302)
Proceeds from the Sale of Generation Assets	193,924	0
Other Investing Activities	(23,405)	(24,173)
Net Cash Flows Used in Investing Activities	(1,705,563)	(1,652,091)
Financing Activities:
Cash Dividends on Common Stock	(480,082)	(451,562)
Cash Dividends on Preferred Stock	(5,639)	(5,639)
Increase/(Decrease) in Notes Payable	(222,110)	(231,500)
Issuance of Rate Reduction Bonds	635,663	0
Issuance of Long-Term Debt	1,300,000	1,250,000
Retirement of Long-Term Debt	(860,855)	(320,000)
Other Financing Activities	(20,361)	171
Net Cash Flows (Used in)/Provided by Financing Activities	346,616	241,470
Net Increase in Cash, Cash Equivalents and Restricted Cash	48,715	65,226
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	85,890	106,750
Cash, Cash Equivalents and Restricted Cash - End of Period	134,605	171,976
The Connecticut Light and Power Company
Operating Activities:
Net Income	298,610	277,645
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	208,899	184,275
Deferred Income Taxes	28,637	90,132
Uncollectible Expense	12,135	1,755
Pension, SERP and PBOP Expense, Net	6,594	6,421
Pension Contributions	(41,150)	(1,875)
Regulatory Overrecoveries, Net	(1,136)	71,413
Amortization of Regulatory Assets, Net	97,437	58,799
Other	(55,827)	(23,911)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(126,513)	(70,936)
Taxes Receivable/Accrued, Net	72,702	69,335
Accounts Payable	(15,303)	(1,649)
Other Current Assets and Liabilities, Net	(33,965)	(36,340)
Net Cash Flows Provided by Operating Activities	451,120	625,064
Investing Activities:
Investments in Property, Plant and Equipment	(660,673)	(621,882)
Other Investing Activities	167	185
Net Cash Flows Used in Investing Activities	(660,506)	(621,697)
Financing Activities:
Cash Dividends on Common Stock	(60,000)	(205,200)
Cash Dividends on Preferred Stock	(4,169)	(4,169)
Capital Contributions from Eversource Parent	100,000	0
(Decrease)/Increase in Notes Payable to Eversource Parent	(23,600)	(80,100)
Premium on Issuance of Long-Term Debt	0	21,937
Issuance of Long-Term Debt	500,000	525,000
Retirement of Long-Term Debt	(300,000)	(250,000)
Other Financing Activities	(7,584)	(6,322)
Net Cash Flows (Used in)/Provided by Financing Activities	204,647	1,146
Net Increase in Cash, Cash Equivalents and Restricted Cash	(4,739)	4,513
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	9,619	8,403
Cash, Cash Equivalents and Restricted Cash - End of Period	4,880	12,916
NSTAR Electric Company
Operating Activities:
Net Income	305,666	304,130
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	205,210	204,442
Deferred Income Taxes	16,203	100,335
Uncollectible Expense	20,433	14,937
Pension, SERP and PBOP Income, Net	(15,855)	(7,586)
Pension and PBOP Contributions	(60,454)	(83,040)
Regulatory Overrecoveries, Net	180,797	71,647
Amortization of Regulatory Assets, Net	35,467	17,243
Other	(49,178)	(47,972)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(155,669)	(113,960)
Fuel, Materials, Supplies and Inventory	29,156	11,483
Taxes Receivable/Accrued, Net	42,148	71,705
Accounts Payable	(13,178)	(42,519)
Other Current Assets and Liabilities, Net	33,543	4,982
Net Cash Flows Provided by Operating Activities	574,289	505,827
Investing Activities:
Investments in Property, Plant and Equipment	(538,973)	(467,275)
Other Investing Activities	46	(3,565)
Net Cash Flows Used in Investing Activities	(538,927)	(470,840)
Financing Activities:
Cash Dividends on Common Stock	(161,000)	(214,500)
Cash Dividends on Preferred Stock	(1,470)	(1,470)
Capital Contributions from Eversource Parent	105,500	2,300
Increase in Notes Payable to Eversource Parent	16,000	0
Increase/(Decrease) in Notes Payable	6,500	(80,600)
Issuance of Long-Term Debt	0	350,000
Other Financing Activities	(239)	(3,410)
Net Cash Flows (Used in)/Provided by Financing Activities	(34,709)	52,320
Net Increase in Cash, Cash Equivalents and Restricted Cash	653	87,307
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	14,708	15,506
Cash, Cash Equivalents and Restricted Cash - End of Period	15,361	102,813
Public Service Company of New Hampshire
Operating Activities:
Net Income	101,537	99,626
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	69,524	95,266
Deferred Income Taxes	11,473	43,217
Uncollectible Expense	4,900	5,200
Regulatory Overrecoveries, Net	(19,764)	8,910
Amortization of Regulatory Assets/(Liabilities), Net	41,318	(10,658)
Other	(3,104)	(7,866)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(32,819)	(30,276)
Fuel, Materials, Supplies and Inventory	14,555	4,263
Taxes Receivable/Accrued, Net	10,929	10,749
Accounts Payable	(3,828)	18,394
Other Current Assets and Liabilities, Net	27,844	32,300
Net Cash Flows Provided by Operating Activities	217,665	263,925
Investing Activities:
Investments in Property, Plant and Equipment	(236,206)	(215,470)
Proceeds from the Sale of Generation Assets	193,924	0
Proceeds from the Sale of Property	4,782	0
Other Investing Activities	367	113
Net Cash Flows Used in Investing Activities	(37,133)	(215,357)
Financing Activities:
Cash Dividends on Common Stock	(150,000)	(23,900)
Capital Contributions from Eversource Parent	225,000	0
Return of Capital	(530,000)	0
(Decrease)/Increase in Notes Payable to Eversource Parent	(216,300)	41,400
Issuance of Rate Reduction Bonds	635,663	0
Retirement of Long-Term Debt	(110,000)	(70,000)
Other Financing Activities	1,080	(187)
Net Cash Flows (Used in)/Provided by Financing Activities	(144,557)	(52,687)
Net Increase in Cash, Cash Equivalents and Restricted Cash	35,975	(4,119)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	2,191	5,953
Cash, Cash Equivalents and Restricted Cash - End of Period	$ 38,166	$ 1,834

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017 , the results of operations and comprehensive income for the three and nine months ended September 30, 2018 and 2017 , and the cash flows for the nine months ended September 30, 2018 and 2017 . The results of operations and comprehensive income for the three and nine months ended September 30, 2018 and 2017 and the cash flows for the nine months ended September 30, 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 and transmission businesses, and water distribution business, 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. B. Accounting Standards Accounting Standards Issued but Not Yet Effective: In February 2016, the FASB issued Accounting Standards Update ("ASU") 2016-02, Leases (Topic 842) , which changes existing lease accounting guidance and is required to be applied in the first quarter of 2019, with earlier application permitted. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) - Targeted Improvements , allowing a transition method to adopt the new leases standard as of the adoption date and recognizing a cumulative-effect to the opening balance of retained earnings in the period of adoption, with comparative periods presented in the financial statements continuing to follow existing lease accounting guidance under Topic 840 (Leases) in the accounting literature. The Company intends to adopt the transition method allowed in ASU 2018-11. The Company will implement the new leases standard in the first quarter of 2019 and apply the Topic 842 lease criteria to new leases and lease renewals entered into effective on or after January 1, 2019. The requirements of the new leases standard 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, including the practical expedients, will have on its financial statements, including reviewing its lease population. The Company has decided to elect the practical expedient package whereby it need not reassess whether a contract is or contains a lease or whether a lease is an operating or capital lease and it need not reassess initial direct costs for leases. 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 16, "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 $0.4 million and $22.4 million , respectively, for the three and nine months ended September 30, 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. Unrealized gains recorded in Other Income, Net were $2.4 million and $2.6 million for the three and nine months ended September 30, 2018 , respectively. 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, SERP 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 September 30, 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 $30 million , as these amounts continue to be included in rates. See Note 1G, "Summary of Significant Accounting Policies - Other Income, Net," to the financial statements for the portion of pension, SERP and PBOP costs that are presented as non-operating income for the three and nine months ended September 30, 2018 and 2017 . For the three months ended September 30, 2017, the amounts, which were previously presented within Operations and Maintenance expense on the statements of income, totaled $7.3 million at Eversource, $0.4 million at CL&P, $4.7 million at NSTAR Electric and $1.5 million at PSNH, and have been retrospectively presented within Other Income, Net. For the nine months ended September 30, 2017, these amounts were $22.9 million at Eversource, $1.3 million at CL&P, $14.5 million at NSTAR Electric and $4.5 million at PSNH. 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 $16.4 million and $14.0 million for the nine months ended September 30, 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 1I, "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 September 30, 2018 , our capitalized Northern Pass project costs were approximately $302 million . In March 2018, the New Hampshire Site Evaluation Committee ("NHSEC") issued a written decision denying Northern Pass’ siting application and the Massachusetts EDCs terminated the selection of, and subsequent contract negotiations with, Northern Pass under the Massachusetts Clean Energy RFP. On April 27, 2018, NPT filed a motion for rehearing with the NHSEC and on July 12, 2018, the NHSEC issued its written decision denying Northern Pass’ motion for rehearing. On August 10, 2018, NPT filed an appeal to the New Hampshire Supreme Court, based on the NHSEC’s failure to follow applicable law in its review of the project. On October 12, 2018, the New Hampshire Supreme Court accepted this appeal and directed the NHSEC to transmit the record of its proceedings to the Court by December 11, 2018. The Supreme Court has not yet issued a schedule for the balance of the appeal process. In parallel, NPT intends to continue to pursue all available options to secure NHSEC approval and to construct the project. The March 2018 NHSEC denial of Northern Pass' siting application caused us to review the recoverability of our Northern Pass project costs in the first quarter of 2018. 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 was recoverable. Our undiscounted cash flows were substantially in excess of our estimated project costs. We completed this analysis and concluded that our project costs were recoverable as of March 31, 2018, based on our expectation that the Northern Pass project remains probable of being placed in service. The events that occurred subsequent to March 31, 2018 did not require an additional review of the recoverability of the Northern Pass project costs as of September 30, 2018. 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 $302 million of capitalized project costs being impaired. Such an impairment could have a material adverse effect on our financial position and results of operations. D. Impairment of Access Northeast Access Northeast is a natural gas pipeline and storage project being developed jointly by Eversource, Enbridge, Inc. ("Enbridge") and National Grid plc ("National Grid"), through Algonquin Gas Transmission, LLC ("AGT"). Eversource's investments include a 40 percent ownership interest in Access Northeast, which is accounted for as an equity method investment. Equity method investments are assessed for impairment when conditions exist that indicate that the fair value of the investment is less than book value. If the decline in value is considered to be other-than-temporary, the investment is written down to its estimated fair value, which establishes a new cost basis in the investment. Impairment evaluations involve a significant degree of judgment and estimation, including identifying circumstances that indicate an impairment may exist and developing undiscounted future cash flows. In 2015 and 2016, AGT sought to secure long-term natural gas pipeline capacity contracts with EDCs in Massachusetts, Connecticut, New Hampshire, Maine, and Rhode Island. Subsequently, in 2016, the Massachusetts Supreme Judicial Court and the NHPUC each ruled that state statutes precluded the state regulatory agencies from approving those contracts in Massachusetts and New Hampshire, respectively. The New Hampshire Supreme Court overruled the NHPUC decision in May 2018. Legislative changes are needed in Massachusetts to allow the DPU to approve natural gas pipeline capacity contracts. No such changes have occurred during any legislative session in 2017 or 2018. In September 2018, certain non-Eversource natural gas related events in eastern Massachusetts resulted in widespread property and system damage, personal injuries, and a fatality. As a result of these events, compounded by the failure to secure Massachusetts legislation to date, we believe there is significant uncertainty around the future timing of, and ability to secure, needed legislative change affecting the natural gas industry and pipeline expansion, which may significantly delay the completion of the Access Northeast project. Eversource identified the September 2018 natural gas related event, compounded by the adverse legislative environment, as negative evidence that indicated potential impairment. Our impairment assessment uses a discounted cash flow income approach, including consideration of the severity and duration of any decline in fair value of our investment in the project, and involves significant management judgment and estimation, including projections of the project’s discounted cash flows and assumptions about exit price. As of September 30, 2018, management determined that the future cash flows of the Access Northeast project are uncertain and can no longer be reasonably estimated and that the book value of our equity method investment is not recoverable. As a result, for the three months ended September 30, 2018, Eversource recorded an other-than-temporary impairment of $32.9 million within Other Income, Net on our statement of income, representing the full carrying value of our equity method investment. E. 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 September 30, 2018 As of December 31, 2017 As of September 30, 2018 As of December 31, 2017 Eversource $ 218.1 $ 195.7 $ 132.6 $ 122.5 CL&P 84.6 78.9 68.3 65.5 NSTAR Electric 82.0 69.7 46.5 40.3 PSNH 11.3 10.5 — — In accordance with new revenue accounting guidance, uncollectible expense associated with customers' accounts receivable included in Operations and Maintenance expense on the statements of income is as follows: For the Three Months Ended For the Nine Months Ended (Millions of Dollars) September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 Eversource $ 21.5 $ 14.4 $ 50.7 $ 30.1 CL&P 4.4 3.6 12.1 1.8 NSTAR Electric 9.1 8.1 20.4 14.9 PSNH 1.6 1.5 4.9 5.2 F. 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, long-term debt and RRBs. 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 11, "Fair Value of Financial Instruments," to the financial statements. G. Other Income, Net The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended September 30, 2018 September 30, 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) $ 14.8 $ 2.0 $ 9.0 $ 2.0 $ 7.3 $ 0.4 $ 4.7 $ 1.5 AFUDC Equity 12.0 3.3 4.2 — 9.2 3.3 2.7 — Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates (2) (27.9 ) — 0.2 — 5.1 — 0.3 — Investment Income/(Loss) 1.8 0.7 (0.4 ) 0.1 4.6 3.1 0.9 0.7 Interest Income (3) 10.8 0.9 0.2 9.6 2.3 1.1 0.6 0.5 Gain on Sale of Property 5.0 — 0.5 4.4 — — — — Other 0.2 0.2 — — — — — — Total Other Income, Net (1) $ 16.7 $ 7.1 $ 13.7 $ 16.1 $ 28.5 $ 7.9 $ 9.2 $ 2.7 For the Nine Months Ended September 30, 2018 September 30, 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) $ 44.6 $ 7.3 $ 26.8 $ 6.4 $ 22.9 $ 1.3 $ 14.5 $ 4.5 AFUDC Equity 32.6 9.4 11.5 — 23.8 8.2 6.7 — Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates (2) (0.4 ) — 0.6 — 23.0 — 0.2 — Investment Income 2.2 0.9 0.6 0.2 3.7 2.4 2.1 1.2 Interest Income (3) 16.2 2.9 0.6 13.3 5.8 3.5 1.1 1.6 Gain on Sale of Property 5.0 — 0.5 4.4 — — — — Other 0.5 0.2 — — — — — 0.1 Total Other Income, Net (1) $ 100.7 $ 20.7 $ 40.6 $ 24.3 $ 79.2 $ 15.4 $ 24.6 $ 7.4 (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 within Other Income, Net for the three and nine months ended September 30, 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. (2) For the three months ended September 30, 2018 , equity in earnings/(loss) and impairment of unconsolidated affiliates includes an other-than-temporary impairment of $32.9 million in the Access Northeast project investment. See Note 1D, "Summary of Significant Accounting Policies - Impairment of Access Northeast," for further information. For the nine months ended September 30, 2018 and 2017, equity in earnings includes $17.6 million and $9.7 million of unrealized gains associated with an investment in a renewable energy fund, respectively. (3) See Note 2, "Regulatory Accounting," for interest income recognized in the third quarter of 2018 for the equity return component of carrying charges on storm costs at PSNH. H. 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 For the Nine Months Ended (Millions of Dollars) September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 Eversource $ 43.5 $ 40.3 $ 122.5 $ 118.2 CL&P 40.6 37.8 107.7 103.5 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. Separate from the amounts above are $ 10.7 million and $36.1 million of amounts recorded as Taxes Other than Income Taxes for the three and nine months ended September 30, 2018 , respectively, related to the future remittance to the State of Connecticut of energy efficiency funds collected from customers in Operating Revenues. 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. I. Supplemental Cash Flow Information Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of September 30, 2018 As of September 30, 2017 Eversource $ 303.7 $ 307.7 CL&P 103.0 113.4 NSTAR Electric 62.5 92.5 PSNH 48.3 39.6 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 September 30, 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 $ 59.1 $ 1.0 $ 2.4 $ 7.5 $ 38.2 $ 6.0 $ 1.8 $ 0.9 Restricted cash included in: Prepayments and Other Current Assets 51.4 3.5 12.9 26.8 24.4 3.1 12.8 0.5 Marketable Securities 20.9 0.4 0.1 0.7 23.3 0.5 0.1 0.8 Other Long-Term Assets 3.2 — — 3.2 — — — — Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows $ 134.6 $ 4.9 $ 15.4 $ 38.2 $ 85.9 $ 9.6 $ 14.7 $ 2.2 Restricted cash included in Prepayments and Other Current Assets and Other Long-Term Assets, shown above, primarily represents required ISO-NE cash deposits and cash collections related to the PSNH RRB customer charges that are held in trust. 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. As a result of implementing new accounting guidance for the statement of cash flows, the reclassification of the change in restricted cash balances, which was previously classified as operating activities, resulted in a decrease of $30.2 million in the total cash and restricted cash change for the nine months ended September 30, 2017. J. Income Taxes On December 22, 2017, the Tax Cuts and Jobs Act became law, which amended existing federal tax rules to reduce U.S. federal corporate income tax rate from 35 percent to 21 percent effective January 1, 2018. Our regulated companies have established a liability 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 for the three and nine months ended September 30, 2018 . See Note 16, "Revenues," for further information on the amounts deducted from revenues. Eversource's annual return to provision process in the third quarter of 2018 resulted in significant benefits as a result of both tax reform and changes in Connecticut state tax legislation that resulted in the remeasurement of a tax reserve. These benefits from both federal tax reform and Connecticut tax law change reduced income tax expense by an aggregate $18 million for the three months ended September 30, 2018 .

