NSTAR Electric Company PFD 4.25% (NSARP) 10-Q 6 Nov 20 2020 Q3 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	9 Months Ended
	Sep. 30, 2020	Oct. 31, 2020
Document And Entity [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity Registrant Name	EVERSOURCE ENERGY
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	300 Cadwell Drive
Entity Address, City or Town	Springfield
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01104
City Area Code	800
Local Phone Number	286-5000
Entity File Number	1-5324
Entity Tax Identification Number	04-2147929
Title of 12(b) Security	Common Shares, $5.00 par value per share
Trading Symbol	ES
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		342,824,425
Entity Central Index Key	0000072741
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
The Connecticut Light and Power Company
Document And Entity [Line Items]
Entity Registrant Name	THE CONNECTICUT LIGHT AND POWER COMPANY
Entity Incorporation, State or Country Code	CT
Entity Address, Address Line One	107 Selden Street
Entity Address, City or Town	Berlin
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06037-1616
City Area Code	800
Local Phone Number	286-5000
Entity File Number	0-00404
Entity Tax Identification Number	06-0303850
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		6,035,205
Entity Central Index Key	0000023426
Current Fiscal Year End Date	--12-31
NSTAR Electric Company
Document And Entity [Line Items]
Entity Registrant Name	NSTAR ELECTRIC COMPANY
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	800 Boylston Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02199
City Area Code	800
Local Phone Number	286-5000
Entity File Number	1-02301
Entity Tax Identification Number	04-1278810
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		200
Entity Central Index Key	0000013372
Current Fiscal Year End Date	--12-31
Public Service Company of New Hampshire
Document And Entity [Line Items]
Entity Registrant Name	PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE
Entity Incorporation, State or Country Code	NH
Entity Address, Address Line One	Energy Park
Entity Address, Address Line Two	780 North Commercial Street
Entity Address, City or Town	Manchester
Entity Address, State or Province	NH
Entity Address, Postal Zip Code	03101-1134
City Area Code	800
Local Phone Number	286-5000
Entity File Number	1-6392
Entity Tax Identification Number	02-0181050
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		301
Entity Central Index Key	0000315256
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current Assets:
Cash and Cash Equivalents	$ 729,993	$ 15,432
Receivables, Net (net of allowance for uncollectible accounts)	1,113,495	989,383
Unbilled Revenues	155,961	181,006
Fuel, Materials, Supplies and REC Inventory	214,300	235,471
Regulatory Assets	762,883	651,112
Prepayments and Other Current Assets	243,781	342,135
Total Current Assets	3,220,413	2,414,539
Property, Plant and Equipment, Net	29,092,981	27,585,470
Deferred Debits and Other Assets:
Regulatory Assets	4,883,165	4,863,639
Goodwill	4,403,666	4,427,266
Investments in Unconsolidated Affiliates	903,177	871,633
Marketable Securities	438,839	449,130
Other Long-Term Assets	565,104	512,238
Total Deferred Debits and Other Assets	11,193,951	11,123,906
Total Assets	43,507,345	41,123,915
Current Liabilities:
Notes Payable	60,500	889,084
Long-Term Debt – Current Portion	1,078,186	327,411
Rate Reduction Bonds – Current Portion	43,210	43,210
Accounts Payable	1,222,058	1,147,872
Regulatory Liabilities	464,673	361,152
Other Current Liabilities	765,443	836,834
Total Current Liabilities	3,634,070	3,605,563
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	3,960,672	3,755,777
Regulatory Liabilities	3,711,488	3,658,042
Derivative Liabilities	312,933	338,710
Asset Retirement Obligations	499,859	488,511
Accrued Pension, SERP and PBOP	1,163,229	1,370,245
Other Long-Term Liabilities	856,285	810,553
Total Deferred Credits and Other Liabilities	10,504,466	10,421,838
Long-Term Debt	14,736,310	13,770,828
Rate Reduction Bonds	496,912	540,122
Noncontrolling Interest – Preferred Stock of Subsidiaries	155,570	155,570
Common Shareholders' Equity:
Common Shares	1,789,092	1,729,292
Capital Surplus, Paid In	7,996,976	7,087,768
Retained Earnings	4,535,860	4,177,048
Accumulated Other Comprehensive Income (Loss)	(60,397)	(65,059)
Treasury Stock	(281,514)	(299,055)
Common Shareholders' Equity	13,980,017	12,629,994
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	43,507,345	41,123,915
The Connecticut Light and Power Company
Current Assets:
Cash and Cash Equivalents	8,173	0
Receivables, Net (net of allowance for uncollectible accounts)	473,830	400,927
Accounts Receivable from Affiliated Companies	43,950	24,577
Unbilled Revenues	50,111	56,465
Fuel, Materials, Supplies and REC Inventory	57,744	50,700
Regulatory Assets	273,792	178,607
Prepaid Property Taxes	73,511	22,799
Prepayments and Other Current Assets	63,097	50,385
Total Current Assets	1,044,208	784,460
Property, Plant and Equipment, Net	10,065,346	9,625,765
Deferred Debits and Other Assets:
Regulatory Assets	1,732,739	1,557,261
Other Long-Term Assets	241,663	217,705
Total Deferred Debits and Other Assets	1,974,402	1,774,966
Total Assets	13,083,956	12,185,191
Current Liabilities:
Notes Payable to Eversource Parent	235,900	63,800
Accounts Payable	554,489	374,698
Accounts Payable to Affiliated Companies	107,212	97,793
Obligations to Third Party Suppliers	52,883	56,952
Regulatory Liabilities	164,946	82,763
Derivative Liabilities	69,218	67,804
Other Current Liabilities	131,939	132,339
Total Current Liabilities	1,316,587	876,149
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,350,403	1,244,551
Regulatory Liabilities	1,196,255	1,164,991
Derivative Liabilities	312,933	338,594
Accrued Pension, SERP and PBOP	325,173	391,159
Other Long-Term Liabilities	153,938	147,586
Total Deferred Credits and Other Liabilities	3,338,702	3,286,881
Long-Term Debt	3,518,115	3,518,136
Noncontrolling Interest – Preferred Stock of Subsidiaries	116,200	116,200
Common Shareholders' Equity:
Common Shares	60,352	60,352
Capital Surplus, Paid In	2,660,765	2,535,765
Retained Earnings	2,072,928	1,791,392
Accumulated Other Comprehensive Income (Loss)	307	316
Common Shareholders' Equity	4,794,352	4,387,825
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	13,083,956	12,185,191
NSTAR Electric Company
Current Assets:
Cash and Cash Equivalents	87	52
Receivables, Net (net of allowance for uncollectible accounts)	439,504	346,785
Accounts Receivable from Affiliated Companies	30,599	29,914
Unbilled Revenues	44,936	37,482
Fuel, Materials, Supplies and REC Inventory	96,351	124,060
Regulatory Assets	278,604	285,591
Prepayments and Other Current Assets	17,613	31,150
Total Current Assets	907,694	855,034
Property, Plant and Equipment, Net	9,943,408	9,472,770
Deferred Debits and Other Assets:
Regulatory Assets	1,194,092	1,250,029
Prepaid PBOP	192,579	166,058
Other Long-Term Assets	148,282	144,368
Total Deferred Debits and Other Assets	1,534,953	1,560,455
Total Assets	12,386,055	11,888,259
Current Liabilities:
Notes Payable	60,500	10,500
Notes Payable to Eversource Parent	36,600	30,300
Long-Term Debt – Current Portion	250,000	95,000
Accounts Payable	304,025	363,691
Accounts Payable to Affiliated Companies	84,942	96,307
Obligations to Third Party Suppliers	115,194	108,827
Renewable Portfolio Standards Compliance Obligations	92,000	150,429
Regulatory Liabilities	210,744	209,180
Other Current Liabilities	104,725	71,333
Total Current Liabilities	1,258,730	1,135,567
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,394,072	1,357,265
Regulatory Liabilities	1,534,760	1,516,585
Accrued Pension, SERP and PBOP	84,088	108,243
Other Long-Term Liabilities	353,030	320,629
Total Deferred Credits and Other Liabilities	3,365,950	3,302,722
Long-Term Debt	3,392,836	3,247,086
Noncontrolling Interest – Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,813,442	1,813,442
Retained Earnings	2,511,742	2,346,287
Accumulated Other Comprehensive Income (Loss)	355	155
Common Shareholders' Equity	4,325,539	4,159,884
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	12,386,055	11,888,259
Public Service Company of New Hampshire
Current Assets:
Cash and Cash Equivalents	767	413
Receivables, Net (net of allowance for uncollectible accounts)	121,125	99,934
Accounts Receivable from Affiliated Companies	11,280	6,763
Unbilled Revenues	40,003	48,146