REGULATORY ACCOUNTING

REGULATORY ACCOUNTING	9 Months Ended
	Sep. 30, 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: As of September 30, 2018 As of December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Benefit Costs $ 1,988.4 $ 447.4 $ 541.2 $ 172.0 $ 2,068.8 $ 469.2 $ 560.7 $ 212.3 Income Taxes, Net 720.7 448.1 112.9 15.6 768.9 453.8 113.2 21.7 Securitized Stranded Costs 618.6 — — 618.6 — — — — Deferred Costs from Generation Asset Sale — — — — 516.1 — — 516.1 Storm Restoration Costs, Net 598.5 319.7 222.1 56.7 404.8 216.7 146.6 41.5 Regulatory Tracker Mechanisms 257.8 39.5 128.4 74.9 509.9 85.3 273.0 116.4 Derivative Liabilities 360.0 359.9 — — 367.2 362.3 — — Goodwill-related 352.6 — 302.7 — 365.2 — 313.6 — Asset Retirement Obligations 87.5 31.8 41.3 3.3 101.0 30.3 39.0 17.0 Other Regulatory Assets 169.2 27.4 71.7 12.4 137.4 27.6 78.4 15.8 Total Regulatory Assets 5,153.3 1,673.8 1,420.3 953.5 5,239.3 1,645.2 1,524.5 940.8 Less: Current Portion 436.7 128.8 193.5 61.4 741.9 200.3 333.9 130.1 Total Long-Term Regulatory Assets $ 4,716.6 $ 1,545.0 $ 1,226.8 $ 892.1 $ 4,497.4 $ 1,444.9 $ 1,190.6 $ 810.7 Securitized Stranded Costs: On May 8, 2018, a subsidiary of PSNH issued $635.7 million of securitized RRBs to finance PSNH's unrecovered stranded costs associated with the divestiture of its generation assets. Securitized regulatory assets, which are not earning an equity return, are being recovered over the amortization period of the associated RRBs. The PSNH RRBs are expected to be repaid by February 1, 2033. The stranded costs related to the difference between the carrying value and the fair value less costs to sell the thermal generation assets were reflected as a deferred cost in the table above as of December 31, 2017, and are reflected in the securitized stranded costs balance as of September 30, 2018 . Storm Restoration Costs, Net: 2018 Storms: In 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 for deferral and recovery with the criteria specific to each state jurisdiction and utility company. Once a storm qualifies for recovery, all qualifying expenses incurred during storm restoration efforts are deferred and recovered from customers. Costs for storms that do not meet the specific criteria are expensed as incurred. The 2018 storms resulted in deferred storm restoration costs of approximately $266 million ( $149 million for CL&P, $101 million for NSTAR Electric, and $16 million for PSNH), which were reflected in Storm Restoration Costs, Net in the table above as of September 30, 2018 . 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 processes. On September 17, 2018, the NHPUC approved the recovery of $49 million , plus carrying charges, in storm costs incurred from August 2011 through March 2013 and the transfer of funding from PSNH’s major storm funding reserve to offset those costs. The costs of these storms (excluding the equity return component of the carrying charges) were deferred as regulatory assets, and the funding reserve collected from customers was accrued as a regulatory liability. The storm cost deferral is separate from the major storm funding reserve that is being collected from customers. As a result of the approval, PSNH recognized $8.7 million (pre-tax) within Other Income, Net on our statement of income in the third quarter of 2018 for the equity return component of the carrying charges, which have been billed and collected. Storm costs incurred from March 2013 through 2016 are currently being audited by the NHPUC staff. Regulatory Costs in Long-Term Assets: Eversource's regulated companies had $104.6 million (including $27.6 million for CL&P, $53.3 million for NSTAR Electric and $3.9 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 September 30, 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. Regulatory Liabilities: The components of regulatory liabilities were as follows: As of September 30, 2018 As of December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Excess ADIT due to Tax Cuts and Jobs Act $ 2,876.9 $ 1,026.3 $ 1,100.5 $ 397.4 $ 2,882.0 $ 1,031.6 $ 1,087.9 $ 405.1 Cost of Removal 516.4 37.8 305.7 24.9 502.1 23.2 293.8 37.9 Benefit Costs 127.1 — 107.2 0.5 132.3 — 112.6 — Regulatory Tracker Mechanisms 345.6 111.9 168.3 38.5 136.7 34.6 77.8 5.0 AFUDC - Transmission 68.6 47.8 20.8 — 67.1 48.8 18.3 — Revenue Subject to Refund 36.2 8.3 3.7 9.4 — — — — Other Regulatory Liabilities 80.7 25.7 28.3 2.8 45.2 12.9 3.7 2.7 Total Regulatory Liabilities 4,051.5 1,257.8 1,734.5 473.5 3,765.4 1,151.1 1,594.1 450.7 Less: Current Portion 344.7 126.6 168.2 39.7 128.1 39.0 79.6 6.3 Total Long-Term Regulatory Liabilities $ 3,706.8 $ 1,131.2 $ 1,566.3 $ 433.8 $ 3,637.3 $ 1,112.1 $ 1,514.5 $ 444.4 Revenue Subject to Refund: The regulatory liability balance represents 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 for NSTAR Electric, May 1, 2018 for CL&P and July 1, 2018 for NSTAR Gas, base rates charged to customers have been adjusted to reflect the new federal income tax rate. As part of CL&P's 2018 rate case settlement, a new capital tracker regulatory mechanism was established, which includes the refund of the reserve for the higher federal corporate income tax rate to customers between January 1, 2018 through April 30, 2018 in rates, from July 1, 2018 through December 31, 2018.

PROPERTY, PLANT AND EQUIPMENT A

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	9 Months Ended
	Sep. 30, 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 September 30, 2018 As of December 31, 2017 (Millions of Dollars) Distribution - Electric $ 14,794.9 $ 14,410.5 Distribution - Natural Gas 3,371.2 3,244.2 Transmission - Electric 9,733.6 9,270.9 Distribution - Water 1,594.3 1,558.4 Solar 109.3 36.2 Utility 29,603.3 28,520.2 Other (1) 759.0 693.7 Property, Plant and Equipment, Gross 30,362.3 29,213.9 Less: Accumulated Depreciation Utility (7,065.4 ) (6,846.9 ) Other (325.4 ) (286.9 ) Total Accumulated Depreciation (7,390.8 ) (7,133.8 ) Property, Plant and Equipment, Net 22,971.5 22,080.1 Construction Work in Progress 1,996.2 1,537.4 Total Property, Plant and Equipment, Net $ 24,967.7 $ 23,617.5 As of September 30, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution $ 6,027.1 $ 6,651.1 $ 2,157.0 $ 5,888.3 $ 6,479.0 $ 2,083.4 Transmission 4,513.7 3,915.5 1,255.6 4,239.9 3,821.2 1,161.3 Solar — 109.3 — — 36.2 — Property, Plant and Equipment, Gross 10,540.8 10,675.9 3,412.6 10,128.2 10,336.4 3,244.7 Less: Accumulated Depreciation (2,297.4 ) (2,673.0 ) (762.1 ) (2,239.0 ) (2,550.2 ) (751.8 ) Property, Plant and Equipment, Net 8,243.4 8,002.9 2,650.5 7,889.2 7,786.2 2,492.9 Construction Work in Progress 510.3 573.2 176.0 381.8 460.3 149.4 Total Property, Plant and Equipment, Net $ 8,753.7 $ 8,576.1 $ 2,826.5 $ 8,271.0 $ 8,246.5 $ 2,642.3 (1) These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	9 Months Ended
	Sep. 30, 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 September 30, 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: Eversource Level 2 $ 0.8 $ (0.5 ) $ 0.3 $ — $ — $ — CL&P Level 3 8.8 (4.8 ) 4.0 9.5 (7.1 ) 2.4 Long-Term Derivative Assets: CL&P Level 3 75.0 (2.3 ) 72.7 71.9 (5.3 ) 66.6 Current Derivative Liabilities: Eversource Level 2 — — — (4.5 ) — (4.5 ) CL&P Level 3 (50.8 ) — (50.8 ) (54.4 ) — (54.4 ) Long-Term Derivative Liabilities: Eversource Level 2 (0.1 ) — (0.1 ) (0.4 ) — (0.4 ) CL&P Level 3 (385.8 ) — (385.8 ) (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 1F, "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 September 30, 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 price of 10.6 million and 9.5 million MMBtu of natural gas, respectively. For the three months ended September 30, 2018 and 2017 , there were gains of $1.6 million and $0.6 million , respectively, deferred as regulatory costs, which reflect the change in fair value associated with Eversource's derivative contracts. For the nine months ended September 30, 2018 and 2017, there were losses of $25.8 million and $30.3 million , respectively. 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 September 30, 2018 As of December 31, 2017 CL&P Range Period Covered Range Period Covered Capacity Prices $ 4.30 — 7.44 per kW-Month 2022-2026 $ 5.00 — 8.70 per kW-Month 2021 - 2026 Forward Reserve $ 0.95 — 2.00 per kW-Month 2019-2024 $ 1.00 — 2.00 per kW-Month 2018 - 2024 Exit price premiums of 1 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, capacity or forward reserve 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 September 30, For the Nine Months Ended September 30, (Millions of Dollars) 2018 2017 2018 2017 Derivatives, Net: Fair Value as of Beginning of Period $ (369.3 ) $ (394.8 ) $ (362.3 ) $ (420.5 ) Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities 1.2 (0.7 ) (27.0 ) (15.9 ) Settlements 8.2 13.9 29.4 54.8 Fair Value as of End of Period $ (359.9 ) $ (381.6 ) $ (359.9 ) $ (381.6 )

MARKETABLE SECURITIES

MARKETABLE SECURITIES	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
MARKETABLE SECURITIES	MARKETABLE SECURITIES Eversource holds marketable securities that are primarily used to fund certain non-qualified executive benefits. The trusts that hold marketable securities 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 equity securities are recorded in Other Income, Net on the statements of income. The fair value of equity securities subject to this guidance as of September 30, 2018 and December 31, 2017 was $54.5 million and $50 million , respectively. For the three and nine months ended September 30, 2018 , there were unrealized gains of $2.4 million and $2.6 million , respectively, 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 $ 258.0 million and $ 263.8 million as of September 30, 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 September 30, 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 $ 292.8 $ 0.8 $ (2.7 ) $ 290.9 $ 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 $247.1 million and $242.3 million as of September 30, 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 and nine months ended September 30, 2018 and 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 September 30, 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) $ 28.5 $ 28.5 One to five years 48.7 48.3 Six to ten years 61.8 61.2 Greater than ten years 153.8 152.9 Total Debt Securities $ 292.8 $ 290.9 (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 September 30, 2018 As of December 31, 2017 Level 1: Mutual Funds and Equities $ 312.5 $ 313.8 Money Market Funds 20.9 23.3 Total Level 1 $ 333.4 $ 337.1 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 80.8 $ 70.2 Corporate Debt Securities 41.8 50.9 Asset-Backed Debt Securities 14.3 21.2 Municipal Bonds 121.2 110.7 Other Fixed Income Securities 11.9 10.7 Total Level 2 $ 270.0 $ 263.7 Total Marketable Securities $ 603.4 $ 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	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
SHORT-TERM AND LONG-TERM DEBT	SHORT-TERM AND LONG-TERM DEBT Short-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 September 30, 2018 or December 31, 2017 . Eversource's water distribution segment has a $100 million revolving credit facility, which expires on August 19, 2019, and there were no amounts outstanding as of September 30, 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 September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (Millions of Dollars) Eversource Parent Commercial Paper Program $ 826.7 $ 979.3 $ 623.3 $ 470.7 2.34 % 1.86 % NSTAR Electric Commercial Paper Program 240.5 234.0 409.5 416.0 2.17 % 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 September 30, 2018 , there were intercompany loans from Eversource parent of $45.9 million to CL&P, $46.6 million to PSNH and $16.0 million to Harbor Electric Energy Company, a wholly-owned subsidiary of NSTAR Electric ("HEEC"). Intercompany loans from Eversource parent to other Eversource subsidiaries primarily included $196.9 million to Eversource Service, $108.0 million to Aquarion, and $117.2 million to NSTAR Gas as of September 30, 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. We believe the future operating cash flows of Eversource, CL&P, NSTAR Electric and PSNH, along with our existing borrowing availability and access to financial markets for the issuance of new long-term debt, will be sufficient to meet any working capital and future operating requirements, and capital investment forecast opportunities. 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 for Issuances/ CL&P: 4.00% 2018 Series A First Mortgage Bonds March 2018 $ 500.0 April 2048 Repaid long-term debt that matured in 2018 and repaid short-term borrowings 5.65% 2008 Series A First Mortgage Bonds May 2008 (300.0 ) May 2018 Repaid at maturity on May 1, 2018 PSNH: 6.00% 2008 Series O First Mortgage Bonds May 2008 (110.0 ) May 2018 Repaid at maturity on May 1, 2018 Other: Eversource Parent 2.50% Series I Senior Notes (1) January 2018 200.0 March 2021 Repaid long-term debt that matured in 2018 and repaid short-term borrowings Eversource Parent 3.30% Series M Senior Notes January 2018 450.0 January 2028 Repaid long-term debt that matured in 2018 Eversource Parent 1.60% Series G Senior Notes January 2015 (150.0 ) January 2018 Repaid at maturity on January 15, 2018 Eversource Parent 1.45% Series E Senior Notes May 2013 (300.0 ) May 2018 Repaid at maturity on May 1, 2018 Yankee Gas 4.13% Series O First Mortgage Bonds September 2018 50.0 October 2048 Repaid long-term debt that matured in 2018 NSTAR Gas 4.09% Series P First Mortgage Bonds September 2018 100.0 October 2048 Repaid short-term borrowings Yankee Gas 6.90% Series J First Mortgage Bonds October 2018 (100.0 ) October 2018 Repaid at maturity on October 1, 2018 (1) 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 . On October 10, 2018, PSNH delivered a redemption notice for its $89.3 million adjustable rate 2001 Series A Pollution Control Revenue Bonds. The bonds, which are scheduled to mature on May 1, 2021, will be redeemed on November 28, 2018 at a redemption price of $89.3 million . The bonds are classified as Long-Term Debt on the balance sheet as of September 30, 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.

RATE REDUCTION BONDS AND VARIAB

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	9 Months Ended
	Sep. 30, 2018
Rate Reduction Bonds and Variable Interest Entity [Abstract]
RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES Rate Reduction Bonds: PSNH Funding LLC 3 (PSNH Funding) is a bankruptcy remote, special purpose, wholly-owned subsidiary of PSNH. PSNH Funding was formed solely to issue rate reduction bonds (RRBs) to finance PSNH’s unrecovered stranded costs associated with the divestiture of its generation assets. On May 8, 2018, PSNH Funding issued $635.7 million of securitized RRBs in multiple tranches with a weighted average interest rate of 3.66 percent , and final maturity dates ranging from 2026 to 2035. The RRBs are expected to be repaid by February 1, 2033. RRB payments consist of principal and interest and will be paid semi-annually, beginning on February 1, 2019. The RRBs were issued pursuant to a finance order issued by the NHPUC on January 30, 2018 to recover stranded costs resulting from the divestiture of PSNH’s generation assets. The proceeds were used to purchase PSNH’s stranded cost asset-recovery property, including its vested property right to bill, collect and adjust a non-bypassable stranded cost recovery charge from PSNH’s retail customers. The collections will be used to pay principal, interest and other costs in connection with the RRBs. The RRBs are secured by the stranded cost asset-recovery property. Cash collections from the stranded cost recovery charges and funds on deposit in trust accounts are the sole source of funds to satisfy the debt obligation. PSNH is not the owner of the RRBs, and PSNH Funding’s assets and revenues are not available to pay PSNH’s creditors. The RRBs are non-recourse senior secured obligations of PSNH Funding and are not insured or guaranteed by PSNH or Eversource Energy. PSNH Funding is considered a variable interest entity ( VIE) primarily because the equity capitalization is insufficient to support its operations. PSNH has the power to direct the significant activities of the VIE and is most closely associated with the VIE as compared to other interest holders. Therefore, PSNH is considered the primary beneficiary and consolidates PSNH Funding in its consolidated financial statements. The following tables summarize the impact of PSNH Funding on PSNH's balance sheet and income statement: (Millions of Dollars) Balance Sheet: As of September 30, 2018 Restricted Cash - Current Portion (included in Prepayments and Other Current Assets) $ 26.9 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 3.2 Securitized Stranded Cost (included in Regulatory Assets) 618.6 Other Regulatory Liabilities (included in Regulatory Liabilities) 1.0 Accrued Interest (included in Other Current Liabilities) 8.8 Rate Reduction Bonds - Current Portion 52.3 Rate Reduction Bonds - Long-Term Portion 583.3 (Millions of Dollars) Income Statement: For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2018 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 10.2 $ 17.1 Interest Expense on RRB Principal (included in Interest Expense) 6.0 8.8 Variable Interest Entities - Other: The Company's variable interests outside of the consolidated group include contracts that are required by regulation and provide for regulatory recovery of contract costs and benefits through customer rates. Eversource, CL&P and NSTAR Electric hold variable interests in VIEs through agreements with certain entities that own single renewable energy or peaking generation power plants, with other independent power producers and with transmission businesses. Eversource, CL&P and NSTAR Electric do not control the activities that are economically significant to these VIEs or provide financial or other support to these VIEs. Therefore, Eversource, CL&P and NSTAR Electric do not consolidate these VIEs.

PENSION BENEFITS AND POSTRETIRE

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION	9 Months Ended
	Sep. 30, 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 and deferred portion, as these amounts are cash settled on a short-term basis. Pension and SERP For the Three Months Ended September 30, 2018 For the Three Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 20.9 $ 5.2 $ 4.3 $ 2.7 $ 17.4 $ 4.6 $ 3.8 $ 2.4 Interest Cost 49.2 10.5 10.9 5.5 47.2 10.5 10.7 5.3 Expected Return on Plan Assets (97.8 ) (19.4 ) (26.6 ) (10.8 ) (83.5 ) (17.8 ) (21.9 ) (10.0 ) Actuarial Loss 35.7 7.1 10.1 3.3 33.9 6.8 10.4 3.0 Prior Service Cost 2.0 0.2 0.1 0.1 1.2 0.4 0.2 0.1 Total Net Periodic Benefit Expense/(Income) $ 10.0 $ 3.6 $ (1.2 ) $ 0.8 $ 16.2 $ 4.5 $ 3.2 $ 0.8 Intercompany Allocations N/A $ 1.5 $ 1.6 $ 0.5 N/A $ 2.4 $ 2.3 $ 0.8 Capitalized Pension Expense $ 6.6 $ 2.0 $ 1.8 $ 0.8 $ 5.5 $ 2.4 $ 2.0 $ 0.4 Pension and SERP For the Nine Months Ended September 30, 2018 For the Nine Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 64.2 $ 16.2 $ 13.1 $ 8.4 $ 53.8 $ 13.9 $ 11.7 $ 7.3 Interest Cost 147.1 31.4 32.6 16.4 140.7 31.3 31.9 15.9 Expected Return on Plan Assets (293.8 ) (59.7 ) (78.3 ) (32.6 ) (250.5 ) (53.9 ) (65.8 ) (29.9 ) Actuarial Loss 107.6 21.9 31.0 9.8 101.3 20.7 30.9 8.7 Prior Service Cost 6.0 0.8 0.2 0.2 3.4 1.1 0.4 0.4 Total Net Periodic Benefit Expense/(Income) $ 31.1 $ 10.6 $ (1.4 ) $ 2.2 $ 48.7 $ 13.1 $ 9.1 $ 2.4 Intercompany Allocations N/A $ 4.5 $ 4.8 $ 1.4 N/A $ 7.4 $ 6.9 $ 2.5 Capitalized Pension Expense $ 20.2 $ 6.2 $ 5.8 $ 2.3 $ 16.5 $ 7.3 $ 5.7 $ 1.1 PBOP For the Three Months Ended September 30, 2018 For the Three Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 2.5 $ 0.4 $ 0.5 $ 0.3 $ 2.4 $ 0.5 $ 0.4 $ 0.3 Interest Cost 7.7 1.5 2.2 0.9 6.8 1.3 2.2 0.8 Expected Return on Plan Assets (18.2 ) (2.6 ) (8.1 ) (1.5 ) (16.0 ) (2.4 ) (7.2 ) (1.4 ) Actuarial Loss 2.6 0.4 0.5 0.2 2.2 0.2 0.9 0.1 Prior Service Cost/(Credit) (6.0 ) 0.3 (4.3 ) 0.1 (5.3 ) 0.3 (4.3 ) 0.2 Total Net Periodic Benefit Income $ (11.4 ) $ — $ (9.2 ) $ — $ (9.9 ) $ (0.1 ) $ (8.0 ) $ — Intercompany Allocations N/A $ (0.3 ) $ (0.3 ) $ (0.1 ) N/A $ (0.2 ) $ (0.2 ) $ (0.1 ) Capitalized PBOP Expense/(Income) $ 0.7 $ 0.1 $ 0.2 $ 0.1 $ (4.8 ) $ (0.1 ) $ (4.1 ) $ — PBOP For the Nine Months Ended September 30, 2018 For the Nine Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 7.5 $ 1.4 $ 1.6 $ 0.9 $ 7.1 $ 1.5 $ 1.4 $ 1.0 Interest Cost 23.0 4.4 6.5 2.5 20.3 4.0 6.5 2.3 Expected Return on Plan Assets (54.2 ) (7.8 ) (24.4 ) (4.5 ) (47.8 ) (7.3 ) (21.6 ) (4.1 ) Actuarial Loss 7.7 1.2 1.7 0.6 6.9 0.7 2.6 0.4 Prior Service Cost/(Credit) (17.6 ) 0.8 (12.7 ) 0.4 (16.1 ) 0.8 (12.8 ) 0.4 Total Net Periodic Benefit Income $ (33.6 ) $ — $ (27.3 ) $ (0.1 ) $ (29.6 ) $ (0.3 ) $ (23.9 ) $ — Intercompany Allocations N/A $ (0.8 ) $ (1.0 ) $ (0.3 ) N/A $ (0.5 ) $ (0.8 ) $ (0.3 ) Capitalized PBOP Expense/(Income) $ 2.3 $ 0.5 $ 0.7 $ 0.3 $ (14.3 ) $ (0.4 ) $ (12.1 ) $ —

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 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 September 30, 2018 As of December 31, 2017 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 60 $ 66.6 59 $ 54.9 CL&P 14 5.0 14 4.7 NSTAR Electric 17 10.9 15 2.7 PSNH 9 5.5 10 5.7 The increase in the reserve balance was due primarily to the addition of an environmental site at NSTAR Electric and changes in cost estimates at certain MGP sites under investigation for which additional remediation will be required. 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 $52.3 million and $49.0 million as of September 30, 2018 and December 31, 2017 , respectively, and related primarily to the natural gas business segment. 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 required environmental remediation. 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 September 30, 2018 : Company Description Maximum Exposure (in millions) Expiration Dates On behalf of subsidiaries: Eversource Gas Transmission LLC Access Northeast Project Capital Contributions Guaranty (1) $ 184.9 2021 Various Surety Bonds (2) 42.7 2018 - 2019 Eversource Service and Rocky River Realty Company Lease Payments for Vehicles and Real Estate 6.6 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”). The DOE Phase IV trial is now expected to begin in early 2019. 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. A summary of the four separate complaints and the base ROEs pertinent to those complaints were 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 September 30, 2018 (in millions) First 10/1/2011 - 12/31/2012 11.14% 10.57% $— (2) Second 12/27/2012 - 3/26/2014 11.14% N/A 39.1 (3) Third 7/31/2014 - 10/30/2015 11.14% 10.57% — Fourth 4/29/2016 - 7/28/2017 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) All amounts associated with the first complaint period have been refunded, which totaled $38.9 million (pre-tax and excluding interest) at Eversource and reflected both the base ROE and incentive cap prescribed by the FERC order. The refund consisted of $22.4 million for CL&P, $13.7 million for NSTAR Electric and $2.8 million for PSNH. (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 September 30, 2018 . In response to appeals of the October 16, 2014 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. On October 16, 2018, FERC issued an order on all four complaints describing how it intends to address the issues that were remanded by the Court. FERC proposed a new framework to determine (1) whether an existing ROE is unjust and unreasonable and, if so, (2) how to calculate a replacement ROE. The parties to these proceedings were directed to submit briefs on this new proposed framework and how they would apply them in each of the four complaint proceedings. Briefs and reply briefs will be filed in the first quarter of 2019. The FERC order included illustrative calculations for the first complaint, using FERC's proposed frameworks with financial data from that complaint. Those preliminary calculations indicated that for the first complaint period, for the NETOs that FERC concludes are of average financial risk, (1) a preliminary range of presumptively just and reasonable base ROEs is 9.60 percent to 10.99 percent ; (2) the pre-existing base ROE of 11.14 percent is therefore unjust and unreasonable; (3) the preliminary just and reasonable base ROE is 10.41 percent ; and (4) the preliminary incentive cap on total ROE is 13.08 percent . If the results of these illustrative calculations were included in a final FERC order, then the 10.41 percent base ROE and a 13.08 percent incentive cap would not have a significant impact on our financial statements for the first complaint period. Although the order provided illustrative calculations, FERC stated that these calculations are merely preliminary. The FERC’s preliminary calculations are not binding and do not represent what we believe to be the most likely outcome of a final FERC order, as significant changes to the methodology by FERC are possible as a result of the parties’ arguments and calculations in the briefing process. Until FERC issues a final decision on each of these four complaints, there is significant uncertainty, and at this time, the Company cannot reasonably estimate a range of gain or loss for any of the four complaint proceedings. The October 16, 2018 FERC order does not provide a reasonable basis for a change to the 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. 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, 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 resulted in the initial $17.5 million of construction costs on the new cable being expensed as incurred, all of which were fully expensed by June 30, 2018. Construction of the new cable is underway and is expected to be completed in 2019.

ASSETS HELD FOR SALE

ASSETS HELD FOR SALE	9 Months Ended
	Sep. 30, 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, pursuant to which PSNH agreed to divest its generation assets, subject to NHPUC approval. The NHPUC approved this agreement as well as the final divestiture plan and auction process in the second half of 2016. On October 11, 2017, PSNH entered into two Purchase and Sale Agreements with private investors, one to sell its thermal generation assets at a purchase price of $175 million , subject to adjustment, (the “Thermal Agreement”) and a second to sell its hydroelectric generation assets at a purchase price of $83 million , subject to adjustment (the “Hydro Agreement”). The NHPUC approved these 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 Thermal Agreement. In accordance with the Thermal 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 . In the second quarter of 2018, the purchase price was further adjusted by $17.3 million relating to the valuation of certain allowances. As a result of these adjustments, net proceeds from the sale of the thermal assets totaled $116.8 million . On July 16, 2018, FERC issued its order approving the transfer of PSNH's six hydroelectric licenses to private investors. On August 26, 2018, PSNH completed the sale of its hydroelectric generation assets pursuant to the Hydro Agreement. In accordance with the Hydro Agreement, the original purchase price of $83 million was adjusted to reflect contractual adjustments totaling $5.7 million , resulting in net proceeds of $77.3 million . T he difference between the carrying value of the hydroelectric generation assets and the sale proceeds resulted in a gain of $17.2 million . An estimated gain from the sale of these assets was included as an offset to the total stranded costs associated with the sale of generation assets. On May 8, 2018, PSNH Funding issued $635.7 million of securitized RRBs to finance PSNH's unrecovered stranded costs associated with the divestiture of its generation assets, which included the d eferred costs resulting from the sale of the thermal generation assets. These bonds are secured by a non-bypassable charge billed to PSNH's customers. As of September 30, 2018, unamortized securitized stranded costs totaled $618.6 million and are included in Regulatory Assets on the Eversource and PSNH balance sheets. As of December 31, 2017, the deferred costs resulting from the thermal generation asset sale of $516.1 million represented the difference between the carrying value and the fair value less cost to sell the thermal generation assets. For further information on the securitized RRB issuance, see Note 7, "Rate Reduction Bonds and Variable Interest Entities." For the three and nine months ended September 30, 2018 , pre-tax income associated with the hydroelectric assets prior to the sale on August 26, 2018, was $0.7 million and $9.9 million , respectively. For the three and nine months ended September 30, 2017, pre-tax income associated with PSNH's generation assets was $14.6 million and $44.7 million , respectively. As of September 30, 2018 , all generation assets had been sold and as a result, no generation assets were classified as held for sale. As of December 31, 2017, PSNH's generation assets held for sale, which were included in current assets on the Eversource and PSNH balance sheets, and were part of the Electric Distribution reportable segment, were as follows: (Millions of Dollars) As of December 31, 2017 Thermal Gross Plant $ 1,091.4 Hydroelectric Gross Plant 83.0 Accumulated Depreciation (575.4 ) Net Plant 599.0 Fuel and Inventory 87.7 Materials and Supplies 27.3 Emissions Allowances 19.1 Other Assets 2.6 Deferred Costs from Thermal Generation Asset Sale (516.1 ) Total Generation Assets Held for Sale $ 219.6

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 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, Long-Term Debt and Rate Reduction Bonds: 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 and RRB 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 table below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of September 30, 2018: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 163.0 $ 116.2 $ 120.2 $ 43.0 $ 42.8 $ — $ — Long-Term Debt 12,538.8 12,517.4 3,253.6 3,420.4 2,944.6 2,990.0 894.1 904.3 Rate Reduction Bonds 635.7 631.3 — — — — 635.7 631.3 As of December 31, 2017: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 160.8 $ 116.2 $ 116.5 $ 43.0 $ 44.3 $ — $ — Long-Term Debt 12,325.5 12,877.1 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 1F, "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)	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30, 2018 For the Nine Months Ended September 30, 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 — (0.7 ) 2.6 1.9 — 0.7 (3.5 ) (2.8 ) Amounts Reclassified from AOCI 1.6 — 3.3 4.9 1.6 — 2.9 4.5 Net OCI 1.6 (0.7 ) 5.9 6.8 1.6 0.7 (0.6 ) 1.7 Balance as of End of Period $ (4.6 ) $ (0.7 ) $ (54.3 ) $ (59.6 ) $ (6.6 ) $ 1.1 $ (58.1 ) $ (63.6 ) 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 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 1G, "Summary of Significant Accounting Policies - Other Income, Net," and Note 8, "Pension Benefits and Postretirement Benefits Other Than Pension."

COMMON SHAREHOLDERS' EQUITY AND

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	9 Months Ended
	Sep. 30, 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 September 30, 2018 and Issued as of Par Value December 31, 2017 September 30, 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 September 30, 2018 and December 31, 2017 , there were 16,992,594 Eversource common shares held as treasury shares. As of both September 30, 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 September 30, 2018 and 2017 and $5.6 million for each of the nine months ended September 30, 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 September 30, 2018 and December 31, 2017 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to Eversource parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest.

COMMON SHARES

COMMON SHARES	9 Months Ended
	Sep. 30, 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 September 30, 2018 and Issued as of Par Value December 31, 2017 September 30, 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 September 30, 2018 and December 31, 2017 , there were 16,992,594 Eversource common shares held as treasury shares. As of both September 30, 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 September 30, 2018 and 2017 and $5.6 million for each of the nine months ended September 30, 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 September 30, 2018 and December 31, 2017 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to Eversource parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest.

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 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. The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 Net Income Attributable to Common Shareholders $ 289.4 $ 260.4 $ 801.7 $ 750.6 Weighted Average Common Shares Outstanding: Basic 317,360,110 317,393,029 317,367,252 317,415,848 Dilutive Effect 607,201 556,367 581,246 591,194 Diluted 317,967,311 317,949,396 317,948,498 318,007,042 Basic EPS $ 0.91 $ 0.82 $ 2.53 $ 2.36 Diluted EPS $ 0.91 $ 0.82 $ 2.52 $ 2.36