Fuel, Materials, Supplies and REC Inventory	25,258	24,957
Regulatory Assets	103,570	84,053
Special Deposits	19,088	32,513
Prepayments and Other Current Assets	12,819	19,431
Total Current Assets	333,910	316,210
Property, Plant and Equipment, Net	3,319,483	3,129,506
Deferred Debits and Other Assets:
Regulatory Assets	808,784	861,672
Other Long-Term Assets	37,128	43,270
Total Deferred Debits and Other Assets	845,912	904,942
Total Assets	4,499,305	4,350,658
Current Liabilities:
Notes Payable to Eversource Parent	29,100	27,000
Long-Term Debt – Current Portion	282,000	0
Rate Reduction Bonds – Current Portion	43,210	43,210
Accounts Payable	110,150	127,081
Accounts Payable to Affiliated Companies	25,728	37,946
Regulatory Liabilities	61,457	65,766
Accrued Interest	14,690	19,138
Other Current Liabilities	36,182	32,736
Total Current Liabilities	602,517	352,877
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	525,422	506,212
Regulatory Liabilities	406,211	413,381
Accrued Pension, SERP and PBOP	123,609	157,638
Other Long-Term Liabilities	39,320	37,075
Total Deferred Credits and Other Liabilities	1,094,562	1,114,306
Long-Term Debt	816,974	951,620
Rate Reduction Bonds	496,912	540,122
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	903,134	903,134
Retained Earnings	586,090	490,306
Accumulated Other Comprehensive Income (Loss)	(884)	(1,707)
Common Shareholders' Equity	1,488,340	1,391,733
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	$ 4,499,305	$ 4,350,658

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Allowance for uncollectible accounts	$ 294,972	$ 224,821
The Connecticut Light and Power Company
Allowance for uncollectible accounts	150,758	97,348
NSTAR Electric Company
Allowance for uncollectible accounts	76,760	75,406
Public Service Company of New Hampshire
Allowance for uncollectible accounts	$ 13,972	$ 10,497

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Revenues	$ 2,343,642	$ 2,175,797	$ 6,670,497	$ 6,476,084
Operating Expenses:
Purchased Power, Fuel and Transmission	806,254	730,255	2,312,957	2,326,041
Operations and Maintenance	332,031	331,054	1,006,148	994,660
Depreciation	244,453	222,599	721,179	656,632
Amortization	57,515	73,854	130,687	183,760
Energy Efficiency Programs	145,047	136,832	408,794	382,785
Taxes Other Than Income Taxes	197,112	171,965	556,726	537,636
Impairment of Northern Pass Transmission	0	0	0	239,644
Total Operating Expenses	1,782,412	1,666,559	5,136,491	5,321,158
Operating Income/(Loss)	561,230	509,238	1,534,006	1,154,926
Interest Expense	134,066	135,216	403,067	399,654
Other Income, Net	29,218	26,968	83,565	103,818
Income Before Income Tax Expense	456,382	400,990	1,214,504	859,090
Income Tax Expense	108,242	80,226	275,621	194,435
Net Income	348,140	320,764	938,883	664,655
Net Income Attributable to Noncontrolling Interests	1,880	1,880	5,639	5,639
Net Income Attributable to Common Shareholders	$ 346,260	$ 318,884	$ 933,244	$ 659,016
Basic Earnings Per Common Share (in dollars per share)	$ 1.01	$ 0.98	$ 2.77	$ 2.06
Diluted Earnings Per Common Share (in dollars per share)	$ 1.01	$ 0.98	$ 2.76	$ 2.05
Weighted Average Common Shares Outstanding:
Basic (in shares)	343,076,614	324,037,169	337,375,172	320,442,253
Diluted (in shares)	343,773,602	326,008,342	338,424,100	321,570,926
The Connecticut Light and Power Company
Operating Revenues	$ 994,270	$ 853,943	$ 2,711,394	$ 2,444,034
Operating Expenses:
Purchased Power, Fuel and Transmission	399,117	299,017	1,089,232	865,389
Operations and Maintenance	147,487	135,077	417,717	399,065
Depreciation	80,583	76,250	238,735	224,095
Amortization of Regulatory Assets, Net	36,365	30,406	37,215	78,453
Energy Efficiency Programs	41,829	40,129	109,655	86,897
Taxes Other Than Income Taxes	97,715	82,781	260,571	261,244
Total Operating Expenses	803,096	663,660	2,153,125	1,915,143
Operating Income/(Loss)	191,174	190,283	558,269	528,891
Interest Expense	38,369	39,520	114,972	112,274
Other Income, Net	5,917	4,831	16,273	11,564
Income Before Income Tax Expense	158,722	155,594	459,570	428,181
Income Tax Expense	38,625	43,907	103,464	101,219
Net Income	120,097	111,687	356,106	326,962
NSTAR Electric Company
Operating Revenues	875,371	878,669	2,270,174	2,358,174
Operating Expenses:
Purchased Power, Fuel and Transmission	267,375	300,726	702,117	859,227
Operations and Maintenance	131,143	120,917	369,293	342,804
Depreciation	80,366	74,664	238,232	220,303
Amortization of Regulatory Assets, Net	22,527	27,296	69,139	73,064
Energy Efficiency Programs	85,244	84,409	210,666	227,042
Taxes Other Than Income Taxes	54,680	51,266	153,985	144,314
Total Operating Expenses	641,335	659,278	1,743,432	1,866,754
Operating Income/(Loss)	234,036	219,391	526,742	491,420
Interest Expense	31,029	29,322	95,000	85,442
Other Income, Net	12,802	10,735	38,152	32,479
Income Before Income Tax Expense	215,809	200,804	469,894	438,457
Income Tax Expense	50,081	45,864	106,309	99,769
Net Income	165,728	154,940	363,585	338,688
Public Service Company of New Hampshire
Operating Revenues	283,669	280,431	815,261	797,766
Operating Expenses:
Purchased Power, Fuel and Transmission	96,612	101,381	273,311	300,680
Operations and Maintenance	50,657	50,838	151,802	156,197
Depreciation	25,410	23,539	74,494	69,720
Amortization of Regulatory Assets, Net	7,360	20,421	39,034	39,944
Energy Efficiency Programs	11,081	7,300	29,231	20,229
Taxes Other Than Income Taxes	18,174	12,487	58,331	50,523
Total Operating Expenses	209,294	215,966	626,203	637,293
Operating Income/(Loss)	74,375	64,465	189,058	160,473
Interest Expense	14,942	16,378	44,029	44,654
Other Income, Net	4,065	4,634	10,882	14,640
Income Before Income Tax Expense	63,498	52,721	155,911	130,459
Income Tax Expense	16,347	11,842	37,527	29,947
Net Income	$ 47,151	$ 40,879	$ 118,384	$ 100,512

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Income	$ 348,140	$ 320,764	$ 938,883	$ 664,655
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	602	367	1,218	945
Changes in Unrealized (Losses)/Gains on Marketable Securities	(134)	169	295	1,268
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	1,693	1,088	3,149	5,770
Other Comprehensive Income (Loss), Net of Tax	2,161	1,624	4,662	7,983
Comprehensive Income Attributable to Noncontrolling Interests	(1,880)	(1,880)	(5,639)	(5,639)
Comprehensive Income Attributable to Common Shareholders	348,421	320,508	937,906	666,999
The Connecticut Light and Power Company
Net Income	120,097	111,687	356,106	326,962
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	(7)	(7)	(20)	(20)
Changes in Unrealized (Losses)/Gains on Marketable Securities	(4)	6	11	44
Other Comprehensive Income (Loss), Net of Tax	(11)	(1)	(9)	24
Comprehensive Income Attributable to Common Shareholders	120,086	111,686	356,097	326,986
NSTAR Electric Company
Net Income	165,728	154,940	363,585	338,688
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	109	109	327	328
Changes in Unrealized (Losses)/Gains on Marketable Securities	(1)	2	2	12
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	(43)	1	(129)	3
Other Comprehensive Income (Loss), Net of Tax	65	112	200	343
Comprehensive Income Attributable to Common Shareholders	165,793	155,052	363,785	339,031
Public Service Company of New Hampshire
Net Income	47,151	40,879	118,384	100,512
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	268	268	806	806
Changes in Unrealized (Losses)/Gains on Marketable Securities	(8)	10	17	75
Other Comprehensive Income (Loss), Net of Tax	260	278	823	881
Comprehensive Income Attributable to Common Shareholders	$ 47,411	$ 41,157	$ 119,207	$ 101,393

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Adoption of New Accounting Standard	Common Shares	Capital Surplus, Paid In	Retained Earnings	Retained EarningsAdoption of New Accounting Standard	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	The Connecticut Light and Power Company	The Connecticut Light and Power CompanyAdoption of New Accounting Standard	The Connecticut Light and Power CompanyCommon Shares	The Connecticut Light and Power CompanyCapital Surplus, Paid In	The Connecticut Light and Power CompanyRetained Earnings	The Connecticut Light and Power CompanyRetained EarningsAdoption of New Accounting Standard	The Connecticut Light and Power CompanyAccumulated Other Comprehensive Income (Loss)	NSTAR Electric Company	NSTAR Electric CompanyAdoption of New Accounting Standard	NSTAR Electric CompanyCommon Shares	NSTAR Electric CompanyCapital Surplus, Paid In	NSTAR Electric CompanyRetained Earnings	NSTAR Electric CompanyRetained EarningsAdoption of New Accounting Standard	NSTAR Electric CompanyAccumulated Other Comprehensive Income (Loss)	Public Service Company of New Hampshire	Public Service Company of New HampshireAdoption of New Accounting Standard	Public Service Company of New HampshireCommon Shares	Public Service Company of New HampshireCapital Surplus, Paid In	Public Service Company of New HampshireRetained Earnings	Public Service Company of New HampshireRetained EarningsAdoption of New Accounting Standard	Public Service Company of New HampshireAccumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2018			316,885,808								6,035,205							200							301