REVENUES

REVENUES	9 Months Ended
	Sep. 30, 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 September 30, 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 $ 1,111.7 $ 42.8 $ — $ 41.2 $ — $ — $ 1,195.7 Commercial 789.6 40.8 — 17.9 — (1.2 ) 847.1 Industrial 98.7 18.9 — 1.3 — (2.6 ) 116.3 Total Retail Tariff Sales Revenue 2,000.0 102.5 — 60.4 — (3.8 ) 2,159.1 Wholesale Transmission Revenue — — 364.5 — 11.7 (300.2 ) 76.0 Wholesale Market Sales Revenue 48.8 11.4 — 1.3 — — 61.5 Other Revenue from Contracts with Customers 20.2 (0.5 ) 3.1 1.9 212.9 (213.5 ) 24.1 Reserve for Revenue Subject to Refund 5.2 (3.5 ) — (1.3 ) — — 0.4 Total Revenue from Contracts with Customers 2,074.2 109.9 367.6 62.3 224.6 (517.5 ) 2,321.1 Alternative Revenue Programs (51.6 ) (1.5 ) (37.0 ) 1.1 — 33.8 (55.2 ) Other Revenue 4.8 0.6 — 0.1 — — 5.5 Total Operating Revenues $ 2,027.4 $ 109.0 $ 330.6 $ 63.5 $ 224.6 $ (483.7 ) $ 2,271.4 For the Nine Months Ended September 30, 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 $ 2,900.4 $ 395.9 $ — $ 100.9 $ — $ — $ 3,397.2 Commercial 2,023.0 245.4 — 47.9 — (3.4 ) 2,312.9 Industrial 268.6 71.9 — 3.4 — (7.5 ) 336.4 Total Retail Tariff Sales Revenue 5,192.0 713.2 — 152.2 — (10.9 ) 6,046.5 Wholesale Transmission Revenue — — 988.9 — 34.4 (826.9 ) 196.4 Wholesale Market Sales Revenue 141.4 41.4 — 3.1 — — 185.9 Other Revenue from Contracts with Customers 54.4 (1.4 ) 9.4 5.4 658.1 (659.8 ) 66.1 Reserve for Revenue Subject to Refund (21.2 ) (11.5 ) — (3.3 ) — — (36.0 ) Total Revenue from Contracts with Customers 5,366.6 741.7 998.3 157.4 692.5 (1,497.6 ) 6,458.9 Alternative Revenue Programs (57.2 ) (3.2 ) (45.3 ) 3.7 — 41.5 (60.5 ) Other Revenue 12.4 2.0 — 0.4 — — 14.8 Total Operating Revenues $ 5,321.8 $ 740.5 $ 953.0 $ 161.5 $ 692.5 $ (1,456.1 ) $ 6,413.2 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenue from Contracts with Customers Retail Tariff Sales Residential $ 539.6 $ 414.8 $ 157.3 $ 1,410.0 $ 1,071.6 $ 418.8 Commercial 259.0 443.8 87.3 702.2 1,083.8 238.4 Industrial 39.4 38.0 21.3 111.8 96.9 59.9 Total Retail Tariff Sales Revenue 838.0 896.6 265.9 2,224.0 2,252.3 717.1 Wholesale Transmission Revenue 179.1 128.3 57.1 469.8 367.7 151.4 Wholesale Market Sales Revenue 13.3 18.1 17.4 34.3 56.4 52.3 Other Revenue from Contracts with Customers 9.3 10.3 4.0 25.0 27.9 11.4 Reserve for Revenue Subject to Refund 8.3 — (3.1 ) (8.3 ) (3.7 ) (9.2 ) Total Revenue from Contracts with Customers 1,048.0 1,053.3 341.3 2,744.8 2,700.6 923.0 Alternative Revenue Programs (64.3 ) (15.4 ) (8.9 ) (68.4 ) (15.6 ) (18.5 ) Other Revenue 2.8 1.8 0.2 6.5 5.1 0.8 Eliminations (121.5 ) (100.2 ) (42.4 ) (338.0 ) (289.8 ) (112.6 ) Total Operating Revenues $ 865.0 $ 939.5 $ 290.2 $ 2,344.9 $ 2,400.3 $ 792.7 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. Eversource established a liability, 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, until rates billed to customers reflect the lower federal tax rate. Eversource expects to refund these amounts to customers through various rate mechanisms in the future, depending on regulatory outcomes, and CL&P began refunding these amounts in the third quarter of 2018. NSTAR Electric (effective February 1, 2018), CL&P (effective May 1, 2018) and NSTAR Gas (effective July 1, 2018) lowered distribution rates charged to customers to reflect the new federal corporate income tax rate. PSNH will adjust distribution rates to reflect the lower federal income tax rate, effective July 1, 2019, or earlier if a rate case is filed for rates effective prior to July 1, 2019. As part of Yankee Gas' rate case settlement, if approved, distribution rates will be adjusted to reflect the lower federal income tax rate, effective November 15, 2018. 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 the 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 mechanisms 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	9 Months Ended
	Sep. 30, 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 prior to sales in January and August 2018, 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 and PBOP expense. Eversource's segment information is as follows: For the Three Months Ended September 30, 2018 (1) Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 2,027.4 $ 109.0 $ 330.6 $ 63.5 $ 224.6 $ (483.7 ) $ 2,271.4 Depreciation and Amortization (206.1 ) (13.9 ) (58.3 ) (11.7 ) (12.0 ) 0.6 (301.4 ) Other Operating Expenses (1,562.2 ) (102.4 ) (96.7 ) (25.5 ) (200.9 ) 483.7 (1,504.0 ) Operating Income/(Loss) $ 259.1 $ (7.3 ) $ 175.6 $ 26.3 $ 11.7 $ 0.6 $ 466.0 Interest Expense $ (52.4 ) $ (11.3 ) $ (30.3 ) $ (8.5 ) $ (30.5 ) $ 7.8 $ (125.2 ) Other Income, Net 32.2 1.5 9.0 0.7 251.7 (278.4 ) 16.7 Net Income/(Loss) Attributable to Common Shareholders 173.8 (12.6 ) 109.5 17.6 271.1 (270.0 ) 289.4 For the Nine Months Ended September 30, 2018 (1) Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 5,321.8 $ 740.5 $ 953.0 $ 161.5 $ 692.5 $ (1,456.1 ) $ 6,413.2 Depreciation and Amortization (486.0 ) (59.6 ) (171.8 ) (34.6 ) (35.9 ) 1.7 (786.2 ) Other Operating Expenses (4,238.6 ) (585.7 ) (268.7 ) (73.9 ) (617.2 ) 1,457.0 (4,327.1 ) Operating Income $ 597.2 $ 95.2 $ 512.5 $ 53.0 $ 39.4 $ 2.6 $ 1,299.9 Interest Expense $ (152.0 ) $ (33.7 ) $ (89.9 ) $ (25.5 ) $ (94.8 ) $ 23.2 $ (372.7 ) Other Income/(Loss), Net 70.9 5.1 26.7 (0.4 ) 913.8 (915.4 ) 100.7 Net Income Attributable to Common Shareholders 379.3 50.2 329.6 26.3 905.9 (889.6 ) 801.7 Cash Flows Used for Investments in Plant 717.4 245.5 735.8 68.1 118.3 — 1,885.1 For the Three Months Ended September 30, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,547.1 $ 109.2 $ 328.5 $ — $ 224.2 $ (220.5 ) $ 1,988.5 Depreciation and Amortization (159.6 ) (15.2 ) (52.6 ) — (9.5 ) 0.6 (236.3 ) Other Operating Expenses (1,095.2 ) (96.2 ) (95.5 ) — (190.1 ) 220.1 (1,256.9 ) Operating Income/(Loss) $ 292.3 $ (2.2 ) $ 180.4 $ — $ 24.6 $ 0.2 $ 495.3 Interest Expense $ (51.3 ) $ (10.8 ) $ (29.2 ) $ — $ (21.8 ) $ 4.4 $ (108.7 ) Other Income, Net 14.2 1.0 8.5 — 267.6 (262.8 ) 28.5 Net Income/(Loss) Attributable to Common Shareholders 157.4 (6.2 ) 99.0 — 268.4 (258.2 ) 260.4 For the Nine Months Ended September 30, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 4,224.2 $ 698.8 $ 970.0 $ — $ 677.5 $ (714.0 ) $ 5,856.5 Depreciation and Amortization (394.9 ) (54.8 ) (154.5 ) — (26.7 ) 1.7 (629.2 ) Other Operating Expenses (3,076.1 ) (537.3 ) (280.6 ) — (602.9 ) 714.0 (3,782.9 ) Operating Income $ 753.2 $ 106.7 $ 534.9 $ — $ 47.9 $ 1.7 $ 1,444.4 Interest Expense $ (149.0 ) $ (32.3 ) $ (86.1 ) $ — $ (63.1 ) $ 11.0 $ (319.5 ) Other Income, Net 35.3 2.9 20.3 — 854.4 (833.7 ) 79.2 Net Income Attributable to Common Shareholders 393.4 49.1 289.6 — 839.5 (821.0 ) 750.6 Cash Flows Used for Investments in Plant 752.4 209.8 575.6 — 104.5 — 1,642.3 (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 16, "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 September 30, 2018 $ 21,189.0 $ 3,747.4 $ 10,077.5 $ 2,240.3 $ 16,979.4 $ (16,717.9 ) $ 37,515.7 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	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
ACQUISITION OF AQUARION	ACQUISITION OF AQUARION On December 4, 2017, Eversource acquired Aquarion for a purchase price of $1.675 billion , consisting of approximately $880 million in cash and $795 million of assumed Aquarion debt. Aquarion is a holding company that owns three separate regulated water utility subsidiaries engaged in the water collection, treatment and distribution business that operate 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 plus a $135 million shareholder loan that was repaid at closing. Purchase Price Allocation : The purchase price allocation reflects a measurement period adjustment recorded in the first quarter of 2018 to revise the fair value of Aquarion's regulated debt. The $7.9 million increase to the fair value of Long-Term Debt (including the current portion) 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 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 ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 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 (Topic 842) , which changes existing lease accounting guidance and is required to be applied in the first quarter of 2019, with earlier application permitted. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) - Targeted Improvements , allowing a transition method to adopt the new leases standard as of the adoption date and recognizing a cumulative-effect to the opening balance of retained earnings in the period of adoption, with comparative periods presented in the financial statements continuing to follow existing lease accounting guidance under Topic 840 (Leases) in the accounting literature. The Company intends to adopt the transition method allowed in ASU 2018-11. The Company will implement the new leases standard in the first quarter of 2019 and apply the Topic 842 lease criteria to new leases and lease renewals entered into effective on or after January 1, 2019. The requirements of the new leases standard 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, including the practical expedients, will have on its financial statements, including reviewing its lease population. The Company has decided to elect the practical expedient package whereby it need not reassess whether a contract is or contains a lease or whether a lease is an operating or capital lease and it need not reassess initial direct costs for leases. 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 16, "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 $0.4 million and $22.4 million , respectively, for the three and nine months ended September 30, 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. Unrealized gains recorded in Other Income, Net were $2.4 million and $2.6 million for the three and nine months ended September 30, 2018 , respectively. 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, SERP 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 September 30, 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 $30 million , as these amounts continue to be included in rates. See Note 1G, "Summary of Significant Accounting Policies - Other Income, Net," to the financial statements for the portion of pension, SERP and PBOP costs that are presented as non-operating income for the three and nine months ended September 30, 2018 and 2017 . For the three months ended September 30, 2017, the amounts, which were previously presented within Operations and Maintenance expense on the statements of income, totaled $7.3 million at Eversource, $0.4 million at CL&P, $4.7 million at NSTAR Electric and $1.5 million at PSNH, and have been retrospectively presented within Other Income, Net. For the nine months ended September 30, 2017, these amounts were $22.9 million at Eversource, $1.3 million at CL&P, $14.5 million at NSTAR Electric and $4.5 million at PSNH. 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 $16.4 million and $14.0 million for the nine months ended September 30, 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 1I, "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.
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, long-term debt and RRBs. 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 ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 As of December 31, 2017 As of September 30, 2018 As of December 31, 2017 Eversource $ 218.1 $ 195.7 $ 132.6 $ 122.5 CL&P 84.6 78.9 68.3 65.5 NSTAR Electric 82.0 69.7 46.5 40.3 PSNH 11.3 10.5 — — In accordance with new revenue accounting guidance, uncollectible expense associated with customers' accounts receivable included in Operations and Maintenance expense on the statements of income is as follows: For the Three Months Ended For the Nine Months Ended (Millions of Dollars) September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 Eversource $ 21.5 $ 14.4 $ 50.7 $ 30.1 CL&P 4.4 3.6 12.1 1.8 NSTAR Electric 9.1 8.1 20.4 14.9 PSNH 1.6 1.5 4.9 5.2
Schedule of Other Income, Net	The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended September 30, 2018 September 30, 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) $ 14.8 $ 2.0 $ 9.0 $ 2.0 $ 7.3 $ 0.4 $ 4.7 $ 1.5 AFUDC Equity 12.0 3.3 4.2 — 9.2 3.3 2.7 — Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates (2) (27.9 ) — 0.2 — 5.1 — 0.3 — Investment Income/(Loss) 1.8 0.7 (0.4 ) 0.1 4.6 3.1 0.9 0.7 Interest Income (3) 10.8 0.9 0.2 9.6 2.3 1.1 0.6 0.5 Gain on Sale of Property 5.0 — 0.5 4.4 — — — — Other 0.2 0.2 — — — — — — Total Other Income, Net (1) $ 16.7 $ 7.1 $ 13.7 $ 16.1 $ 28.5 $ 7.9 $ 9.2 $ 2.7 For the Nine Months Ended September 30, 2018 September 30, 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) $ 44.6 $ 7.3 $ 26.8 $ 6.4 $ 22.9 $ 1.3 $ 14.5 $ 4.5 AFUDC Equity 32.6 9.4 11.5 — 23.8 8.2 6.7 — Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates (2) (0.4 ) — 0.6 — 23.0 — 0.2 — Investment Income 2.2 0.9 0.6 0.2 3.7 2.4 2.1 1.2 Interest Income (3) 16.2 2.9 0.6 13.3 5.8 3.5 1.1 1.6 Gain on Sale of Property 5.0 — 0.5 4.4 — — — — Other 0.5 0.2 — — — — — 0.1 Total Other Income, Net (1) $ 100.7 $ 20.7 $ 40.6 $ 24.3 $ 79.2 $ 15.4 $ 24.6 $ 7.4 (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 within Other Income, Net for the three and nine months ended September 30, 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. (2) For the three months ended September 30, 2018 , equity in earnings/(loss) and impairment of unconsolidated affiliates includes an other-than-temporary impairment of $32.9 million in the Access Northeast project investment. See Note 1D, "Summary of Significant Accounting Policies - Impairment of Access Northeast," for further information. For the nine months ended September 30, 2018 and 2017, equity in earnings includes $17.6 million and $9.7 million of unrealized gains associated with an investment in a renewable energy fund, respectively. (3) See Note 2, "Regulatory Accounting," for interest income recognized in the third quarter of 2018 for the equity return component of carrying charges on storm costs at PSNH.
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 For the Nine Months Ended (Millions of Dollars) September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 Eversource $ 43.5 $ 40.3 $ 122.5 $ 118.2 CL&P 40.6 37.8 107.7 103.5
Schedule of Supplemental Cash Flow Information	Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of September 30, 2018 As of September 30, 2017 Eversource $ 303.7 $ 307.7 CL&P 103.0 113.4 NSTAR Electric 62.5 92.5 PSNH 48.3 39.6
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 September 30, 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 $ 59.1 $ 1.0 $ 2.4 $ 7.5 $ 38.2 $ 6.0 $ 1.8 $ 0.9 Restricted cash included in: Prepayments and Other Current Assets 51.4 3.5 12.9 26.8 24.4 3.1 12.8 0.5 Marketable Securities 20.9 0.4 0.1 0.7 23.3 0.5 0.1 0.8 Other Long-Term Assets 3.2 — — 3.2 — — — — Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows $ 134.6 $ 4.9 $ 15.4 $ 38.2 $ 85.9 $ 9.6 $ 14.7 $ 2.2

REGULATORY ACCOUNTING (Tables)

REGULATORY ACCOUNTING (Tables)	9 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
Schedule of Regulatory Assets	The components of regulatory assets were as follows: As of September 30, 2018 As of December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Benefit Costs $ 1,988.4 $ 447.4 $ 541.2 $ 172.0 $ 2,068.8 $ 469.2 $ 560.7 $ 212.3 Income Taxes, Net 720.7 448.1 112.9 15.6 768.9 453.8 113.2 21.7 Securitized Stranded Costs 618.6 — — 618.6 — — — — Deferred Costs from Generation Asset Sale — — — — 516.1 — — 516.1 Storm Restoration Costs, Net 598.5 319.7 222.1 56.7 404.8 216.7 146.6 41.5 Regulatory Tracker Mechanisms 257.8 39.5 128.4 74.9 509.9 85.3 273.0 116.4 Derivative Liabilities 360.0 359.9 — — 367.2 362.3 — — Goodwill-related 352.6 — 302.7 — 365.2 — 313.6 — Asset Retirement Obligations 87.5 31.8 41.3 3.3 101.0 30.3 39.0 17.0 Other Regulatory Assets 169.2 27.4 71.7 12.4 137.4 27.6 78.4 15.8 Total Regulatory Assets 5,153.3 1,673.8 1,420.3 953.5 5,239.3 1,645.2 1,524.5 940.8 Less: Current Portion 436.7 128.8 193.5 61.4 741.9 200.3 333.9 130.1 Total Long-Term Regulatory Assets $ 4,716.6 $ 1,545.0 $ 1,226.8 $ 892.1 $ 4,497.4 $ 1,444.9 $ 1,190.6 $ 810.7
Schedule of Regulatory Liabilities	The components of regulatory liabilities were as follows: As of September 30, 2018 As of December 31, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Excess ADIT due to Tax Cuts and Jobs Act $ 2,876.9 $ 1,026.3 $ 1,100.5 $ 397.4 $ 2,882.0 $ 1,031.6 $ 1,087.9 $ 405.1 Cost of Removal 516.4 37.8 305.7 24.9 502.1 23.2 293.8 37.9 Benefit Costs 127.1 — 107.2 0.5 132.3 — 112.6 — Regulatory Tracker Mechanisms 345.6 111.9 168.3 38.5 136.7 34.6 77.8 5.0 AFUDC - Transmission 68.6 47.8 20.8 — 67.1 48.8 18.3 — Revenue Subject to Refund 36.2 8.3 3.7 9.4 — — — — Other Regulatory Liabilities 80.7 25.7 28.3 2.8 45.2 12.9 3.7 2.7 Total Regulatory Liabilities 4,051.5 1,257.8 1,734.5 473.5 3,765.4 1,151.1 1,594.1 450.7 Less: Current Portion 344.7 126.6 168.2 39.7 128.1 39.0 79.6 6.3 Total Long-Term Regulatory Liabilities $ 3,706.8 $ 1,131.2 $ 1,566.3 $ 433.8 $ 3,637.3 $ 1,112.1 $ 1,514.5 $ 444.4

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 As of December 31, 2017 (Millions of Dollars) Distribution - Electric $ 14,794.9 $ 14,410.5 Distribution - Natural Gas 3,371.2 3,244.2 Transmission - Electric 9,733.6 9,270.9 Distribution - Water 1,594.3 1,558.4 Solar 109.3 36.2 Utility 29,603.3 28,520.2 Other (1) 759.0 693.7 Property, Plant and Equipment, Gross 30,362.3 29,213.9 Less: Accumulated Depreciation Utility (7,065.4 ) (6,846.9 ) Other (325.4 ) (286.9 ) Total Accumulated Depreciation (7,390.8 ) (7,133.8 ) Property, Plant and Equipment, Net 22,971.5 22,080.1 Construction Work in Progress 1,996.2 1,537.4 Total Property, Plant and Equipment, Net $ 24,967.7 $ 23,617.5 As of September 30, 2018 As of December 31, 2017 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution $ 6,027.1 $ 6,651.1 $ 2,157.0 $ 5,888.3 $ 6,479.0 $ 2,083.4 Transmission 4,513.7 3,915.5 1,255.6 4,239.9 3,821.2 1,161.3 Solar — 109.3 — — 36.2 — Property, Plant and Equipment, Gross 10,540.8 10,675.9 3,412.6 10,128.2 10,336.4 3,244.7 Less: Accumulated Depreciation (2,297.4 ) (2,673.0 ) (762.1 ) (2,239.0 ) (2,550.2 ) (751.8 ) Property, Plant and Equipment, Net 8,243.4 8,002.9 2,650.5 7,889.2 7,786.2 2,492.9 Construction Work in Progress 510.3 573.2 176.0 381.8 460.3 149.4 Total Property, Plant and Equipment, Net $ 8,753.7 $ 8,576.1 $ 2,826.5 $ 8,271.0 $ 8,246.5 $ 2,642.3 (1) These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service.

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 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: Eversource Level 2 $ 0.8 $ (0.5 ) $ 0.3 $ — $ — $ — CL&P Level 3 8.8 (4.8 ) 4.0 9.5 (7.1 ) 2.4 Long-Term Derivative Assets: CL&P Level 3 75.0 (2.3 ) 72.7 71.9 (5.3 ) 66.6 Current Derivative Liabilities: Eversource Level 2 — — — (4.5 ) — (4.5 ) CL&P Level 3 (50.8 ) — (50.8 ) (54.4 ) — (54.4 ) Long-Term Derivative Liabilities: Eversource Level 2 (0.1 ) — (0.1 ) (0.4 ) — (0.4 ) CL&P Level 3 (385.8 ) — (385.8 ) (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 September 30, 2018 As of December 31, 2017 CL&P Range Period Covered Range Period Covered Capacity Prices $ 4.30 — 7.44 per kW-Month 2022-2026 $ 5.00 — 8.70 per kW-Month 2021 - 2026 Forward Reserve $ 0.95 — 2.00 per kW-Month 2019-2024 $ 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 September 30, For the Nine Months Ended September 30, (Millions of Dollars) 2018 2017 2018 2017 Derivatives, Net: Fair Value as of Beginning of Period $ (369.3 ) $ (394.8 ) $ (362.3 ) $ (420.5 ) Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities 1.2 (0.7 ) (27.0 ) (15.9 ) Settlements 8.2 13.9 29.4 54.8 Fair Value as of End of Period $ (359.9 ) $ (381.6 ) $ (359.9 ) $ (381.6 )

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 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 $ 292.8 $ 0.8 $ (2.7 ) $ 290.9 $ 284.9 $ 3.2 $ (1.1 ) $ 287.0
Investments Classified by Contractual Maturity Date	As of September 30, 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) $ 28.5 $ 28.5 One to five years 48.7 48.3 Six to ten years 61.8 61.2 Greater than ten years 153.8 152.9 Total Debt Securities $ 292.8 $ 290.9 (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 September 30, 2018 As of December 31, 2017 Level 1: Mutual Funds and Equities $ 312.5 $ 313.8 Money Market Funds 20.9 23.3 Total Level 1 $ 333.4 $ 337.1 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 80.8 $ 70.2 Corporate Debt Securities 41.8 50.9 Asset-Backed Debt Securities 14.3 21.2 Municipal Bonds 121.2 110.7 Other Fixed Income Securities 11.9 10.7 Total Level 2 $ 270.0 $ 263.7 Total Marketable Securities $ 603.4 $ 600.8

SHORT-TERM AND LONG-TERM DEBT (

SHORT-TERM AND LONG-TERM DEBT (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Commercial Paper Program	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 September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (Millions of Dollars) Eversource Parent Commercial Paper Program $ 826.7 $ 979.3 $ 623.3 $ 470.7 2.34 % 1.86 % NSTAR Electric Commercial Paper Program 240.5 234.0 409.5 416.0 2.17 % 1.55 %
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 for Issuances/ CL&P: 4.00% 2018 Series A First Mortgage Bonds March 2018 $ 500.0 April 2048 Repaid long-term debt that matured in 2018 and repaid short-term borrowings 5.65% 2008 Series A First Mortgage Bonds May 2008 (300.0 ) May 2018 Repaid at maturity on May 1, 2018 PSNH: 6.00% 2008 Series O First Mortgage Bonds May 2008 (110.0 ) May 2018 Repaid at maturity on May 1, 2018 Other: Eversource Parent 2.50% Series I Senior Notes (1) January 2018 200.0 March 2021 Repaid long-term debt that matured in 2018 and repaid short-term borrowings Eversource Parent 3.30% Series M Senior Notes January 2018 450.0 January 2028 Repaid long-term debt that matured in 2018 Eversource Parent 1.60% Series G Senior Notes January 2015 (150.0 ) January 2018 Repaid at maturity on January 15, 2018 Eversource Parent 1.45% Series E Senior Notes May 2013 (300.0 ) May 2018 Repaid at maturity on May 1, 2018 Yankee Gas 4.13% Series O First Mortgage Bonds September 2018 50.0 October 2048 Repaid long-term debt that matured in 2018 NSTAR Gas 4.09% Series P First Mortgage Bonds September 2018 100.0 October 2048 Repaid short-term borrowings Yankee Gas 6.90% Series J First Mortgage Bonds October 2018 (100.0 ) October 2018 Repaid at maturity on October 1, 2018 (1) 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 .

RATE REDUCTION BONDS AND VARI_2

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES (Tables)	9 Months Ended
	Sep. 30, 2018
Rate Reduction Bonds and Variable Interest Entity [Abstract]
Schedule of Variable Interest Entities	The following tables summarize the impact of PSNH Funding on PSNH's balance sheet and income statement: (Millions of Dollars) Balance Sheet: As of September 30, 2018 Restricted Cash - Current Portion (included in Prepayments and Other Current Assets) $ 26.9 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 3.2 Securitized Stranded Cost (included in Regulatory Assets) 618.6 Other Regulatory Liabilities (included in Regulatory Liabilities) 1.0 Accrued Interest (included in Other Current Liabilities) 8.8 Rate Reduction Bonds - Current Portion 52.3 Rate Reduction Bonds - Long-Term Portion 583.3 (Millions of Dollars) Income Statement: For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2018 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 10.2 $ 17.1 Interest Expense on RRB Principal (included in Interest Expense) 6.0 8.8

PENSION BENEFITS AND POSTRETI_2

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION (Tables)	9 Months Ended
	Sep. 30, 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 and deferred portion, as these amounts are cash settled on a short-term basis. Pension and SERP For the Three Months Ended September 30, 2018 For the Three Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 20.9 $ 5.2 $ 4.3 $ 2.7 $ 17.4 $ 4.6 $ 3.8 $ 2.4 Interest Cost 49.2 10.5 10.9 5.5 47.2 10.5 10.7 5.3 Expected Return on Plan Assets (97.8 ) (19.4 ) (26.6 ) (10.8 ) (83.5 ) (17.8 ) (21.9 ) (10.0 ) Actuarial Loss 35.7 7.1 10.1 3.3 33.9 6.8 10.4 3.0 Prior Service Cost 2.0 0.2 0.1 0.1 1.2 0.4 0.2 0.1 Total Net Periodic Benefit Expense/(Income) $ 10.0 $ 3.6 $ (1.2 ) $ 0.8 $ 16.2 $ 4.5 $ 3.2 $ 0.8 Intercompany Allocations N/A $ 1.5 $ 1.6 $ 0.5 N/A $ 2.4 $ 2.3 $ 0.8 Capitalized Pension Expense $ 6.6 $ 2.0 $ 1.8 $ 0.8 $ 5.5 $ 2.4 $ 2.0 $ 0.4 Pension and SERP For the Nine Months Ended September 30, 2018 For the Nine Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 64.2 $ 16.2 $ 13.1 $ 8.4 $ 53.8 $ 13.9 $ 11.7 $ 7.3 Interest Cost 147.1 31.4 32.6 16.4 140.7 31.3 31.9 15.9 Expected Return on Plan Assets (293.8 ) (59.7 ) (78.3 ) (32.6 ) (250.5 ) (53.9 ) (65.8 ) (29.9 ) Actuarial Loss 107.6 21.9 31.0 9.8 101.3 20.7 30.9 8.7 Prior Service Cost 6.0 0.8 0.2 0.2 3.4 1.1 0.4 0.4 Total Net Periodic Benefit Expense/(Income) $ 31.1 $ 10.6 $ (1.4 ) $ 2.2 $ 48.7 $ 13.1 $ 9.1 $ 2.4 Intercompany Allocations N/A $ 4.5 $ 4.8 $ 1.4 N/A $ 7.4 $ 6.9 $ 2.5 Capitalized Pension Expense $ 20.2 $ 6.2 $ 5.8 $ 2.3 $ 16.5 $ 7.3 $ 5.7 $ 1.1 PBOP For the Three Months Ended September 30, 2018 For the Three Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 2.5 $ 0.4 $ 0.5 $ 0.3 $ 2.4 $ 0.5 $ 0.4 $ 0.3 Interest Cost 7.7 1.5 2.2 0.9 6.8 1.3 2.2 0.8 Expected Return on Plan Assets (18.2 ) (2.6 ) (8.1 ) (1.5 ) (16.0 ) (2.4 ) (7.2 ) (1.4 ) Actuarial Loss 2.6 0.4 0.5 0.2 2.2 0.2 0.9 0.1 Prior Service Cost/(Credit) (6.0 ) 0.3 (4.3 ) 0.1 (5.3 ) 0.3 (4.3 ) 0.2 Total Net Periodic Benefit Income $ (11.4 ) $ — $ (9.2 ) $ — $ (9.9 ) $ (0.1 ) $ (8.0 ) $ — Intercompany Allocations N/A $ (0.3 ) $ (0.3 ) $ (0.1 ) N/A $ (0.2 ) $ (0.2 ) $ (0.1 ) Capitalized PBOP Expense/(Income) $ 0.7 $ 0.1 $ 0.2 $ 0.1 $ (4.8 ) $ (0.1 ) $ (4.1 ) $ — PBOP For the Nine Months Ended September 30, 2018 For the Nine Months Ended September 30, 2017 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 7.5 $ 1.4 $ 1.6 $ 0.9 $ 7.1 $ 1.5 $ 1.4 $ 1.0 Interest Cost 23.0 4.4 6.5 2.5 20.3 4.0 6.5 2.3 Expected Return on Plan Assets (54.2 ) (7.8 ) (24.4 ) (4.5 ) (47.8 ) (7.3 ) (21.6 ) (4.1 ) Actuarial Loss 7.7 1.2 1.7 0.6 6.9 0.7 2.6 0.4 Prior Service Cost/(Credit) (17.6 ) 0.8 (12.7 ) 0.4 (16.1 ) 0.8 (12.8 ) 0.4 Total Net Periodic Benefit Income $ (33.6 ) $ — $ (27.3 ) $ (0.1 ) $ (29.6 ) $ (0.3 ) $ (23.9 ) $ — Intercompany Allocations N/A $ (0.8 ) $ (1.0 ) $ (0.3 ) N/A $ (0.5 ) $ (0.8 ) $ (0.3 ) Capitalized PBOP Expense/(Income) $ 2.3 $ 0.5 $ 0.7 $ 0.3 $ (14.3 ) $ (0.4 ) $ (12.1 ) $ —

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 As of December 31, 2017 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 60 $ 66.6 59 $ 54.9 CL&P 14 5.0 14 4.7 NSTAR Electric 17 10.9 15 2.7 PSNH 9 5.5 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 September 30, 2018 : Company Description Maximum Exposure (in millions) Expiration Dates On behalf of subsidiaries: Eversource Gas Transmission LLC Access Northeast Project Capital Contributions Guaranty (1) $ 184.9 2021 Various Surety Bonds (2) 42.7 2018 - 2019 Eversource Service and Rocky River Realty Company Lease Payments for Vehicles and Real Estate 6.6 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 were 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 September 30, 2018 (in millions) First 10/1/2011 - 12/31/2012 11.14% 10.57% $— (2) Second 12/27/2012 - 3/26/2014 11.14% N/A 39.1 (3) Third 7/31/2014 - 10/30/2015 11.14% 10.57% — Fourth 4/29/2016 - 7/28/2017 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) All amounts associated with the first complaint period have been refunded, which totaled $38.9 million (pre-tax and excluding interest) at Eversource and reflected both the base ROE and incentive cap prescribed by the FERC order. The refund consisted of $22.4 million for CL&P, $13.7 million for NSTAR Electric and $2.8 million for PSNH. (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 September 30, 2018 .

ASSETS HELD FOR SALE (Tables)

ASSETS HELD FOR SALE (Tables)	9 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
Schedule of Generation Assets and Liabilities	As of September 30, 2018 , all generation assets had been sold and as a result, no generation assets were classified as held for sale. As of December 31, 2017, PSNH's generation assets held for sale, which were included in current assets on the Eversource and PSNH balance sheets, and were part of the Electric Distribution reportable segment, were as follows: (Millions of Dollars) As of December 31, 2017 Thermal Gross Plant $ 1,091.4 Hydroelectric Gross Plant 83.0 Accumulated Depreciation (575.4 ) Net Plant 599.0 Fuel and Inventory 87.7 Materials and Supplies 27.3 Emissions Allowances 19.1 Other Assets 2.6 Deferred Costs from Thermal Generation Asset Sale (516.1 ) Total Generation Assets Held for Sale $ 219.6

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	Carrying amounts and estimated fair values are as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of September 30, 2018: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 163.0 $ 116.2 $ 120.2 $ 43.0 $ 42.8 $ — $ — Long-Term Debt 12,538.8 12,517.4 3,253.6 3,420.4 2,944.6 2,990.0 894.1 904.3 Rate Reduction Bonds 635.7 631.3 — — — — 635.7 631.3 As of December 31, 2017: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 160.8 $ 116.2 $ 116.5 $ 43.0 $ 44.3 $ — $ — Long-Term Debt 12,325.5 12,877.1 3,059.1 3,430.5 2,943.8 3,156.5 1,002.4 1,038.2

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30, 2018 For the Nine Months Ended September 30, 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 — (0.7 ) 2.6 1.9 — 0.7 (3.5 ) (2.8 ) Amounts Reclassified from AOCI 1.6 — 3.3 4.9 1.6 — 2.9 4.5 Net OCI 1.6 (0.7 ) 5.9 6.8 1.6 0.7 (0.6 ) 1.7 Balance as of End of Period $ (4.6 ) $ (0.7 ) $ (54.3 ) $ (59.6 ) $ (6.6 ) $ 1.1 $ (58.1 ) $ (63.6 )

COMMON SHARES (Tables)

COMMON SHARES (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 and Issued as of Par Value December 31, 2017 September 30, 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)	9 Months Ended
	Sep. 30, 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 For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 Net Income Attributable to Common Shareholders $ 289.4 $ 260.4 $ 801.7 $ 750.6 Weighted Average Common Shares Outstanding: Basic 317,360,110 317,393,029 317,367,252 317,415,848 Dilutive Effect 607,201 556,367 581,246 591,194 Diluted 317,967,311 317,949,396 317,948,498 318,007,042 Basic EPS $ 0.91 $ 0.82 $ 2.53 $ 2.36 Diluted EPS $ 0.91 $ 0.82 $ 2.52 $ 2.36

REVENUES (Tables)

REVENUES (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 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 $ 1,111.7 $ 42.8 $ — $ 41.2 $ — $ — $ 1,195.7 Commercial 789.6 40.8 — 17.9 — (1.2 ) 847.1 Industrial 98.7 18.9 — 1.3 — (2.6 ) 116.3 Total Retail Tariff Sales Revenue 2,000.0 102.5 — 60.4 — (3.8 ) 2,159.1 Wholesale Transmission Revenue — — 364.5 — 11.7 (300.2 ) 76.0 Wholesale Market Sales Revenue 48.8 11.4 — 1.3 — — 61.5 Other Revenue from Contracts with Customers 20.2 (0.5 ) 3.1 1.9 212.9 (213.5 ) 24.1 Reserve for Revenue Subject to Refund 5.2 (3.5 ) — (1.3 ) — — 0.4 Total Revenue from Contracts with Customers 2,074.2 109.9 367.6 62.3 224.6 (517.5 ) 2,321.1 Alternative Revenue Programs (51.6 ) (1.5 ) (37.0 ) 1.1 — 33.8 (55.2 ) Other Revenue 4.8 0.6 — 0.1 — — 5.5 Total Operating Revenues $ 2,027.4 $ 109.0 $ 330.6 $ 63.5 $ 224.6 $ (483.7 ) $ 2,271.4 For the Nine Months Ended September 30, 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 $ 2,900.4 $ 395.9 $ — $ 100.9 $ — $ — $ 3,397.2 Commercial 2,023.0 245.4 — 47.9 — (3.4 ) 2,312.9 Industrial 268.6 71.9 — 3.4 — (7.5 ) 336.4 Total Retail Tariff Sales Revenue 5,192.0 713.2 — 152.2 — (10.9 ) 6,046.5 Wholesale Transmission Revenue — — 988.9 — 34.4 (826.9 ) 196.4 Wholesale Market Sales Revenue 141.4 41.4 — 3.1 — — 185.9 Other Revenue from Contracts with Customers 54.4 (1.4 ) 9.4 5.4 658.1 (659.8 ) 66.1 Reserve for Revenue Subject to Refund (21.2 ) (11.5 ) — (3.3 ) — — (36.0 ) Total Revenue from Contracts with Customers 5,366.6 741.7 998.3 157.4 692.5 (1,497.6 ) 6,458.9 Alternative Revenue Programs (57.2 ) (3.2 ) (45.3 ) 3.7 — 41.5 (60.5 ) Other Revenue 12.4 2.0 — 0.4 — — 14.8 Total Operating Revenues $ 5,321.8 $ 740.5 $ 953.0 $ 161.5 $ 692.5 $ (1,456.1 ) $ 6,413.2 For the Three Months Ended September 30, 2018 For the Nine Months Ended September 30, 2018 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenue from Contracts with Customers Retail Tariff Sales Residential $ 539.6 $ 414.8 $ 157.3 $ 1,410.0 $ 1,071.6 $ 418.8 Commercial 259.0 443.8 87.3 702.2 1,083.8 238.4 Industrial 39.4 38.0 21.3 111.8 96.9 59.9 Total Retail Tariff Sales Revenue 838.0 896.6 265.9 2,224.0 2,252.3 717.1 Wholesale Transmission Revenue 179.1 128.3 57.1 469.8 367.7 151.4 Wholesale Market Sales Revenue 13.3 18.1 17.4 34.3 56.4 52.3 Other Revenue from Contracts with Customers 9.3 10.3 4.0 25.0 27.9 11.4 Reserve for Revenue Subject to Refund 8.3 — (3.1 ) (8.3 ) (3.7 ) (9.2 ) Total Revenue from Contracts with Customers 1,048.0 1,053.3 341.3 2,744.8 2,700.6 923.0 Alternative Revenue Programs (64.3 ) (15.4 ) (8.9 ) (68.4 ) (15.6 ) (18.5 ) Other Revenue 2.8 1.8 0.2 6.5 5.1 0.8 Eliminations (121.5 ) (100.2 ) (42.4 ) (338.0 ) (289.8 ) (112.6 ) Total Operating Revenues $ 865.0 $ 939.5 $ 290.2 $ 2,344.9 $ 2,400.3 $ 792.7