Balance at Dec. 31, 2018	$ 11,486,817		$ 1,669,392	$ 6,241,222	$ 3,953,974		$ (60,000)	$ (317,771)	$ 4,199,317		$ 60,352	$ 2,410,765	$ 1,727,899		$ 301	$ 3,730,155		$ 0	$ 1,633,442	$ 2,098,091		$ (1,378)	$ 1,302,541		$ 0	$ 678,134	$ 627,258		$ (2,851)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	310,558				310,558				110,471				110,471			94,014				94,014			32,781				32,781
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Shares	(169,757)				(169,757)				(99,000)				(99,000)			(60,600)				(60,600)			(19,000)				(19,000)
Long-Term Incentive Plan Activity	(16,609)			(16,609)
Issuance of Treasury Shares (in shares)			461,662
Issuance of Treasury Shares	26,109			17,476				8,633
Capital Contributions from Eversource Parent																20,000			20,000
Other Comprehensive Income (Loss)	2,196						2,196		17						17	117						117	307						307
Balance (in shares) at Mar. 31, 2019			317,347,470								6,035,205							200							301
Balance at Mar. 31, 2019	11,637,434		$ 1,669,392	6,242,089	4,092,895		(57,804)	(309,138)	4,209,415		$ 60,352	2,410,765	1,737,980		318	3,783,196		$ 0	1,653,442	2,131,015		(1,261)	1,316,629		$ 0	678,134	641,039		(2,544)
Balance (in shares) at Dec. 31, 2018			316,885,808								6,035,205							200							301
Balance at Dec. 31, 2018	11,486,817		$ 1,669,392	6,241,222	3,953,974		(60,000)	(317,771)	4,199,317		$ 60,352	2,410,765	1,727,899		301	3,730,155		$ 0	1,633,442	2,098,091		(1,378)	1,302,541		$ 0	678,134	627,258		(2,851)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	664,655								326,962							338,688							100,512
Dividends on Preferred Stock	(5,600)
Other Comprehensive Income (Loss)	7,983								24							343							881
Balance (in shares) at Sep. 30, 2019			323,733,423								6,035,205							200							301
Balance at Sep. 30, 2019	12,121,614		$ 1,699,292	6,675,889	4,100,220		(52,017)	(301,770)	4,180,334		$ 60,352	2,410,765	1,708,892		325	3,915,916		$ 0	1,663,442	2,253,509		(1,035)	1,151,934		$ 0	678,134	475,770		(1,970)
Balance (in shares) at Mar. 31, 2019			317,347,470								6,035,205							200							301
Balance at Mar. 31, 2019	11,637,434		$ 1,669,392	6,242,089	4,092,895		(57,804)	(309,138)	4,209,415		$ 60,352	2,410,765	1,737,980		318	3,783,196		$ 0	1,653,442	2,131,015		(1,261)	1,316,629		$ 0	678,134	641,039		(2,544)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	33,334				33,334				104,804				104,804			89,734				89,734			26,852				26,852
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Shares	(169,857)				(169,857)				(176,400)				(176,400)			(121,200)				(121,200)			(214,000)				(214,000)
Issuance of Common Shares (in shares)			5,980,000
Issuance of Common Shares	433,550		$ 29,900	403,650
Long-Term Incentive Plan Activity	6,470			6,470
Issuance of Treasury Shares (in shares)			246,969
Issuance of Treasury Shares	18,027			13,448				4,579
Capital Stock Expense	(6,648)			(6,648)
Other									1				1
Other Comprehensive Income (Loss)	4,163						4,163		8						8	114						114	296						296
Balance (in shares) at Jun. 30, 2019			323,574,439								6,035,205							200							301
Balance at Jun. 30, 2019	11,954,593		$ 1,699,292	6,659,009	3,954,492		(53,641)	(304,559)	4,136,438		$ 60,352	2,410,765	1,664,995		326	3,751,354		$ 0	1,653,442	2,099,059		(1,147)	1,129,777		$ 0	678,134	453,891		(2,248)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	320,764				320,764				111,687				111,687			154,940				154,940			40,879				40,879
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Shares	(173,156)				(173,156)				(66,400)				(66,400)										(19,000)				(19,000)
Long-Term Incentive Plan Activity	6,697			6,697
Issuance of Treasury Shares (in shares)			158,984
Issuance of Treasury Shares	12,972			10,183				2,789
Capital Contributions from Eversource Parent																10,000			10,000
Other Comprehensive Income (Loss)	1,624						1,624		(1)						(1)	112						112	278						278
Balance (in shares) at Sep. 30, 2019			323,733,423								6,035,205							200							301
Balance at Sep. 30, 2019	$ 12,121,614		$ 1,699,292	6,675,889	4,100,220		(52,017)	(301,770)	4,180,334		$ 60,352	2,410,765	1,708,892		325	3,915,916		$ 0	1,663,442	2,253,509		(1,035)	1,151,934		$ 0	678,134	475,770		(1,970)
Balance (in shares) at Dec. 31, 2019	329,880,645		329,880,645								6,035,205							200							301
Balance at Dec. 31, 2019	$ 12,629,994	$ (1,514)	$ 1,729,292	7,087,768	4,177,048	$ (1,514)	(65,059)	(299,055)	4,387,825	$ (900)	$ 60,352	2,535,765	1,791,392	$ (900)	316	4,159,884	$ (161)	$ 0	1,813,442	2,346,287	$ (161)	155	1,391,733	$ (300)	$ 0	903,134	490,306	$ (300)	(1,707)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	336,633				336,633				118,738				118,738			100,390				100,390			39,601				39,601
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Shares	(187,462)				(187,462)				(69,500)				(69,500)			(196,500)				(196,500)			(22,300)				(22,300)
Issuance of Common Shares (in shares)			5,960,000
Issuance of Common Shares	432,100		$ 29,800	402,300
Long-Term Incentive Plan Activity	(15,295)			(15,295)
Issuance of Treasury Shares (in shares)			570,542
Issuance of Treasury Shares	27,746			17,230				10,516
Capital Stock Expense	(12,314)			(12,314)
Other Comprehensive Income (Loss)	1,948						1,948		(1)						(1)	67						67	278						278
Balance (in shares) at Mar. 31, 2020			336,411,187								6,035,205							200							301
Balance at Mar. 31, 2020	$ 13,209,956		$ 1,759,092	7,479,689	4,322,825		(63,111)	(288,539)	4,434,772		$ 60,352	2,535,765	1,838,340		315	4,063,190		$ 0	1,813,442	2,249,526		222	1,409,012		$ 0	903,134	507,307		(1,429)
Balance (in shares) at Dec. 31, 2019	329,880,645		329,880,645								6,035,205							200							301
Balance at Dec. 31, 2019	$ 12,629,994	$ (1,514)	$ 1,729,292	7,087,768	4,177,048	$ (1,514)	(65,059)	(299,055)	4,387,825	$ (900)	$ 60,352	2,535,765	1,791,392	$ (900)	316	4,159,884	$ (161)	$ 0	1,813,442	2,346,287	$ (161)	155	1,391,733	$ (300)	$ 0	903,134	490,306	$ (300)	(1,707)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	938,883								356,106							363,585							118,384
Dividends on Preferred Stock	(5,600)
Other Comprehensive Income (Loss)	$ 4,662								(9)							200							823
Balance (in shares) at Sep. 30, 2020	342,797,473		342,797,473								6,035,205							200							301
Balance at Sep. 30, 2020	$ 13,980,017		$ 1,789,092	7,996,976	4,535,860		(60,397)	(281,514)	4,794,352		$ 60,352	2,660,765	2,072,928		307	4,325,539		$ 0	1,813,442	2,511,742		355	1,488,340		$ 0	903,134	586,090		(884)
Balance (in shares) at Mar. 31, 2020			336,411,187								6,035,205							200							301
Balance at Mar. 31, 2020	13,209,956		$ 1,759,092	7,479,689	4,322,825		(63,111)	(288,539)	4,434,772		$ 60,352	2,535,765	1,838,340		315	4,063,190		$ 0	1,813,442	2,249,526		222	1,409,012		$ 0	903,134	507,307		(1,429)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	254,112				254,112				117,271				117,271			97,468				97,468			31,632				31,632
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Shares	(190,964)				(190,964)
Issuance of Common Shares (in shares)			6,000,000
Issuance of Common Shares	517,560		$ 30,000	487,560
Long-Term Incentive Plan Activity	7,694			7,694
Issuance of Treasury Shares (in shares)			216,675
Issuance of Treasury Shares	16,548			12,524				4,024
Capital Stock Expense	(8,321)			(8,321)
Other Comprehensive Income (Loss)	553						553		3						3	68						68	285						285
Balance (in shares) at Jun. 30, 2020			342,627,862								6,035,205							200							301
Balance at Jun. 30, 2020	13,805,258		$ 1,789,092	7,979,146	4,384,093		(62,558)	(284,515)	4,550,656		$ 60,352	2,535,765	1,954,221		318	4,160,236		$ 0	1,813,442	2,346,504		290	1,440,929		$ 0	903,134	538,939		(1,144)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	348,140				348,140				120,097				120,097			165,728				165,728			47,151				47,151
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Shares	(194,493)				(194,493)
Long-Term Incentive Plan Activity	6,921			6,921
Issuance of Treasury Shares (in shares)			169,611
Issuance of Treasury Shares	13,910			10,909				3,001
Capital Contributions from Eversource Parent									125,000			125,000
Other Comprehensive Income (Loss)	$ 2,161						2,161		(11)						(11)	65						65	260						260
Balance (in shares) at Sep. 30, 2020	342,797,473		342,797,473								6,035,205							200							301
Balance at Sep. 30, 2020	$ 13,980,017		$ 1,789,092	$ 7,996,976	$ 4,535,860		$ (60,397)	$ (281,514)	$ 4,794,352		$ 60,352	$ 2,660,765	$ 2,072,928		$ 307	$ 4,325,539		$ 0	$ 1,813,442	$ 2,511,742		$ 355	$ 1,488,340		$ 0	$ 903,134	$ 586,090		$ (884)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Dividends on Common Shares (in dollars per share)	$ 0.5675	$ 0.5675	$ 0.5675	$ 0.535	$ 0.535	$ 0.535
Issuance of Common Shares, par value (in dollars per share)	$ 5	$ 5	$ 5

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating Activities:
Net Income	$ 938,883	$ 664,655
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	721,179	656,632
Deferred Income Taxes	156,795	73,487
Uncollectible Expense	31,101	46,417
Pension, SERP and PBOP Expense, Net	9,153	18,507
Pension and PBOP Contributions	(107,985)	(120,373)
Regulatory (Under)/Over Recoveries, Net	(29,287)	80,688
Amortization	130,687	183,760
Proceeds from DOE Spent Nuclear Fuel Litigation	0	68,840
Impairment of Northern Pass Transmission	0	239,644
Other	(69,216)	(185,625)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(193,895)	(57,011)
Fuel, Materials, Supplies and REC Inventory	21,102	34,030
Taxes Receivable/Accrued, Net	89,759	53,687
Accounts Payable	(121,034)	(157,355)
Other Current Assets and Liabilities, Net	(81,033)	(105,133)
Net Cash Flows Provided by Operating Activities	1,496,209	1,494,850
Investing Activities:
Investments in Property, Plant and Equipment	(2,101,564)	(2,129,037)
Proceeds from Sales of Marketable Securities	386,712	458,322
Purchases of Marketable Securities	(391,368)	(405,095)
Proceeds from the Sale of Hingham Water System	110,536	0
Investments in Unconsolidated Affiliates, Net	(31,677)	(374,913)
Other Investing Activities	17,647	(1,126)
Net Cash Flows Used in Investing Activities	(2,009,714)	(2,451,849)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	929,025	426,902
Cash Dividends on Common Shares	(555,655)	(495,571)
Cash Dividends on Preferred Stock	(5,639)	(5,639)
(Decrease)/Increase in Notes Payable	(1,174,870)	(197,500)
Repayment of Rate Reduction Bonds	(43,210)	(52,332)
Issuance of Long-Term Debt	2,360,000	1,475,000
Retirement of Long-Term Debt	(302,236)	(250,855)
Other Financing Activities	18,030	(450)
Net Cash Flows Provided by/(Used in) Financing Activities	1,225,445	899,555
Net Increase/(Decrease) in Cash and Restricted Cash	711,940	(57,444)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	117,063	209,324
Cash, Cash Equivalents and Restricted Cash - End of Period	829,003	151,880
The Connecticut Light and Power Company
Operating Activities:
Net Income	356,106	326,962
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	238,735	224,095
Deferred Income Taxes	92,590	19,999
Uncollectible Expense	10,013	12,084
Pension, SERP and PBOP Expense, Net	8,629	9,843
Pension Contributions	(23,200)	(24,000)
Regulatory (Under)/Over Recoveries, Net	(32,051)	32,435
Amortization of Regulatory Assets, Net	37,215	78,453
Other	(63,525)	(66,737)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(153,464)	(70,996)
Taxes Receivable/Accrued, Net	(1,515)	32,708
Accounts Payable	(1,976)	8,604
Other Current Assets and Liabilities, Net	(68,316)	(51,937)
Net Cash Flows Provided by Operating Activities	399,241	531,513
Investing Activities:
Investments in Property, Plant and Equipment	(609,690)	(699,288)
Other Investing Activities	496	645
Net Cash Flows Used in Investing Activities	(609,194)	(698,643)
Financing Activities:
Cash Dividends on Common Shares	(69,500)	(341,800)
Cash Dividends on Preferred Stock	(4,169)	(4,169)
Capital Contributions from Eversource Parent	125,000	0
Issuance of Long-Term Debt	0	500,000
Retirement of Long-Term Debt	0	(250,000)
Increase in Notes Payable to Eversource Parent	172,100	173,100
Other Financing Activities	(1,214)	12,667
Net Cash Flows Provided by/(Used in) Financing Activities	222,217	89,798
Net Increase/(Decrease) in Cash and Restricted Cash	12,264	(77,332)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	4,971	91,613
Cash, Cash Equivalents and Restricted Cash - End of Period	17,235	14,281
NSTAR Electric Company
Operating Activities:
Net Income	363,585	338,688
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	238,232	220,303
Deferred Income Taxes	13,436	11,080
Uncollectible Expense	11,321	18,598
Pension, SERP and PBOP Income, Net	(13,714)	(9,779)
Pension and PBOP Contributions	(650)	(4,910)
Regulatory (Under)/Over Recoveries, Net	(20,047)	46,543
Amortization of Regulatory Assets, Net	69,139	73,064
Other	(25,508)	(50,685)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(104,528)	(68,167)
Fuel, Materials, Supplies and REC Inventory	27,709	24,033
Taxes Receivable/Accrued, Net	55,405	66,917
Accounts Payable	(57,300)	(47,256)
Other Current Assets and Liabilities, Net	(54,481)	(31,495)
Net Cash Flows Provided by Operating Activities	502,599	586,934
Investing Activities:
Investments in Property, Plant and Equipment	(655,039)	(636,214)
Other Investing Activities	138	67
Net Cash Flows Used in Investing Activities	(654,901)	(636,147)
Financing Activities:
Cash Dividends on Common Shares	(196,500)	(181,800)
Cash Dividends on Preferred Stock	(1,470)	(1,470)
Capital Contributions from Eversource Parent	0	30,000
Increase in Notes Payable to Eversource Parent	6,300	48,700
(Decrease)/Increase in Notes Payable	50,000	(250,500)
Issuance of Long-Term Debt	400,000	400,000
Retirement of Long-Term Debt	(95,000)	0
Other Financing Activities	(4,931)	(3,868)
Net Cash Flows Provided by/(Used in) Financing Activities	158,399	41,062
Net Increase/(Decrease) in Cash and Restricted Cash	6,097	(8,151)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	6,312	14,659
Cash, Cash Equivalents and Restricted Cash - End of Period	12,409	6,508
Public Service Company of New Hampshire
Operating Activities:
Net Income	118,384	100,512
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	74,494	69,720
Deferred Income Taxes	13,959	12,960
Uncollectible Expense	2,058	4,977
Pension, SERP and PBOP Expense, Net	(894)	683
Pension Contributions	(19,500)	(15,400)
Regulatory (Under)/Over Recoveries, Net	(22,203)	(13,347)
Amortization of Regulatory Assets, Net	39,034	39,944
Other	(7,545)	(23,865)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(24,562)	(13,498)
Fuel, Materials, Supplies and REC Inventory	(301)	13,545
Taxes Receivable/Accrued, Net	1,313	31,909
Accounts Payable	(29,388)	(12,100)
Other Current Assets and Liabilities, Net	4,363	6,754
Net Cash Flows Provided by Operating Activities	149,212	202,794
Investing Activities:
Investments in Property, Plant and Equipment	(248,899)	(209,031)
Other Investing Activities	1,969	904
Net Cash Flows Used in Investing Activities	(246,930)	(208,127)
Financing Activities:
Cash Dividends on Common Shares	(22,300)	(252,000)
Repayment of Rate Reduction Bonds	(43,210)	(52,332)
Issuance of Long-Term Debt	150,000	300,000
Increase in Notes Payable to Eversource Parent	2,100	(14,900)
Other Financing Activities	(2,965)	(4,146)
Net Cash Flows Provided by/(Used in) Financing Activities	83,625	(23,378)
Net Increase/(Decrease) in Cash and Restricted Cash	(14,093)	(28,711)
Cash, Cash Equivalents and Restricted Cash - Beginning of Period	36,688	52,723
Cash, Cash Equivalents and Restricted Cash - End of Period	$ 22,595	$ 24,012

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2020