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Eversource's segment information is as follows: For the Three Months Ended September 30, 2018 (1) Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 2,027.4 $ 109.0 $ 330.6 $ 63.5 $ 224.6 $ (483.7 ) $ 2,271.4 Depreciation and Amortization (206.1 ) (13.9 ) (58.3 ) (11.7 ) (12.0 ) 0.6 (301.4 ) Other Operating Expenses (1,562.2 ) (102.4 ) (96.7 ) (25.5 ) (200.9 ) 483.7 (1,504.0 ) Operating Income/(Loss) $ 259.1 $ (7.3 ) $ 175.6 $ 26.3 $ 11.7 $ 0.6 $ 466.0 Interest Expense $ (52.4 ) $ (11.3 ) $ (30.3 ) $ (8.5 ) $ (30.5 ) $ 7.8 $ (125.2 ) Other Income, Net 32.2 1.5 9.0 0.7 251.7 (278.4 ) 16.7 Net Income/(Loss) Attributable to Common Shareholders 173.8 (12.6 ) 109.5 17.6 271.1 (270.0 ) 289.4 For the Nine Months Ended September 30, 2018 (1) Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 5,321.8 $ 740.5 $ 953.0 $ 161.5 $ 692.5 $ (1,456.1 ) $ 6,413.2 Depreciation and Amortization (486.0 ) (59.6 ) (171.8 ) (34.6 ) (35.9 ) 1.7 (786.2 ) Other Operating Expenses (4,238.6 ) (585.7 ) (268.7 ) (73.9 ) (617.2 ) 1,457.0 (4,327.1 ) Operating Income $ 597.2 $ 95.2 $ 512.5 $ 53.0 $ 39.4 $ 2.6 $ 1,299.9 Interest Expense $ (152.0 ) $ (33.7 ) $ (89.9 ) $ (25.5 ) $ (94.8 ) $ 23.2 $ (372.7 ) Other Income/(Loss), Net 70.9 5.1 26.7 (0.4 ) 913.8 (915.4 ) 100.7 Net Income Attributable to Common Shareholders 379.3 50.2 329.6 26.3 905.9 (889.6 ) 801.7 Cash Flows Used for Investments in Plant 717.4 245.5 735.8 68.1 118.3 — 1,885.1 For the Three Months Ended September 30, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,547.1 $ 109.2 $ 328.5 $ — $ 224.2 $ (220.5 ) $ 1,988.5 Depreciation and Amortization (159.6 ) (15.2 ) (52.6 ) — (9.5 ) 0.6 (236.3 ) Other Operating Expenses (1,095.2 ) (96.2 ) (95.5 ) — (190.1 ) 220.1 (1,256.9 ) Operating Income/(Loss) $ 292.3 $ (2.2 ) $ 180.4 $ — $ 24.6 $ 0.2 $ 495.3 Interest Expense $ (51.3 ) $ (10.8 ) $ (29.2 ) $ — $ (21.8 ) $ 4.4 $ (108.7 ) Other Income, Net 14.2 1.0 8.5 — 267.6 (262.8 ) 28.5 Net Income/(Loss) Attributable to Common Shareholders 157.4 (6.2 ) 99.0 — 268.4 (258.2 ) 260.4 For the Nine Months Ended September 30, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 4,224.2 $ 698.8 $ 970.0 $ — $ 677.5 $ (714.0 ) $ 5,856.5 Depreciation and Amortization (394.9 ) (54.8 ) (154.5 ) — (26.7 ) 1.7 (629.2 ) Other Operating Expenses (3,076.1 ) (537.3 ) (280.6 ) — (602.9 ) 714.0 (3,782.9 ) Operating Income $ 753.2 $ 106.7 $ 534.9 $ — $ 47.9 $ 1.7 $ 1,444.4 Interest Expense $ (149.0 ) $ (32.3 ) $ (86.1 ) $ — $ (63.1 ) $ 11.0 $ (319.5 ) Other Income, Net 35.3 2.9 20.3 — 854.4 (833.7 ) 79.2 Net Income Attributable to Common Shareholders 393.4 49.1 289.6 — 839.5 (821.0 ) 750.6 Cash Flows Used for Investments in Plant 752.4 209.8 575.6 — 104.5 — 1,642.3 (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 16, "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 September 30, 2018 $ 21,189.0 $ 3,747.4 $ 10,077.5 $ 2,240.3 $ 16,979.4 $ (16,717.9 ) $ 37,515.7 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)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Schedule of Business Acquisition by Acquisition	The 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 ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands, customer in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)customerutilityMW	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Number of electric and natural gas customers | customer			4
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	$ 400		$ 22,400
Unrealized losses recorded in other income	2,400		2,600
Increase in regulatory liabilities			30,000
Other Income, Net	16,718	$ 28,536	$ 100,656	$ 79,178
Capacity required for transmission line | MW			1,090
Amount capitalized in transmission line installation			$ 302,000
Other than temporary impairment	32,900
Expenses recorded as taxes other than income taxes	10,700		36,100
Change in enacted tax rate	18,000
Accounting Standards Update 2016-15
Schedule of Equity Method Investments [Line Items]
Dividends from equity method investment			16,400	14,000
New accounting guidance for statement of cash flows
Schedule of Equity Method Investments [Line Items]
Restricted cash		(30,200)		(30,200)
The Connecticut Light and Power Company
Schedule of Equity Method Investments [Line Items]
Other Income, Net	7,098	7,913	20,722	15,402
NSTAR Electric Company
Schedule of Equity Method Investments [Line Items]
Other Income, Net	13,697	9,165	40,567	24,610
Public Service Company of New Hampshire
Schedule of Equity Method Investments [Line Items]
Other Income, Net	16,095	2,664	24,253	7,367
Non-Service Cost Benefits
Schedule of Equity Method Investments [Line Items]
Other Income, Net	14,800	7,300	44,600	22,900
Non-Service Cost Benefits | The Connecticut Light and Power Company
Schedule of Equity Method Investments [Line Items]
Other Income, Net	2,000	400	7,300	1,300
Non-Service Cost Benefits | NSTAR Electric Company
Schedule of Equity Method Investments [Line Items]
Other Income, Net	9,000	4,700	26,800	14,500
Non-Service Cost Benefits | Public Service Company of New Hampshire
Schedule of Equity Method Investments [Line Items]
Other Income, Net	$ 2,000	$ 1,500	$ 6,400	$ 4,500
Connecticut, Massachusetts and New Hampshire
Schedule of Equity Method Investments [Line Items]
Number of regulated utilities | utility			8
Access Northeast
Schedule of Equity Method Investments [Line Items]
Ownership percentage by parent	40.00%		40.00%

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	$ 218,100		$ 218,100		$ 195,700
Uncollectible Hardship	132,600		132,600		122,500
Bad debt expense associated with accounts receivable	21,500	$ 14,400	$ 50,720	$ 30,111
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
Total Provision for Uncollectible Accounts	84,600		$ 84,600		78,900
Uncollectible Hardship	68,300		68,300		65,500
Bad debt expense associated with accounts receivable	4,400	3,600	$ 12,135	1,755
Yankee Gas Services Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of accounts receivable recoverable under financial or medical duress			90 days
NSTAR Electric Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	82,000		$ 82,000		69,700
Uncollectible Hardship	46,500		46,500		40,300
Bad debt expense associated with accounts receivable	9,100	8,100	20,433	14,937
Public Service Company of New Hampshire
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	11,300		11,300		10,500
Uncollectible Hardship	0		0		$ 0
Bad debt expense associated with accounts receivable	$ 1,600	$ 1,500	$ 4,900	$ 5,200

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Summary of Accounting Policies [Line Items]
Other Income, Net	$ 16,718	$ 28,536	$ 100,656	$ 79,178
Equity securities, unrealized gain (loss)	17,600	9,700	0	0
Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	14,800	7,300	44,600	22,900
AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	12,000	9,200	32,600	23,800
Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net	(27,900)	5,100	(400)	23,000
Investment Income
Summary of Accounting Policies [Line Items]
Other Income, Net	1,800	4,600	2,200	3,700
Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	10,800	2,300	16,200	5,800
Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other Income, Net	5,000	0	5,000	0
Other
Summary of Accounting Policies [Line Items]
Other Income, Net	200	0	500	0
The Connecticut Light and Power Company
Summary of Accounting Policies [Line Items]
Other Income, Net	7,098	7,913	20,722	15,402
The Connecticut Light and Power Company | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	2,000	400	7,300	1,300
The Connecticut Light and Power Company | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	3,300	3,300	9,400	8,200
The Connecticut Light and Power Company | Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0	0	0
The Connecticut Light and Power Company | Investment Income
Summary of Accounting Policies [Line Items]
Other Income, Net	700	3,100	900	2,400
The Connecticut Light and Power Company | Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	900	1,100	2,900	3,500
The Connecticut Light and Power Company | Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other Income, Net		0		0
The Connecticut Light and Power Company | Other
Summary of Accounting Policies [Line Items]
Other Income, Net	200	0	200	0
NSTAR Electric Company
Summary of Accounting Policies [Line Items]
Other Income, Net	13,697	9,165	40,567	24,610
NSTAR Electric Company | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	9,000	4,700	26,800	14,500
NSTAR Electric Company | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	4,200	2,700	11,500	6,700
NSTAR Electric Company | Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net	200	300	600	200
NSTAR Electric Company | Investment Income
Summary of Accounting Policies [Line Items]
Other Income, Net	(400)	900	600	2,100
NSTAR Electric Company | Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	200	600	600	1,100
NSTAR Electric Company | Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other Income, Net	500	0	500	0
NSTAR Electric Company | Other
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0	0	0
Public Service Company of New Hampshire
Summary of Accounting Policies [Line Items]
Other Income, Net	16,095	2,664	24,253	7,367
Public Service Company of New Hampshire | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other Income, Net	2,000	1,500	6,400	4,500
Public Service Company of New Hampshire | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0	0	0
Public Service Company of New Hampshire | Equity in Earnings/(Loss) and Impairment of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other Income, Net	0	0	0	0
Public Service Company of New Hampshire | Investment Income
Summary of Accounting Policies [Line Items]
Other Income, Net	100	700	200	1,200
Public Service Company of New Hampshire | Interest Income
Summary of Accounting Policies [Line Items]
Other Income, Net	9,600	500	13,300	1,600
Public Service Company of New Hampshire | Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other Income, Net	4,400	0	4,400	0
Public Service Company of New Hampshire | Other
Summary of Accounting Policies [Line Items]
Other Income, Net	$ 0	$ 0	$ 0	$ 100

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Expenses recorded as taxes other than income taxes	$ 10.7		$ 36.1
Schedule of Gross Tax Receipts [Line Items]
Excise and sales taxes	43.5	$ 40.3	122.5	$ 118.2
The Connecticut Light and Power Company
Schedule of Gross Tax Receipts [Line Items]
Excise and sales taxes	$ 40.6	$ 37.8	$ 107.7	$ 103.5

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Supplemental Cash Flow (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	$ 303.7	$ 307.7
The Connecticut Light and Power Company
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	103	113.4
NSTAR Electric Company
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	62.5	92.5
Public Service Company of New Hampshire
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	$ 48.3	$ 39.6

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	$ 59,092	$ 38,165
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	134,605	85,890	$ 171,976	$ 106,750
Prepayments and Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	51,400	24,400
Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	20,900	23,300
Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	3,200	0
The Connecticut Light and Power Company
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	977	6,028
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	4,880	9,619	12,916	8,403
The Connecticut Light and Power Company | Prepayments and Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	3,500	3,100
The Connecticut Light and Power Company | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	400	500
The Connecticut Light and Power Company | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
NSTAR Electric Company
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	2,367	1,763
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	15,361	14,708	102,813	15,506
NSTAR Electric Company | Prepayments and Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	12,900	12,800
NSTAR Electric Company | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	100	100
NSTAR Electric Company | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
Public Service Company of New Hampshire
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	7,462	900
Cash, Cash Equivalents, and Restricted Cash reported on the Statements of Cash Flows	38,166	2,191	$ 1,834	$ 5,953
Public Service Company of New Hampshire | Prepayments and Other Current Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	26,800	500
Public Service Company of New Hampshire | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	700	800
Public Service Company of New Hampshire | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 3,200	$ 0

REGULATORY ACCOUNTING - Compone

REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 5,153,300	$ 5,239,300
Less: Current Portion	436,704	741,868
Total Long-Term Regulatory Assets	4,716,631	4,497,447
Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	1,988,400	2,068,800
Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	720,700	768,900
Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	618,600	0
Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Total Regulatory Assets	0	516,100
Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	598,500	404,800
Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	257,800	509,900
Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	360,000	367,200
Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	352,600	365,200
Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	87,500	101,000
Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	169,200	137,400
The Connecticut Light and Power Company
Regulatory Assets [Line Items]
Total Regulatory Assets	1,673,800	1,645,200
Less: Current Portion	128,793	200,281
Total Long-Term Regulatory Assets	1,545,012	1,444,935
The Connecticut Light and Power Company | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	447,400	469,200
The Connecticut Light and Power Company | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	448,100	453,800
The Connecticut Light and Power Company | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
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	319,700	216,700
The Connecticut Light and Power Company | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	39,500	85,300
The Connecticut Light and Power Company | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	359,900	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	31,800	30,300
The Connecticut Light and Power Company | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	27,400	27,600
NSTAR Electric Company
Regulatory Assets [Line Items]
Total Regulatory Assets	1,420,300	1,524,500
Less: Current Portion	193,541	333,882
Total Long-Term Regulatory Assets	1,226,811	1,190,575
NSTAR Electric Company | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	541,200	560,700
NSTAR Electric Company | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	112,900	113,200
NSTAR Electric Company | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
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	222,100	146,600
NSTAR Electric Company | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	128,400	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	302,700	313,600
NSTAR Electric Company | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	41,300	39,000
NSTAR Electric Company | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	71,700	78,400
Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Total Regulatory Assets	953,500	940,800
Less: Current Portion	61,379	130,134
Total Long-Term Regulatory Assets	892,075	810,677
Public Service Company of New Hampshire | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	172,000	212,300
Public Service Company of New Hampshire | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	15,600	21,700
Public Service Company of New Hampshire | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	618,600	0
Public Service Company of New Hampshire | Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Total Regulatory Assets	0	516,100
Public Service Company of New Hampshire | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	56,700	41,500
Public Service Company of New Hampshire | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	74,900	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	3,300	17,000
Public Service Company of New Hampshire | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 12,400	$ 15,800

REGULATORY ACCOUNTING - Narrati

REGULATORY ACCOUNTING - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 17, 2018	May 08, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Regulatory assets	$ 5,153,300		$ 5,153,300				$ 5,239,300
Other Income, Net	16,718	$ 28,536	100,656	$ 79,178
Amount of regulatory costs not yet approved	104,600		104,600				105,800
Regulatory liabilities	4,051,500		4,051,500				3,765,400
Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Regulatory assets	953,500		953,500				940,800
Amount of recovery approved					$ 49,000
Other Income, Net	16,095	2,664	24,253	7,367
Amount of regulatory costs not yet approved	3,900		3,900				27,200
Regulatory liabilities	473,500		473,500				450,700
The Connecticut Light and Power Company
Regulatory Assets [Line Items]
Regulatory assets	1,673,800		1,673,800				1,645,200
Other Income, Net	7,098	7,913	20,722	15,402
Amount of regulatory costs not yet approved	27,600		27,600				18,200
Regulatory liabilities	1,257,800		1,257,800				1,151,100
NSTAR Electric Company
Regulatory Assets [Line Items]
Regulatory assets	1,420,300		1,420,300				1,524,500
Other Income, Net	13,697	$ 9,165	40,567	$ 24,610
Amount of regulatory costs not yet approved	53,300		53,300				42,700
Regulatory liabilities	1,734,500		1,734,500				1,594,100
Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Regulatory assets	266,000		266,000
Deferred Costs from Generation Asset Sale | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Regulatory assets	16,000		16,000
Other Income, Net	8,700
Deferred Costs from Generation Asset Sale | The Connecticut Light and Power Company
Regulatory Assets [Line Items]
Regulatory assets	149,000		149,000
Deferred Costs from Generation Asset Sale | NSTAR Electric Company
Regulatory Assets [Line Items]
Regulatory assets	101,000		101,000
Rate Reduction Bonds | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Amount of securitized rate reduction bonds issued						$ 635,700
Revenue Subject to Refund
Regulatory Assets [Line Items]
Regulatory liabilities	36,200		36,200				0
Revenue Subject to Refund | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Regulatory liabilities	9,400		9,400				0
Revenue Subject to Refund | The Connecticut Light and Power Company
Regulatory Assets [Line Items]
Regulatory liabilities	8,300		8,300				0
Revenue Subject to Refund | NSTAR Electric Company
Regulatory Assets [Line Items]
Regulatory liabilities	$ 3,700		$ 3,700				$ 0

REGULATORY ACCOUNTING - Compo_2

REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 4,051,500	$ 3,765,400
Less: Current Portion	344,708	128,071
Total Long-Term Regulatory Liabilities	3,706,792	3,637,273
Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	2,876,900	2,882,000
Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	516,400	502,100
Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	127,100	132,300
Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	345,600	136,700
AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	68,600	67,100
Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	36,200	0
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	80,700	45,200
The Connecticut Light and Power Company
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,257,800	1,151,100
Less: Current Portion	126,574	38,967
Total Long-Term Regulatory Liabilities	1,131,234	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	1,026,300	1,031,600
The Connecticut Light and Power Company | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	37,800	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	111,900	34,600
The Connecticut Light and Power Company | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	47,800	48,800
The Connecticut Light and Power Company | Revenue Subject to Refund
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	8,300	0
The Connecticut Light and Power Company | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	25,700	12,900
NSTAR Electric Company
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,734,500	1,594,100
Less: Current Portion	168,225	79,562
Total Long-Term Regulatory Liabilities	1,566,285	1,514,451
NSTAR Electric Company | Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,100,500	1,087,900
NSTAR Electric Company | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	305,700	293,800
NSTAR Electric Company | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	107,200	112,600
NSTAR Electric Company | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	168,300	77,800
NSTAR Electric Company | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	20,800	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	28,300	3,700
Public Service Company of New Hampshire
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	473,500	450,700
Less: Current Portion	39,661	6,251
Total Long-Term Regulatory Liabilities	433,822	444,397
Public Service Company of New Hampshire | Excess ADIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	397,400	405,100
Public Service Company of New Hampshire | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	24,900	37,900
Public Service Company of New Hampshire | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	500	0
Public Service Company of New Hampshire | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	38,500	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	9,400	0
Public Service Company of New Hampshire | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 2,800	$ 2,700

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 14,794,900	$ 14,410,500
Distribution - Natural Gas	3,371,200	3,244,200
Transmission - Electric	9,733,600	9,270,900
Distribution - Water	1,594,300	1,558,400
Solar	109,300	36,200
Utility	29,603,300	28,520,200
Other	759,000	693,700
Property, Plant and Equipment, Gross	30,362,300	29,213,900
Less: Accumulated Depreciation
Utility	(7,065,400)	(6,846,900)
Other	(325,400)	(286,900)
Total Accumulated Depreciation	(7,390,800)	(7,133,800)
Property, Plant and Equipment, Net	22,971,500	22,080,100
Construction Work in Progress	1,996,200	1,537,400
Net Plant	24,967,702	23,617,463
The Connecticut Light and Power Company
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	6,027,100	5,888,300
Transmission - Electric	4,513,700	4,239,900
Solar	0	0
Property, Plant and Equipment, Gross	10,540,800	10,128,200
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,297,400)	(2,239,000)
Property, Plant and Equipment, Net	8,243,400	7,889,200
Construction Work in Progress	510,300	381,800
Net Plant	8,753,744	8,271,030
NSTAR Electric Company
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	6,651,100	6,479,000
Transmission - Electric	3,915,500	3,821,200
Solar	109,300	36,200
Property, Plant and Equipment, Gross	10,675,900	10,336,400
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,673,000)	(2,550,200)
Property, Plant and Equipment, Net	8,002,900	7,786,200
Construction Work in Progress	573,200	460,300
Net Plant	8,576,096	8,246,494
Public Service Company of New Hampshire
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	2,157,000	2,083,400
Transmission - Electric	1,255,600	1,161,300
Solar	0	0
Property, Plant and Equipment, Gross	3,412,600	3,244,700
Less: Accumulated Depreciation
Total Accumulated Depreciation	(762,100)	(751,800)
Property, Plant and Equipment, Net	2,650,500	2,492,900
Construction Work in Progress	176,000	149,400
Net Plant	$ 2,826,541	$ 2,642,274