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, NSTAR Gas and Eversource Gas Company of Massachusetts (natural gas utilities) and Aquarion (water utilities). Eversource provides energy delivery and/or water service to approximately 4.3 million electric, natural gas and water customers through nine regulated utilities in Connecticut, Massachusetts and New Hampshire. On October 9, 2020, Eversource completed the acquisition of certain assets that comprised NiSource’s local natural gas distribution business in Massachusetts, which was previously doing business as Columbia Gas of Massachusetts (CMA). The natural gas distribution assets acquired from CMA were assigned to Eversource Gas Company of Massachusetts, an indirect wholly-owned subsidiary of Eversource formed in 2020. The LNG assets acquired from CMA were assigned to Hopkinton LNG Corp. The cash purchase price was $1.1 billion plus a target working capital amount, which is subject to adjustment to reflect actual working capital as of the closing date. See Note 17, "Acquisition of Assets of Columbia Gas of Massachusetts," for further information. 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 2019 Form 10-K, which was filed with the SEC on February 27, 2020. 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, 2020 and December 31, 2019 , and the results of operations, comprehensive income and common shareholders' equity for the three and nine months ended September 30, 2020 and 2019 , and the cash flows for the nine months ended September 30, 2020 and 2019 . The results of operations and comprehensive income for the three and nine months ended September 30, 2020 and 2019 and the cash flows for the nine months ended September 30, 2020 and 2019 are not necessarily indicative of the results expected for a full year. Eversource consolidates the operations of CYAPC and YAEC, both of which are inactive regional nuclear power companies engaged in the long-term storage of their spent nuclear fuel. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership and voting interests 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 holds several equity ownership interests that are not consolidated and are accounted for under the equity method. Eversource's utility subsidiaries' electric, natural gas and water distribution and transmission businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. COVID-19 has adversely affected workers and the economy and caused volatility in the financial markets. Due to the inherent uncertainty of the unprecedented and evolving situation, we continue to closely monitor how COVID-19 related developments affect Eversource. As of the date of our filing and based on available information, we have not experienced significant impacts directly related to the pandemic that have adversely affected our current operations, financial position, results of operations, and cash flows. The extent of the impact to us in the future will vary and depend in large part on the duration, scope and severity of the pandemic and the timing and extent of COVID-19 relief legislation, and the resulting impact on economic, health care and capital market conditions. The future impact will also depend on the outcome of planned proceedings before our state regulatory commissions to recover our incremental costs associated with COVID-19. We believe that we have in place, or are developing, successful mechanisms with our state regulatory commissions that allow, or will allow, us to recover our incremental costs associated with COVID-19, which include uncollectible customer receivable expenses, while balancing the impact on our customers’ bills and our operating cash flows. See Note 1C, "Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts," for discussion of our evaluation of the allowance for doubtful accounts as of September 30, 2020 in light of the COVID-19 pandemic. An extended economic slowdown has resulted in lower demand for electricity, natural gas and/or water by our commercial and industrial customers. However, fluctuations in retail sales volumes for CL&P, NSTAR Electric, Yankee Gas, NSTAR Gas, Eversource Gas Company of Massachusetts, and our Connecticut water distribution business do not materially impact earnings due to their respective state regulatory commission-approved distribution revenue decoupling mechanisms. As of September 30, 2020 , we did not identify indicators or triggering events for impairments to our goodwill, long-lived assets, available-for-sale debt securities, or equity method investment carrying values. 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 December 2019, the FASB issued Accounting Standards Update (ASU) 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the general principles of current income tax guidance in ASC 740 and simplifies and improves consistency in application of that income tax guidance through clarifications of and amendments to ASC 740. The guidance is effective in the first quarter of 2021. The ASU is not expected to have a material impact on the financial statements of Eversource, CL&P, NSTAR Electric and PSNH. Accounting Standards Recently Adopted: On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), which provides a model for recognizing credit losses on financial instruments based on an estimate of current expected losses, requiring immediate recognition of credit losses expected over the life of a financial instrument. The Company determined the impacts of this standard on the allowance for credit losses on its financial instruments, primarily accounts receivable. As of January 1, 2020, the Company recorded increases to the allowance for uncollectible accounts for late fees and other receivable amounts of $1.6 million , $0.9 million , $0.2 million and $0.3 million at Eversource, CL&P, NSTAR Electric and PSNH, respectively. The impact to retained earnings, net of tax, was $1.5 million , $0.9 million , $0.2 million and $0.3 million at Eversource, CL&P, NSTAR Electric and PSNH, respectively. The Company also adjusted the allowance for uncollectible amounts of hardship receivables and other low-income assistance programs, which are ultimately collectible in rates at specified points in time under approved regulatory mechanisms. The impact on the allowance, which was offset in other long-term assets on the balance sheets, was an increase of $22.2 million and $21.3 million at Eversource and CL&P, respectively, and a decrease of $1.5 million at NSTAR Electric. See Note 1C, “Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts,” for further information. The Company adopted ASU 2017-04, Intangibles - Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment as of January 1, 2020 . The ASU simplified the accounting for goodwill impairment by removing a complex step in the goodwill impairment test. Under the guidance, goodwill impairment is measured as the amount by which its carrying value exceeds its fair value. The ASU is not expected to have an impact on the financial statements of Eversource. On January 1, 2020, the Company adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The ASU aligned the requirements for capitalizing costs incurred to implement a cloud computing arrangement with existing internal-use software guidance. The prospective implementation of this standard did not have any impact on the financial statements of Eversource, CL&P, NSTAR Electric or PSNH for the period ending September 30, 2020 . On January 1, 2020, the Company prospectively adopted ASU 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement . The ASU modified fair value disclosure requirements . The standard includes new disclosure requirements for Level 3 unobservable inputs and eliminated the requirement to disclose certain information relating to transfers between levels. The modified disclosures are included in Note 1D, “Summary of Significant Accounting Policies - Fair Value Measurements,” and Note 4, “Derivative Instruments.” C. Allowance for Uncollectible Accounts Receivables, Net on the balance sheets primarily i ncludes trade receivables from retail customers and customers related to wholesale transmission contracts, wholesale market sales, sales of RECs and property rentals. Receivables, Net also includes customer receivables for the purchase of electricity from a competitive third party supplier, the current portion of customer energy efficiency loans, property damage receivables and other miscellaneous receivables. There is no material concentration of receivables. Receivables are recorded at amortized cost, net of a credit loss provision (or allowance for uncollectible accounts). Receivables are presented net of expected credit losses at estimated net realizable value by maintaining an allowance for uncollectible accounts. Effective January 1, 2020, the current expected credit loss (CECL) model was applied to receivables for purposes of calculating the allowance for uncollectible accounts. This model is based on expected losses and results in the recognition of estimated expected credit losses, including uncollectible amounts for both billed and unbilled revenues, over the life of the receivable at the time a receivable is recorded. The allowance for uncollectible accounts is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. Factors in determining credit loss include historical collection, write-off experience, and management's assessment of collectibility from customers, including current conditions, reasonable forecasts, and expectations of future collectibility and collection efforts. Management continuously assesses the collectibility of receivables and adjusts estimates based on actual experience and future expectations based on economic indicators, collection efforts and other factors. Management also monitors the aging analysis of receivables to determine if there are changes in the collections of accounts receivable. Receivable balances are written off against the allowance for uncollectible accounts when the customer accounts are no longer in service and these balances are deemed to be uncollectible. As of September 30, 2020 , management evaluated the adequacy of the allowance for uncollectible accounts in light of the COVID-19 pandemic and the related economic downturn. This evaluation included an analysis of collection and customer payment trends in 2020, economic conditions, flexible payment plans and financial hardship arrearage management programs being offered to customers, and the impacts of federal governmental pandemic relief programs for our customers and the expansion of unemployment benefit initiatives, which help to mitigate the potential for increasing customer account delinquencies. Additionally, management considered past economic declines and corresponding uncollectible reserves as part of the current assessment. This evaluation has shown that our operating companies have experienced an increase in aged receivables and some lower cash collections from customers because of the moratorium on disconnections and the economic slowdown resulting from the COVID-19 pandemic. Based upon the evaluation performed, for the three and nine months ended September 30, 2020, management increased the allowance for uncollectible costs incurred as a result of COVID-19 by $11.3 million and $16.5 million for Eversource, respectively ( $2.8 million for CL&P for both periods, $5.1 million for NSTAR Electric for both periods, and $1.5 million for PSNH for both periods). These COVID-19 related uncollectible amounts were deferred either as incremental regulatory costs or deferred through existing regulatory tracking mechanisms that recover uncollectible energy supply costs as management believes it is probable that these costs will ultimately be recovered from customers in rates. Management concluded that the reserve balance as of September 30, 2020 adequately reflected the collection risk and net realizable value for Eversource’s receivables. Management will continue to evaluate the adequacy of the uncollectible allowance in future reporting periods based on an ongoing assessment of accounts receivable collections, delinquency statistics, and analysis of aging-based quantitative assessments. 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. Hardship customers are protected from shut-off in certain circumstances, and historical collection experience has reflected a higher default risk as compared to the rest of the receivable population. As a result of the adoption of ASU 2016-13, management aligned the allowance for uncollectible hardship accounts across all regulatory jurisdictions, using a higher credit risk profile for this pool of trade receivables as compared to non-hardship receivables. Implementation impacts of the accounting standard on the allowance for uncollectible hardship accounts are reflected in the rollforward of the uncollectible allowance in the table below. The allowance for uncollectible hardship accounts is included in the total uncollectible allowance balance. The total allowance for uncollectible accounts is included in Receivables, Net on the balance sheets. The activity in the allowance for uncollectible accounts by portfolio segment is as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Hardship Accounts Retail (Non-Hardship), Wholesale, and Other Receivables Total Allowance Hardship Accounts Retail (Non-Hardship), Wholesale and Other Receivables Total Allowance Hardship Accounts Retail (Non-Hardship), Wholesale, and Other Receivables Total Allowance Total Allowance Three Months Ended Beginning Balance $ 175.5 $ 94.5 $ 270.0 $ 116.3 $ 20.4 $ 136.7 $ 34.6 $ 34.1 $ 68.7 $ 11.8 Uncollectible Expense (1) — 10.5 10.5 — 3.8 3.8 — 4.5 4.5 0.8 Uncollectible Costs Deferred (2) 10.1 20.4 30.5 11.2 4.9 16.1 (1.3 ) 10.4 9.1 3.2 Write-Offs (7.3 ) (11.8 ) (19.1 ) (2.6 ) (4.6 ) (7.2 ) (0.2 ) (6.3 ) (6.5 ) (2.0 ) Recoveries Collected 0.4 2.7 3.1 0.3 1.1 1.4 — 1.0 1.0 0.2 Ending Balance $ 178.7 $ 116.3 $ 295.0 $ 125.2 $ 25.6 $ 150.8 $ 33.1 $ 43.7 $ 76.8 $ 14.0 Nine Months Ended Beginning Balance $ 143.3 $ 81.5 $ 224.8 $ 80.1 $ 17.2 $ 97.3 $ 43.9 $ 31.5 $ 75.4 $ 10.5 ASU 2016-13 Implementation Impact on January 1, 2020 21.6 2.2 23.8 21.3 0.9 22.2 (1.6 ) 0.3 (1.3 ) 0.3 Uncollectible Expense (1) — 31.1 31.1 — 10.0 10.0 — 11.3 11.3 2.1 Uncollectible Costs Deferred (2) 24.9 41.5 66.4 32.7 8.3 41.0 (8.4 ) 17.3 8.9 5.6 Write-Offs (12.3 ) (49.3 ) (61.6 ) (10.0 ) (14.0 ) (24.0 ) (0.8 ) (20.5 ) (21.3 ) (5.0 ) Recoveries Collected 1.2 9.3 10.5 1.1 3.2 4.3 — 3.8 3.8 0.5 Ending Balance $ 178.7 $ 116.3 $ 295.0 $ 125.2 $ 25.6 $ 150.8 $ 33.1 $ 43.7 $ 76.8 $ 14.0 (1) Uncollectible expense associated with customer and other accounts receivable is included in Operations and Maintenance expense on the statements of income. For the three and nine months ended September 30, 2019 , uncollectible expense included in Operations and Maintenance Expense was $14.9 million and $46.4 million for Eversource, $4.5 million and $12.1 million for CL&P, $7.0 million and $18.6 million for NSTAR Electric and $1.8 million and $5.0 million for PSNH, respectively. (2) The current period provision for expected credit losses is deferred as a regulatory cost on the balance sheets, as this amount is ultimately recovered in rates. Amounts include uncollectible costs for hardship accounts and other customer receivables, including uncollectible amounts related to COVID-19. D. 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, long-lived assets 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. The 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. Uncategorized - Investments that are measured at net asset value are not categorized within the fair value hierarchy. Determination of Fair Value: The valuation techniques and inputs used in Eversource's fair value measurements are described in Note 4, "Derivative Instruments," Note 5, "Marketable Securities," and Note 10, "Fair Value of Financial Instruments," to the financial statements. E. Other Income, Net The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended September 30, 2020 September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components $ 11.0 $ 0.9 $ 7.2 $ 1.8 $ 10.1 $ 1.7 $ 5.6 $ 1.4 AFUDC Equity 10.3 3.5 5.5 0.9 10.5 3.6 5.6 1.0 Equity in Earnings of Unconsolidated Affiliates (1) 3.9 — 0.1 — 6.1 — 0.2 — Investment Income/(Loss) 1.0 1.3 (0.2 ) 0.2 (2.8 ) (0.8 ) (0.9 ) (0.3 ) Interest Income 1.5 0.2 0.1 1.2 2.9 0.3 0.1 2.5 Gain on Sale of Property 1.5 — — — — — — — Other — — 0.1 — 0.2 — 0.1 — Total Other Income, Net $ 29.2 $ 5.9 $ 12.8 $ 4.1 $ 27.0 $ 4.8 $ 10.7 $ 4.6 For the Nine Months Ended September 30, 2020 September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components $ 34.3 $ 3.0 $ 22.2 $ 5.2 $ 23.2 $ 0.1 $ 18.0 $ 3.5 AFUDC Equity 31.8 11.4 15.8 3.5 34.5 9.4 14.7 2.1 Equity in Earnings of Unconsolidated Affiliates (1) 13.8 — 0.4 — 37.0 0.2 0.6 — Investment (Loss)/Income (1.5 ) — (1.5 ) 0.1 (2.3 ) 0.9 (1.5 ) — Interest Income 3.3 1.8 0.7 2.0 10.8 1.1 0.5 9.0 Gain on Sale of Property 1.8 — 0.3 — 0.2 — — — Other 0.1 0.1 0.3 0.1 0.4 (0.1 ) 0.2 — Total Other Income, Net $ 83.6 $ 16.3 $ 38.2 $ 10.9 $ 103.8 $ 11.6 $ 32.5 $ 14.6 (1) Equity in Earnings of Unconsolidated Affiliates includes $2.4 million of primarily realized gains associated with an investment in a renewable energy fund for the nine months ended September 30, 2020 . For the nine months ended September 30, 2019 , unrealized gains on this investment totaled $20.4 million . F. 