DERIVATIVE INSTRUMENTS - Gross

DERIVATIVE INSTRUMENTS - Gross Fair Value of Contracts (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Derivative Assets | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	$ 0.8	$ 0
Netting	(0.5)	0
Net Amount Recorded as a Derivative	0.3	0
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	8.8	9.5
Netting	(4.8)	(7.1)
Net Amount Recorded as a Derivative	4	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	75	71.9
Netting	(2.3)	(5.3)
Net Amount Recorded as a Derivative	72.7	66.6
Current Derivative Liabilities | Level 2
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	0	(4.5)
Netting	0	0
Net Amount Recorded as a Derivative	0	(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	(50.8)	(54.4)
Netting	0	0
Net Amount Recorded as a Derivative	(50.8)	(54.4)
Long-Term Derivative Liabilities | Level 2
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(0.1)	(0.4)
Netting	0	0
Net Amount Recorded as a Derivative	(0.1)	(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	(385.8)	(376.9)
Netting	0	0
Net Amount Recorded as a Derivative	$ (385.8)	$ (376.9)

DERIVATIVE INSTRUMENTS - Deriva

DERIVATIVE INSTRUMENTS - Derivative Contracts at Fair Value (Details) MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)MMBTUMWhMW	Sep. 30, 2017USD ($)	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 (in MW) | MW			787
Amount of natural gas to be purchased under futures contracts | MMBTU			10.6		9.5
Gains (losses) on deferred as regulatory costs | $	$ 1.6	$ 0.6	$ (25.8)	$ (30.3)
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 (mwh) | MWh			0.1

DERIVATIVE INSTRUMENTS - Unobse

DERIVATIVE INSTRUMENTS - Unobservable Inputs Utilized (Details) - The Connecticut Light and Power Company - Level 3 - $ / KWmo	Sep. 30, 2018	Dec. 31, 2017
Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Capacity Prices (in USD per kilowatt month)	4.30	5
Forward Reserve (in USD per kilowatt month)	0.95	1
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Capacity Prices (in USD per kilowatt month)	7.44	8.70
Forward Reserve (in USD per kilowatt month)	2	2

DERIVATIVE INSTRUMENTS - Unob_2

DERIVATIVE INSTRUMENTS - Unobservable Inputs Narrative (Details) - Level 3	9 Months Ended
	Sep. 30, 2018
Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	1.00%
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	16.00%

DERIVATIVE INSTRUMENTS - Deri_2

DERIVATIVE INSTRUMENTS - Derivative Assets and Liabilities Measured at Fair Value (Details) - The Connecticut Light and Power Company - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	$ (369.3)	$ (394.8)	$ (362.3)	$ (420.5)
Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities	1.2	(0.7)	(27)	(15.9)
Settlements	8.2	13.9	29.4	54.8
Fair Value as of End of Period	$ (359.9)	$ (381.6)	$ (359.9)	$ (381.6)

MARKETABLE SECURITIES - Securit

MARKETABLE SECURITIES - Securities Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities	$ 54.5	$ 54.5	$ 50
Unrealized losses recorded in other income	2.4	2.6
CYAPC
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities	258	258
Marketable securities held in nuclear decommissioning trust	$ 247.1	$ 247.1	242.3
YAEC
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities			$ 263.8

MARKETABLE SECURITIES - Schedul

MARKETABLE SECURITIES - Schedule of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Total Debt Securities	$ 292.8	$ 284.9
Pre-Tax Unrealized Gains	0.8	3.2
Pre-Tax Unrealized Losses	(2.7)	(1.1)
Fair Value	$ 290.9	$ 287

MARKETABLE SECURITIES - Sched_2

MARKETABLE SECURITIES - Schedule of Contractual Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Amortized Cost
Less than one year	$ 28.5
One to five years	48.7
Six to ten years	61.8
Greater than ten years	153.8
Total Debt Securities	292.8	$ 284.9
Fair Value
Less than one year	28.5
One to five years	48.3
Six to ten years	61.2
Greater than ten years	152.9
Total Debt Securities	$ 290.9	$ 287

MARKETABLE SECURITIES - Sched_3

MARKETABLE SECURITIES - Schedule of Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 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	$ 603.4	$ 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	333.4	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	312.5	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	20.9	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	270	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	80.8	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	41.8	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	14.3	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	121.2	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	$ 11.9	$ 10.7

SHORT-TERM AND LONG-TERM DEBT -

SHORT-TERM AND LONG-TERM DEBT - Narrative (Details)	Oct. 10, 2018USD ($)	Jan. 31, 2018USD ($)issuance	Sep. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Line of Credit Facility [Line Items]
Notes payable to Eversource parent			$ 196,900,000	$ 115,900,000
Long-term debt, current maturities			387,310,000	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			826,700,000	979,300,000
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			$ 16,000,000	198,000,000
NSTAR Electric Company | Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity			650,000,000
Short-term debt			240,500,000	234,000,000
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 Facility [Line Items]
Notes payable to Eversource parent			$ 108,000,000
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			45,900,000	69,500,000
Long-term debt, current maturities			250,000,000	300,000,000
Public Service Company of New Hampshire
Line of Credit Facility [Line Items]
Notes payable to Eversource parent			46,600,000	262,900,000
Long-term debt, current maturities			0	$ 110,000,000
NSTAR Gas
Line of Credit Facility [Line Items]
Notes payable to Eversource parent			$ 117,200,000
2001 Series A Pollution Control Revenue Bonds | Subsequent Event | Public Service Company of New Hampshire
Line of Credit Facility [Line Items]
Extinguishment of Debt, Amount	$ 89,300,000

SHORT-TERM AND LONG-TERM DEBT_2

SHORT-TERM AND LONG-TERM DEBT - Schedule of Commercial Paper Program (Details) - Commercial Paper - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
NSTAR Electric Company
Debt Instrument [Line Items]
Borrowings Outstanding	$ 240.5	$ 234
Available Borrowing Capacity	$ 409.5	$ 416
Weighted-Average Interest Rate	2.17%	1.55%
Eversource Parent
Debt Instrument [Line Items]
Borrowings Outstanding	$ 826.7	$ 979.3
Available Borrowing Capacity	$ 623.3	$ 470.7
Weighted-Average Interest Rate	2.34%	1.86%

SHORT-TERM AND LONG-TERM DEBT_3

SHORT-TERM AND LONG-TERM DEBT - Schedule of Issuances and Repayments (Details) - USD ($)	1 Months Ended				9 Months Ended
	Oct. 31, 2018	Jan. 31, 2015	May 31, 2013	May 31, 2008	Sep. 30, 2018	Sep. 30, 2017	Jan. 31, 2018
Debt Instrument [Line Items]
Repayments					$ (860,855,000)	$ (320,000,000)
Senior Notes | Series O First Mortgage Bonds
Debt Instrument [Line Items]
Issuances					50,000,000
Senior Notes | Series P First Mortgage Bonds
Debt Instrument [Line Items]
Issuances					100,000,000
The Connecticut Light and Power Company
Debt Instrument [Line Items]
Repayments					(300,000,000)	(250,000,000)
The Connecticut Light and Power Company | Senior Notes | 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
Debt Instrument [Line Items]
Repayments				$ (300,000,000)
Interest rate, stated percentage				5.65%
Public Service Company of New Hampshire
Debt Instrument [Line Items]
Repayments					$ (110,000,000)	$ (70,000,000)
Public Service Company of New Hampshire | Senior Notes | 2008 Series O First Mortgage Bonds
Debt Instrument [Line Items]
Repayments				$ (110,000,000)
Interest rate, stated percentage				6.00%
Eversource Parent | Senior Notes | Eversource Parent 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 | Series M Senior Notes
Debt Instrument [Line Items]
Issuances							$ 450,000,000
Interest rate, stated percentage							3.30%
Eversource Parent | Senior Notes | 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
Debt Instrument [Line Items]
Repayments			$ (300,000,000)
Interest rate, stated percentage			1.45%
Eversource Parent | Senior Notes | Series O First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage			4.13%
Eversource Parent | Senior Notes | Series P First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage					4.09%
Subsequent Event | Senior Notes | Series J Senior Notes Due 2018
Debt Instrument [Line Items]
Repayments	$ (100,000,000)
Interest rate, stated percentage	6.90%

RATE REDUCTION BONDS AND VARI_3

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Narrative (Details) - Public Service Company of New Hampshire - Rate Reduction Bonds $ in Millions	May 08, 2018USD ($)
Debt Instrument [Line Items]
Amount of securitized rate reduction bonds issued	$ 635.7
Weighted average interest rate	3.66%

RATE REDUCTION BONDS AND VARI_4

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	$ 5,153,300	$ 5,239,300
Accrued Interest (included in Other Current Liabilities)	616,662	594,176
Rate Reduction Bonds - Current Portion	52,332	0
Rate Reduction Bonds - Long-Term Portion	583,331	0
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	618,600	0
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	169,200	137,400
Public Service Company of New Hampshire
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	953,500	940,800
Accrued Interest (included in Other Current Liabilities)	34,790	33,437
Rate Reduction Bonds - Current Portion	52,332	0
Rate Reduction Bonds - Long-Term Portion	583,331	0
Public Service Company of New Hampshire | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	618,600	0
Public Service Company of New Hampshire | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	12,400	$ 15,800
Variable Interest Entity, Primary Beneficiary | Public Service Company of New Hampshire
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash - Current Portion (included in Prepayments and Other Current Assets)	26,900
Restricted Cash - Long-Term Portion (included in Other Long-Term Assets)	3,200
Accrued Interest (included in Other Current Liabilities)	8,800
Rate Reduction Bonds - Current Portion	52,300
Rate Reduction Bonds - Long-Term Portion	583,300
Variable Interest Entity, Primary Beneficiary | Public Service Company of New Hampshire | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory assets	$ 1,000

RATE REDUCTION BONDS AND VARI_5

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 125,201	$ 108,719	$ 372,734	$ 319,477
Public Service Company of New Hampshire
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	16,593	$ 12,896	43,977	$ 38,676
Variable Interest Entity, Primary Beneficiary | Rate Reduction Bonds | Public Service Company of New Hampshire
Condensed Income Statements, Captions [Line Items]
Amortization of Regulatory Assets, Net	10,200		17,100
Interest Expense on RRB Principal (included in Interest Expense)	$ 6,000		$ 8,800

PENSION BENEFITS AND POSTRETI_3

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 20.9	$ 17.4	$ 64.2	$ 53.8
Interest Cost	49.2	47.2	147.1	140.7
Expected Return on Plan Assets	(97.8)	(83.5)	(293.8)	(250.5)
Actuarial Loss	35.7	33.9	107.6	101.3
Prior Service Cost/(Credit)	2	1.2	6	3.4
Total Net Periodic Benefit Expense/(Income)	10	16.2	31.1	48.7
Capitalized Pension Expense/(Income)	6.6	5.5	20.2	16.5
PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.5	2.4	7.5	7.1
Interest Cost	7.7	6.8	23	20.3
Expected Return on Plan Assets	(18.2)	(16)	(54.2)	(47.8)
Actuarial Loss	2.6	2.2	7.7	6.9
Prior Service Cost/(Credit)	(6)	(5.3)	(17.6)	(16.1)
Total Net Periodic Benefit Expense/(Income)	(11.4)	(9.9)	(33.6)	(29.6)
Capitalized Pension Expense/(Income)	0.7	(4.8)	2.3	(14.3)
The Connecticut Light and Power Company | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	5.2	4.6	16.2	13.9
Interest Cost	10.5	10.5	31.4	31.3
Expected Return on Plan Assets	(19.4)	(17.8)	(59.7)	(53.9)
Actuarial Loss	7.1	6.8	21.9	20.7
Prior Service Cost/(Credit)	0.2	0.4	0.8	1.1
Total Net Periodic Benefit Expense/(Income)	3.6	4.5	10.6	13.1
Intercompany Allocations	1.5	2.4	4.5	7.4
Capitalized Pension Expense/(Income)	2	2.4	6.2	7.3
The Connecticut Light and Power Company | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.4	0.5	1.4	1.5
Interest Cost	1.5	1.3	4.4	4
Expected Return on Plan Assets	(2.6)	(2.4)	(7.8)	(7.3)
Actuarial Loss	0.4	0.2	1.2	0.7
Prior Service Cost/(Credit)	0.3	0.3	0.8	0.8
Total Net Periodic Benefit Expense/(Income)	0	(0.1)	0	(0.3)
Intercompany Allocations	(0.3)	(0.2)	(0.8)	(0.5)
Capitalized Pension Expense/(Income)	0.1	(0.1)	0.5	(0.4)
NSTAR Electric Company | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	4.3	3.8	13.1	11.7
Interest Cost	10.9	10.7	32.6	31.9
Expected Return on Plan Assets	(26.6)	(21.9)	(78.3)	(65.8)
Actuarial Loss	10.1	10.4	31	30.9
Prior Service Cost/(Credit)	0.1	0.2	0.2	0.4
Total Net Periodic Benefit Expense/(Income)	(1.2)	3.2	(1.4)	9.1
Intercompany Allocations	1.6	2.3	4.8	6.9
Capitalized Pension Expense/(Income)	1.8	2	5.8	5.7
NSTAR Electric Company | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.5	0.4	1.6	1.4
Interest Cost	2.2	2.2	6.5	6.5
Expected Return on Plan Assets	(8.1)	(7.2)	(24.4)	(21.6)
Actuarial Loss	0.5	0.9	1.7	2.6
Prior Service Cost/(Credit)	(4.3)	(4.3)	(12.7)	(12.8)
Total Net Periodic Benefit Expense/(Income)	(9.2)	(8)	(27.3)	(23.9)
Intercompany Allocations	(0.3)	(0.2)	(1)	(0.8)
Capitalized Pension Expense/(Income)	0.2	(4.1)	0.7	(12.1)
Public Service Company of New Hampshire | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.7	2.4	8.4	7.3
Interest Cost	5.5	5.3	16.4	15.9
Expected Return on Plan Assets	(10.8)	(10)	(32.6)	(29.9)
Actuarial Loss	3.3	3	9.8	8.7
Prior Service Cost/(Credit)	0.1	0.1	0.2	0.4
Total Net Periodic Benefit Expense/(Income)	0.8	0.8	2.2	2.4
Intercompany Allocations	0.5	0.8	1.4	2.5
Capitalized Pension Expense/(Income)	0.8	0.4	2.3	1.1
Public Service Company of New Hampshire | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.3	0.3	0.9	1
Interest Cost	0.9	0.8	2.5	2.3
Expected Return on Plan Assets	(1.5)	(1.4)	(4.5)	(4.1)
Actuarial Loss	0.2	0.1	0.6	0.4
Prior Service Cost/(Credit)	0.1	0.2	0.4	0.4
Total Net Periodic Benefit Expense/(Income)	0	0	(0.1)	0
Intercompany Allocations	(0.1)	(0.1)	(0.3)	(0.3)
Capitalized Pension Expense/(Income)	$ 0.1	$ 0	$ 0.3	$ 0

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Schedule of Environmental Matters (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018USD ($)site	Dec. 31, 2017USD ($)site
Site Contingency [Line Items]
Number of Sites | site	60	59
Reserve | $	$ 66.6	$ 54.9
The Connecticut Light and Power Company
Site Contingency [Line Items]
Number of Sites | site	14	14
Reserve | $	$ 5	$ 4.7
NSTAR Electric Company
Site Contingency [Line Items]
Number of Sites | site	17	15
Reserve | $	$ 10.9	$ 2.7
Public Service Company of New Hampshire
Site Contingency [Line Items]
Number of Sites | site	9	10
Reserve | $	$ 5.5	$ 5.7

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Environmental Matters Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Site Contingency [Line Items]
Reserve	$ 66.6	$ 54.9
MGP Site accrual
Site Contingency [Line Items]
Reserve	$ 52.3	$ 49

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Guarantees and Indemnifications Narrative (Details)	Sep. 30, 2018USD ($)
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 CONTINGENCIES_4

COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) $ in Millions	Sep. 30, 2018USD ($)
Eversource Gas Transmission LLC
Loss Contingencies [Line Items]
Maximum Exposure	$ 184.9
Various
Loss Contingencies [Line Items]
Maximum Exposure	42.7
Eversource Service and Rocky River Realty Company
Loss Contingencies [Line Items]
Maximum Exposure	$ 6.6

COMMITMENTS AND CONTINGENCIES_5

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 CONTINGENCIES_6

COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) - USD ($) $ in Millions	Apr. 29, 2016	Oct. 16, 2014	Sep. 30, 2018	Jul. 28, 2017	Mar. 26, 2014	Dec. 31, 2012	Oct. 15, 2014
Loss Contingencies [Line Items]
Percentage of base ROE reasonably justified			10.41%
Percentage of incentive cap on total ROE			13.08%
FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Base ROE subsequently authorized			11.14%
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%
Maximum percentage cap of ROE for incentive projects	11.74%
Loss contingency, estimate of possible earnings impact			0
Base ROE subsequently authorized				10.57%
FERC ROE First Complaint
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project		11.74%
Loss contingency, estimate of possible earnings impact			0
Base ROE subsequently authorized		10.57%				10.57%
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
Minimum
Loss Contingencies [Line Items]
Percentage of base ROE reasonably justified			9.60%
Minimum | FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project							11.14%
Maximum
Loss Contingencies [Line Items]
Percentage of base ROE reasonably justified			10.99%
Maximum | FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project							13.10%

COMMITMENTS AND CONTINGENCIES_7

COMMITMENTS AND CONTINGENCIES - Schedule of Complaints and Base ROEs (Details) - USD ($) $ in Millions	Apr. 29, 2016	Oct. 16, 2014	Sep. 30, 2018	Jul. 28, 2017	Mar. 26, 2014	Dec. 31, 2012	Oct. 30, 2015	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 September 30, 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 September 30, 2018 (in millions)			39.1
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 September 30, 2018 (in millions)			0
FERC ROE Fourth Complaint
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)				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 September 30, 2018 (in millions)			$ 0
Base ROE percentage of complaint period	10.57%
FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (as a percentage)			11.14%
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 September 30, 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 September 30, 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 September 30, 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 CONTINGENCIES_8

COMMITMENTS AND CONTINGENCIES - Harbor Civil Action (Details) $ in Millions	Jul. 15, 2016MW	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