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 recorded 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, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Eversource $ 48.4 $ 42.6 $ 129.1 $ 124.0 CL&P 45.6 39.8 114.2 107.8 Separate from above was an amount recorded as Taxes Other Than Income Taxes at CL&P related to the remittance to the State of Connecticut of energy efficiency funds collected from customers of $21.4 million for the nine months ended September 30, 2019. Energy efficiency funds collected from customers after July 1, 2019 are no longer subject to remittance to the State of Connecticut. This amount was recorded separately, with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the Eversource and CL&P statements of income. 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. G. Supplemental Cash Flow Information Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of September 30, 2020 As of September 30, 2019 Eversource $ 357.4 $ 317.8 CL&P 97.8 107.6 NSTAR Electric 92.6 79.0 PSNH 50.0 35.8 The following table reconciles cash and cash equivalents as reported on the balance sheets to the cash, cash equivalents and restricted cash balance as reported on the statements of cash flows: As of September 30, 2020 As of December 31, 2019 (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 $ 730.0 $ 8.2 $ 0.1 $ 0.8 $ 15.4 $ — $ 0.1 $ 0.4 Restricted cash included in: Special Deposits 51.3 8.6 12.2 19.1 52.5 4.6 6.2 32.5 Marketable Securities 45.6 0.4 0.1 0.6 46.0 0.4 — 0.6 Other Long-Term Assets 2.1 — — 2.1 3.2 — — 3.2 Cash, Cash Equivalents and Restricted Cash as reported on the Statements of Cash Flows $ 829.0 $ 17.2 $ 12.4 $ 22.6 $ 117.1 $ 5.0 $ 6.3 $ 36.7 Special Deposits represent cash collections related to the PSNH RRB customer charges that are held in trust, required ISO-NE cash deposits, and CYAPC and YAEC cash balances. Special Deposits are included in Current Assets on the balance sheets. Restricted cash included in Marketable Securities 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 storage obligations.

REGULATORY ACCOUNTING

REGULATORY ACCOUNTING	9 Months Ended
	Sep. 30, 2020
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, plus a return on investment. The application of accounting guidance for rate-regulated enterprises results in recording regulatory assets and liabilities. Regulatory assets represent the deferral of incurred costs that are probable of future recovery in customer rates. Regulatory assets are amortized as the incurred costs are recovered through customer rates. Regulatory liabilities represent either revenues received from customers to fund expected costs that have not yet been incurred or probable future refunds to customers. Management believes it is probable that each of the regulated companies will recover its respective investments in long-lived assets and 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, 2020 As of December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Benefit Costs $ 2,256.1 $ 483.3 $ 601.4 $ 205.7 $ 2,382.9 $ 539.0 $ 629.8 $ 218.2 Income Taxes, Net 731.2 459.8 110.0 13.7 725.8 458.8 108.0 12.8 Securitized Stranded Costs 532.9 — — 532.9 565.3 — — 565.3 Storm Restoration Costs, Net 739.6 510.7 171.4 57.5 540.6 274.6 200.6 65.4 Regulatory Tracker Mechanisms 531.8 174.4 203.0 82.3 411.5 78.3 207.1 65.8 Derivative Liabilities 311.8 311.8 — — 334.5 329.2 — — Goodwill-related 318.9 — 273.8 — 331.5 — 284.6 — Asset Retirement Obligations 105.8 32.3 56.2 3.8 97.2 30.8 50.3 3.6 Other Regulatory Assets 118.0 34.2 56.9 16.5 125.4 25.2 55.2 14.7 Total Regulatory Assets 5,646.1 2,006.5 1,472.7 912.4 5,514.7 1,735.9 1,535.6 945.8 Less: Current Portion 762.9 273.8 278.6 103.6 651.1 178.6 285.6 84.1 Total Long-Term Regulatory Assets $ 4,883.2 $ 1,732.7 $ 1,194.1 $ 808.8 $ 4,863.6 $ 1,557.3 $ 1,250.0 $ 861.7 Storm Event: On August 4, 2020, Tropical Storm Isaias caused catastrophic damage to our electric distribution system, which resulted in significant amounts and durations of customer outages, primarily in Connecticut. In terms of customer outages, this storm was one of the worst in CL&P’s history. PURA has opened an investigation into CL&P's response to Tropical Storm Isaias. PURA will also investigate the prudence of costs incurred by CL&P to restore service as part of its response. CL&P is fully participating in PURA’s investigations and believes that these storm restoration costs were prudently incurred and meet the criteria for cost recovery. A s a result, management does not expect the storm costs to have a material impact on the results of operations of Eversource or CL&P. Based on current estimates, the storm resulted in deferred storm restoration costs of approximately $257 million at CL&P and $276 million at Eversource as of September 30, 2020 . The estimated cost of restoration will change as additional cost information becomes available and final storm costs are deferred or capitalized. The majority of incremental storm costs relate to third-party vendors that are external field crews needed to restore power and address municipal priorities. CL&P’s current estimate of total storm costs includes its projection of the cost of such vendors, but that estimate will change as CL&P receives and examines all storm related invoices. On October 12, 2020, CL&P filed a motion requesting an extension of time to submit a final and complete report on storm costs to PURA by July 1, 2021. On October 23, 2020, PURA denied this request, and on November 2, 2020, CL&P filed a request for reconsideration of PURA’s ruling. CL&P Rate Suspension : On July 31, 2020, PURA temporarily suspended its June 26, 2020 approval of certain delivery rate components effective July 1, 2020, and ordered CL&P to restore rates to those in effect as of June 30, 2020 in order to allow PURA time to reexamine the rates to ensure that CL&P is not over-collecting revenues in the short-term. Rates were adjusted effective August 1, 2020. PURA indicated that this was due to the convergence of a number of recent events, including the COVID-19 crisis and its corresponding effect on customer energy usage, as well as the warmer than normal weather in July. The impact of the temporary suspension of rates is deferred on our balance sheet and results in an increase to our regulatory assets, with no impact on the statement of income, and an expected delay in the collection of our costs. This deferral is reflected within Regulatory Tracker Mechanisms in the table above. Regulatory Costs in Long-Term Assets: Eversource's regulated companies had $183.9 million (including $84.2 million for CL&P, $55.0 million for NSTAR Electric and $15.3 million for PSNH) and $146.0 million (including $51.8 million for CL&P, $55.7 million for NSTAR Electric and $18.0 million for PSNH) of additional regulatory costs as of September 30, 2020 and December 31, 2019 , 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. As of September 30, 2020 , net incremental COVID-19 related costs deferred by Eversource totaled $15.1 million , of which $11.4 million was related to uncollectible expense. Regulatory Liabilities: The components of regulatory liabilities were as follows: As of September 30, 2020 As of December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH EDIT due to Tax Cuts and Jobs Act $ 2,805.3 $ 1,013.9 $ 1,050.1 $ 388.7 $ 2,844.6 $ 1,022.8 $ 1,071.2 $ 392.8 Cost of Removal 610.4 93.0 354.8 12.9 559.8 64.6 330.6 16.3 Benefit Costs 79.5 — 68.7 — 84.5 — 72.2 — Regulatory Tracker Mechanisms 445.7 171.1 181.9 56.2 325.1 94.8 165.6 57.0 AFUDC - Transmission 77.1 45.0 32.1 — 73.2 46.0 27.2 — Other Regulatory Liabilities 158.2 38.2 57.9 9.9 132.0 19.6 59.0 13.1 Total Regulatory Liabilities 4,176.2 1,361.2 1,745.5 467.7 4,019.2 1,247.8 1,725.8 479.2 Less: Current Portion 464.7 164.9 210.7 61.5 361.2 82.8 209.2 65.8 Total Long-Term Regulatory Liabilities $ 3,711.5 $ 1,196.3 $ 1,534.8 $ 406.2 $ 3,658.0 $ 1,165.0 $ 1,516.6 $ 413.4

PROPERTY, PLANT AND EQUIPMENT A

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	9 Months Ended
	Sep. 30, 2020