ASSETS HELD FOR SALE - Narrativ

ASSETS HELD FOR SALE - Narrative (Details) $ in Thousands	Jul. 16, 2018USD ($)license	Jan. 10, 2018USD ($)	Oct. 31, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	May 08, 2018USD ($)	Dec. 31, 2017USD ($)
Regulatory Assets [Line Items]
Proceeds from sale of property						$ 193,924	$ 0
Regulatory assets held for sale				$ 5,153,300		5,153,300			$ 5,239,300
Pre-tax income associated with assets held for sale				357,538	$ 415,068	1,027,829	1,204,137
Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Thermal generation assets			$ 175,000	17,300
Purchase price in purchase sale agreement		$ 40,900
Proceeds from purchase and sale agreement	$ 77,300	$ 134,100
Proceeds from sale of property				116,800		193,924	0
Number of licenses | license	6
Hydroelectric assets	$ 5,700		$ 83,000
Regulatory assets held for sale				953,500		953,500			940,800
Difference between book value of hydroelectric generation assets and expected proceeds from sale						17,200
Pre-tax income associated with assets held for sale				55,975	55,735	139,394	164,754
Deferred Costs from Generation Asset Sale
Regulatory Assets [Line Items]
Regulatory assets held for sale				0		0			516,100
Deferred Costs from Generation Asset Sale | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Regulatory assets held for sale				0		0			$ 516,100
Domestic Tax Authority | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Pre-tax income associated with assets held for sale				$ 700	$ 14,600	$ 9,900	$ 44,700
Rate Reduction Bonds | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Amount of securitized rate reduction bonds issued								$ 635,700

ASSETS HELD FOR SALE - Generati

ASSETS HELD FOR SALE - Generation Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Accumulated Depreciation	$ (7,390,800)	$ (7,133,800)
Net Plant	24,967,702	23,617,463
Other Assets	759,000	693,700
Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Accumulated Depreciation	(762,100)	(751,800)
Net Plant	$ 2,826,541	2,642,274
Electricity Generation Plant, Non-Nuclear | Public Service Company of New Hampshire
Regulatory Assets [Line Items]
Thermal Gross Plant		1,091,400
Hydroelectric Gross Plant		83,000
Accumulated Depreciation		(575,400)
Net Plant		599,000
Fuel and Inventory		87,700
Materials and Supplies		27,300
Emissions Allowances		19,100
Other Assets		2,600
Deferred Costs from Thermal Generation Asset Sale		(516,100)
Total Generation Assets Held for Sale		$ 219,600

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 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
Rate Reduction Bonds	583,331	0
Carrying Amount
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	12,538,800	12,325,500
Rate Reduction Bonds	635,700
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	163,000	160,800
Long-Term Debt	12,517,400	12,877,100
Rate Reduction Bonds	631,300
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
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	3,253,600	3,059,100
Rate Reduction Bonds	0
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	120,200	116,500
Long-Term Debt	3,420,400	3,430,500
Rate Reduction Bonds	0
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
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	2,944,600	2,943,800
Rate Reduction Bonds	0
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	42,800	44,300
Long-Term Debt	2,990,000	3,156,500
Rate Reduction Bonds	0
Public Service Company of New Hampshire
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Rate Reduction Bonds	583,331	0
Public Service Company of New Hampshire | Carrying Amount
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	894,100	1,002,400
Rate Reduction Bonds	635,700
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	904,300	$ 1,038,200
Rate Reduction Bonds	$ 631,300

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent [Roll Forward]
OCI Before Reclassifications			$ 1,900	$ (2,800)
Amounts Reclassified from AOCI			4,900	4,500
Net OCI	$ 1,406	$ (680)	6,821	1,667
Total
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(66,400)	(65,300)
Ending balance	(59,600)	(63,600)	(59,600)	(63,600)
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			1,600	1,600
Net OCI			1,600	1,600
Ending balance	(4,600)	(6,600)	(4,600)	(6,600)
Unrealized Losses on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance			0	400
OCI Before Reclassifications			(700)	700
Amounts Reclassified from AOCI			0	0
Net OCI			(700)	700
Ending balance	(700)	1,100	(700)	1,100
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance			(60,200)	(57,500)
OCI Before Reclassifications			2,600	(3,500)
Amounts Reclassified from AOCI			3,300	2,900
Net OCI			5,900	(600)
Ending balance	$ (54,300)	$ (58,100)	$ (54,300)	$ (58,100)

COMMON SHAREHOLDERS' EQUITY A_2

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Equity [Abstract]
Net income attributable to noncontrolling interests	$ 1,900	$ 1,900	$ 5,600	$ 5,600
Noncontrolling Interest – Preferred Stock of Subsidiaries	$ 155,570		$ 155,570		$ 155,570

COMMON SHARES (Details)

COMMON SHARES (Details) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 5
Authorized (in shares)	380,000,000
Issued (in shares)	333,878,402	333,878,402
Treasury stock (in shares)	16,992,594	16,992,594
Common stock outstanding (in shares)	316,885,808	316,885,808
The Connecticut Light and Power Company
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 10
Authorized (in shares)	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
Authorized (in shares)	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
Authorized (in shares)	100,000,000
Issued (in shares)	301	301

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 289,380	$ 260,370	$ 801,693	$ 750,577
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,360,110	317,393,029	317,367,252	317,415,848
Dilutive Effect (in shares)	607,201	556,367	581,246	591,194
Diluted (in shares)	317,967,311	317,949,396	317,948,498	318,007,042
Basic EPS (in dollars per share)	$ 0.91	$ 0.82	$ 2.53	$ 2.36
Diluted EPS (in dollars per share)	$ 0.91	$ 0.82	$ 2.52	$ 2.36

REVENUES (Details)

REVENUES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	$ 2,321,100		$ 6,458,900
Operating Revenues	2,271,425	$ 1,988,512	6,413,243	$ 5,856,458
Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,195,700		3,397,200
Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	847,100		2,312,900
Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	116,300		336,400
Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	2,159,100		6,046,500
Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	76,000		196,400
Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	61,500		185,900
Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	24,100		66,100
Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	400		(36,000)
Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(55,200)		(60,500)
Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	5,500		14,800
The Connecticut Light and Power Company
Disaggregation of Revenue [Line Items]
Operating Revenues	865,028	774,762	2,344,903	2,173,629
NSTAR Electric Company
Disaggregation of Revenue [Line Items]
Operating Revenues	939,460	851,922	2,400,324	2,290,432
Public Service Company of New Hampshire
Disaggregation of Revenue [Line Items]
Operating Revenues	290,203	250,032	792,700	733,572
Operating Segments | Electric Distribution
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	2,074,200		5,366,600
Operating Revenues	2,027,400	1,547,100	5,321,800	4,224,200
Operating Segments | Electric Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,111,700		2,900,400
Operating Segments | Electric Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	789,600		2,023,000
Operating Segments | Electric Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	98,700		268,600
Operating Segments | Electric Distribution | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	2,000,000		5,192,000
Operating Segments | Electric Distribution | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Distribution | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	48,800		141,400
Operating Segments | Electric Distribution | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	20,200		54,400
Operating Segments | Electric Distribution | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	5,200		(21,200)
Operating Segments | Electric Distribution | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(51,600)		(57,200)
Operating Segments | Electric Distribution | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	4,800		12,400
Operating Segments | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	109,900		741,700
Operating Revenues	109,000	109,200	740,500	698,800
Operating Segments | Natural Gas Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	42,800		395,900
Operating Segments | Natural Gas Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	40,800		245,400
Operating Segments | Natural Gas Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	18,900		71,900
Operating Segments | Natural Gas Distribution | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	102,500		713,200
Operating Segments | Natural Gas Distribution | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Natural Gas Distribution | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	11,400		41,400
Operating Segments | Natural Gas Distribution | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(500)		(1,400)
Operating Segments | Natural Gas Distribution | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(3,500)		(11,500)
Operating Segments | Natural Gas Distribution | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(1,500)		(3,200)
Operating Segments | Natural Gas Distribution | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	600		2,000
Operating Segments | Electric Transmission
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	367,600		998,300
Operating Revenues	330,600	328,500	953,000	970,000
Operating Segments | Electric Transmission | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Transmission | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Transmission | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Transmission | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Transmission | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	364,500		988,900
Operating Segments | Electric Transmission | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Transmission | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	3,100		9,400
Operating Segments | Electric Transmission | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Electric Transmission | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(37,000)		(45,300)
Operating Segments | Electric Transmission | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0		0
Operating Segments | Water Distribution
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	62,300		157,400
Operating Revenues	63,500	0	161,500	0
Operating Segments | Water Distribution | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	41,200		100,900
Operating Segments | Water Distribution | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	17,900		47,900
Operating Segments | Water Distribution | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,300		3,400
Operating Segments | Water Distribution | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	60,400		152,200
Operating Segments | Water Distribution | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Water Distribution | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,300		3,100
Operating Segments | Water Distribution | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,900		5,400
Operating Segments | Water Distribution | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(1,300)		(3,300)
Operating Segments | Water Distribution | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	1,100		3,700
Operating Segments | Water Distribution | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	100		400
Operating Segments | Other
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	224,600		692,500
Operating Revenues	224,600		692,500
Operating Segments | Other | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Other | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Other | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Other | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Other | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	11,700		34,400
Operating Segments | Other | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Other | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	212,900		658,100
Operating Segments | Other | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Operating Segments | Other | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0		0
Operating Segments | Other | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0		0
Operating Segments | The Connecticut Light and Power Company
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,048,000		2,744,800
Operating Segments | The Connecticut Light and Power Company | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	539,600		1,410,000
Operating Segments | The Connecticut Light and Power Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	259,000		702,200
Operating Segments | The Connecticut Light and Power Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	39,400		111,800
Operating Segments | The Connecticut Light and Power Company | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	838,000		2,224,000
Operating Segments | The Connecticut Light and Power Company | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	179,100		469,800
Operating Segments | The Connecticut Light and Power Company | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	13,300		34,300
Operating Segments | The Connecticut Light and Power Company | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	9,300		25,000
Operating Segments | The Connecticut Light and Power Company | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	8,300		(8,300)
Operating Segments | NSTAR Electric Company
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	1,053,300		2,700,600
Operating Segments | NSTAR Electric Company | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	414,800		1,071,600
Operating Segments | NSTAR Electric Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	443,800		1,083,800
Operating Segments | NSTAR Electric Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	38,000		96,900
Operating Segments | NSTAR Electric Company | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	896,600		2,252,300
Operating Segments | NSTAR Electric Company | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	128,300		367,700
Operating Segments | NSTAR Electric Company | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	18,100		56,400
Operating Segments | NSTAR Electric Company | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	10,300		27,900
Operating Segments | NSTAR Electric Company | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		(3,700)
Operating Segments | Public Service Company of New Hampshire
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	341,300		923,000
Operating Segments | Public Service Company of New Hampshire | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	157,300		418,800
Operating Segments | Public Service Company of New Hampshire | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	87,300		238,400
Operating Segments | Public Service Company of New Hampshire | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	21,300		59,900
Operating Segments | Public Service Company of New Hampshire | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	265,900		717,100
Operating Segments | Public Service Company of New Hampshire | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	57,100		151,400
Operating Segments | Public Service Company of New Hampshire | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	17,400		52,300
Operating Segments | Public Service Company of New Hampshire | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	4,000		11,400
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)		(9,200)
Segment Reconciling Items [Member] | The Connecticut Light and Power Company | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(64,300)		(68,400)
Segment Reconciling Items [Member] | The Connecticut Light and Power Company | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	2,800		6,500
Segment Reconciling Items [Member] | NSTAR Electric Company | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(15,400)		(15,600)
Segment Reconciling Items [Member] | NSTAR Electric Company | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	1,800		5,100
Segment Reconciling Items [Member] | Public Service Company of New Hampshire | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	(8,900)		(18,500)
Segment Reconciling Items [Member] | Public Service Company of New Hampshire | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	200		800
Eliminations
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(517,500)		(1,497,600)
Operating Revenues	(483,700)	$ (220,500)	(1,456,100)	$ (714,000)
Eliminations | Residential
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Eliminations | Commercial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(1,200)		(3,400)
Eliminations | Industrial
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(2,600)		(7,500)
Eliminations | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(3,800)		(10,900)
Eliminations | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(300,200)		(826,900)
Eliminations | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Eliminations | Other Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	(213,500)		(659,800)
Eliminations | Reserve for Revenue Subject to Refund
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	0		0
Eliminations | Alternative Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	33,800		41,500
Eliminations | Other Revenue
Disaggregation of Revenue [Line Items]
Operating Revenues	0		0
Consolidations Eliminations | The Connecticut Light and Power Company
Disaggregation of Revenue [Line Items]
Operating Revenues	(121,500)		(338,000)
Consolidations Eliminations | NSTAR Electric Company
Disaggregation of Revenue [Line Items]
Operating Revenues	(100,200)		(289,800)
Consolidations Eliminations | Public Service Company of New Hampshire
Disaggregation of Revenue [Line Items]
Operating Revenues	$ (42,400)		$ (112,600)

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)segmentcompany	Sep. 30, 2017USD ($)
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	$ 842,291	$ 651,776	$ 2,442,953	$ 1,955,129
The Connecticut Light and Power Company
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased from Enbridge by Yankee Gas and NSTAR Gas	314,571	259,005	$ 850,794	711,154
Number of reportable segments | segment			1
NSTAR Electric Company
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased from Enbridge by Yankee Gas and NSTAR Gas	383,208	294,115	$ 981,895	799,007
Number of reportable segments | segment			1
Public Service Company of New Hampshire
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased from Enbridge by Yankee Gas and NSTAR Gas	$ 100,763	$ 57,099	$ 293,975	$ 179,289
Number of reportable segments | segment			1
Affiliated Entity
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased from Enbridge by Yankee Gas and NSTAR Gas			$ 62,500

SEGMENT INFORMATION - Schedule

SEGMENT INFORMATION - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,271,425	$ 1,988,512	$ 6,413,243	$ 5,856,458
Depreciation and Amortization	(301,400)	(236,300)	(786,200)	(629,200)
Other Operating Expenses	(1,504,000)	(1,256,900)	(4,327,100)	(3,782,900)
Operating Income/(Loss)	466,021	495,251	1,299,907	1,444,436
Interest Expense	(125,200)	(108,700)	(372,700)	(319,500)
Other Income/(Loss), Net	16,718	28,536	100,656	79,178
Net Income Attributable to Common Shareholders	289,380	260,370	801,693	750,577
Cash Flows Used for Investments in Plant			1,885,081	1,642,280
Assets	37,515,669		37,515,669		$ 36,220,386
Operating Segments | Electric Distribution
Segment Reporting Information [Line Items]
Operating Revenues	2,027,400	1,547,100	5,321,800	4,224,200
Depreciation and Amortization	(206,100)	(159,600)	(486,000)	(394,900)
Other Operating Expenses	(1,562,200)	(1,095,200)	(4,238,600)	(3,076,100)
Operating Income/(Loss)	259,100	292,300	597,200	753,200
Interest Expense	(52,400)	(51,300)	(152,000)	(149,000)
Other Income/(Loss), Net	32,200	14,200	70,900	35,300
Net Income Attributable to Common Shareholders	173,800	157,400	379,300	393,400
Cash Flows Used for Investments in Plant			717,400	752,400
Assets	21,189,000		21,189,000		19,250,400
Operating Segments | Natural Gas Distribution
Segment Reporting Information [Line Items]
Operating Revenues	109,000	109,200	740,500	698,800
Depreciation and Amortization	(13,900)	(15,200)	(59,600)	(54,800)
Other Operating Expenses	(102,400)	(96,200)	(585,700)	(537,300)
Operating Income/(Loss)	(7,300)	(2,200)	95,200	106,700
Interest Expense	(11,300)	(10,800)	(33,700)	(32,300)
Other Income/(Loss), Net	1,500	1,000	5,100	2,900
Net Income Attributable to Common Shareholders	(12,600)	(6,200)	50,200	49,100
Cash Flows Used for Investments in Plant			245,500	209,800
Assets	3,747,400		3,747,400		3,595,200
Operating Segments | Electric Transmission
Segment Reporting Information [Line Items]
Operating Revenues	330,600	328,500	953,000	970,000
Depreciation and Amortization	(58,300)	(52,600)	(171,800)	(154,500)
Other Operating Expenses	(96,700)	(95,500)	(268,700)	(280,600)
Operating Income/(Loss)	175,600	180,400	512,500	534,900
Interest Expense	(30,300)	(29,200)	(89,900)	(86,100)
Other Income/(Loss), Net	9,000	8,500	26,700	20,300
Net Income Attributable to Common Shareholders	109,500	99,000	329,600	289,600
Cash Flows Used for Investments in Plant			735,800	575,600
Assets	10,077,500		10,077,500		9,401,200
Operating Segments | Water Distribution
Segment Reporting Information [Line Items]
Operating Revenues	63,500	0	161,500	0
Depreciation and Amortization	(11,700)	0	(34,600)	0
Other Operating Expenses	(25,500)	0	(73,900)	0
Operating Income/(Loss)	26,300	0	53,000	0
Interest Expense	(8,500)	0	(25,500)	0
Other Income/(Loss), Net	700	0	(400)	0
Net Income Attributable to Common Shareholders	17,600	0	26,300	0
Cash Flows Used for Investments in Plant			68,100	0
Assets	2,240,300		2,240,300		2,470,000
Operating Segments | Other
Segment Reporting Information [Line Items]
Operating Revenues	224,600	224,200	692,500	677,500
Depreciation and Amortization	(12,000)	(9,500)	(35,900)	(26,700)
Other Operating Expenses	(200,900)	(190,100)	(617,200)	(602,900)
Operating Income/(Loss)	11,700	24,600	39,400	47,900
Interest Expense	(30,500)	(21,800)	(94,800)	(63,100)
Other Income/(Loss), Net	251,700	267,600	913,800	854,400
Net Income Attributable to Common Shareholders	271,100	268,400	905,900	839,500
Cash Flows Used for Investments in Plant			118,300	104,500
Assets	16,979,400		16,979,400		15,933,800
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(483,700)	(220,500)	(1,456,100)	(714,000)
Depreciation and Amortization	600	600	1,700	1,700
Other Operating Expenses	483,700	220,100	1,457,000	714,000
Operating Income/(Loss)	600	200	2,600	1,700
Interest Expense	7,800	4,400	23,200	11,000
Other Income/(Loss), Net	(278,400)	(262,800)	(915,400)	(833,700)
Net Income Attributable to Common Shareholders	(270,000)	$ (258,200)	(889,600)	(821,000)
Cash Flows Used for Investments in Plant			0	$ 0
Assets	$ (16,717,900)		$ (16,717,900)		$ (14,430,200)

ACQUISITION OF AQUARION - Narra

ACQUISITION OF AQUARION - Narrative (Details) - USD ($) $ in Millions	Dec. 04, 2017	Mar. 31, 2018
Aquarion Water Company
Business Acquisition [Line Items]
Consideration transferred	$ 1,675
Payments to acquire businesses	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	Sep. 30, 2018	Dec. 31, 2017	Dec. 04, 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