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, 2020 As of December 31, 2019 (Millions of Dollars) Distribution - Electric $ 16,435.4 $ 15,880.0 Distribution - Natural Gas 4,073.0 3,931.1 Transmission - Electric 11,601.7 10,958.4 Distribution - Water 1,683.8 1,726.5 Solar 201.2 200.2 Utility 33,995.1 32,696.2 Other (1) 1,193.0 1,025.6 Property, Plant and Equipment, Gross 35,188.1 33,721.8 Less: Accumulated Depreciation Utility (7,731.0 ) (7,483.5 ) Other (455.2 ) (387.4 ) Total Accumulated Depreciation (8,186.2 ) (7,870.9 ) Property, Plant and Equipment, Net 27,001.9 25,850.9 Construction Work in Progress 2,091.1 1,734.6 Total Property, Plant and Equipment, Net $ 29,093.0 $ 27,585.5 As of September 30, 2020 As of December 31, 2019 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution - Electric $ 6,728.7 $ 7,414.0 $ 2,332.9 $ 6,485.5 $ 7,163.7 $ 2,271.1 Transmission - Electric 5,299.0 4,608.9 1,689.0 5,043.0 4,411.9 1,498.7 Solar — 201.2 — — 200.2 — Property, Plant and Equipment, Gross 12,027.7 12,224.1 4,021.9 11,528.5 11,775.8 3,769.8 Less: Accumulated Depreciation (2,453.1 ) (3,022.7 ) (832.8 ) (2,385.7 ) (2,895.3 ) (799.9 ) Property, Plant and Equipment, Net 9,574.6 9,201.4 3,189.1 9,142.8 8,880.5 2,969.9 Construction Work in Progress 490.7 742.0 130.4 483.0 592.3 159.6 Total Property, Plant and Equipment, Net $ 10,065.3 $ 9,943.4 $ 3,319.5 $ 9,625.8 $ 9,472.8 $ 3,129.5 (1) These assets are primarily comprised of computer software, hardware and equipment at Eversource Service and buildings at The Rocky River Realty Company. Sale of Water System: On July 31, 2020, Eversource sold its water system and treatment plant that supplies water to the towns of Hingham, Hull and North Cohasset to the town of Hingham, Massachusetts. Net property, plant and equipment of $63.9 million and goodwill of $23.6 million were included in determining the gain on sale. Proceeds from the sale were $110.5 million , with a pre-tax gain of $16.0 million (after-tax gain of $3.5 million ) recognized within Operations and Maintenance Expense on the statement of income in the third quarter of 2020. The assets and liabilities associated with the sale of the business were previously reflected in the Water Distribution segment and reporting unit.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	9 Months Ended
	Sep. 30, 2020
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, 2020 As of December 31, 2019 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Commodity Supply and Price Risk Netting (1) Net Amount Recorded as a Derivative Current Derivative Assets: CL&P Level 3 $ 13.5 $ (0.4 ) $ 13.1 $ 12.2 $ (0.4 ) $ 11.8 Other Level 2 3.4 (0.7 ) 2.7 — — — Long-Term Derivative Assets: CL&P Level 3 59.1 (1.9 ) 57.2 67.5 (2.1 ) 65.4 Current Derivative Liabilities: CL&P Level 3 (69.2 ) — (69.2 ) (67.8 ) — (67.8 ) Other Level 2 — — — (5.2 ) — (5.2 ) Long-Term Derivative Liabilities: CL&P Level 3 (312.9 ) — (312.9 ) (338.6 ) — (338.6 ) Other Level 2 — — — (0.1 ) — (0.1 ) (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 1D, "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 capacities of these contracts as of both September 30, 2020 and December 31, 2019 were 676 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, 2020 and December 31, 2019 , Eversource had New York Mercantile Exchange (NYMEX) financial contracts for natural gas futures in order to reduce variability associated with the price of 11.4 million and 9.6 million MMBtu of natural gas, respectively. For the three months ended September 30, 2020 and 2019 , there were losses of $2.6 million and $9.2 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, 2020 and 2019 , there were losses of $20.6 million and $19.5 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 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 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, 2020 As of December 31, 2019 CL&P Range Weighted Average (1) Period Covered Range Period Covered Capacity Prices $ 4.30 — $5.12 $ 4.57 per kW-Month 2024 - 2026 $ 3.01 — $7.34 per kW-Month 2023 - 2026 Forward Reserve Prices 0.54 — 0.90 0.72 per kW-Month 2021 - 2024 0.80 — 1.90 per kW-Month 2020 - 2024 (1) Unobservable inputs were weighted by the relative future capacity and forward reserve prices and contractual MWs over the periods covered. Exit price premiums of 1 percent through 12 percent , or a weighted average of 10.9 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. The risk premium was weighted by the relative fair value of the net derivative instruments. Significant increases or decreases in future 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) 2020 2019 2020 2019 Derivatives, Net: Fair Value as of Beginning of Period $ (322.0 ) $ (345.4 ) $ (329.2 ) $ (356.5 ) Net Realized/Unrealized Losses Included in Regulatory Assets (4.7 ) (8.5 ) (22.3 ) (16.4 ) Settlements 14.9 11.6 39.7 30.6 Fair Value as of End of Period $ (311.8 ) $ (342.3 ) $ (311.8 ) $ (342.3 )

MARKETABLE SECURITIES

MARKETABLE SECURITIES	9 Months Ended
	Sep. 30, 2020
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: Unrealized gains and losses on equity securities held in Eversource's non-qualified executive benefit trust are recorded in Other Income, Net on the statements of income. The fair value of these equity securities as of September 30, 2020 and December 31, 2019 was $36.8 million and $45.7 million , respectively. For the three months ended September 30, 2020 and 2019 , there were unrealized gains of $1.6 million and $2.4 million , respectively, recorded in Other Income, Net related to these equity securities. For the nine months ended September 30, 2020 and 2019 , there were unrealized losses of $1.0 million and unrealized gains of $5.7 million , respectively. Eversource's equity securities also include CYAPC's and YAEC's marketable securities held in spent nuclear fuel trusts, which had fair values of $189.5 million and $182.8 million as of September 30, 2020 and December 31, 2019 , respectively. Unrealized gains and losses for these spent nuclear fuel 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, 2020 As of December 31, 2019 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 $ 216.1 $ 11.1 $ (0.2 ) $ 227.0 $ 228.4 $ 5.8 $ (0.1 ) $ 234.1 Eversource's debt securities include CYAPC's and YAEC's marketable securities held in spent nuclear fuel trusts in the amounts of $194.0 million and $198.1 million as of September 30, 2020 and December 31, 2019 , 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, excluding amounts related to credit losses or losses on securities intended to be sold, which are recorded in Other Income, Net. There have been no significant unrealized losses and no credit losses for the three and nine months ended September 30, 2020 and 2019 , and no allowance for credit losses as of September 30, 2020 . Factors considered in determining whether a credit loss exists include adverse conditions specifically affecting the issuer, the payment history, ratings and rating changes of the security, and the severity of the impairment. For asset- backed debt securities, underlying collateral and expected future cash flows are also evaluated. Debt securities included in Eversource's non-qualified benefit trust portfolio are investment-grade bonds with a lower default risk based on their credit quality. As of September 30, 2020 , 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) $ 51.1 $ 51.1 One to five years 45.2 47.4 Six to ten years 43.9 47.0 Greater than ten years 75.9 81.5 Total Debt Securities $ 216.1 $ 227.0 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC spent nuclear fuel 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 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 spent nuclear fuel 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, 2020 As of December 31, 2019 Level 1: Mutual Funds and Equities $ 226.3 $ 228.5 Money Market Funds 45.6 46.0 Total Level 1 $ 271.9 $ 274.5 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 64.7 $ 96.8 Corporate Debt Securities 64.9 44.0 Asset-Backed Debt Securities 12.0 12.9 Municipal Bonds 30.4 26.7 Other Fixed Income Securities 9.4 7.7 Total Level 2 $ 181.4 $ 188.1 Total Marketable Securities $ 453.3 $ 462.6 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, 2020
Debt Disclosure [Abstract]
SHORT-TERM AND LONG-TERM DEBT	SHORT-TERM AND LONG-TERM DEBT Short-Term Debt - Commercial Paper Programs and Credit Agreements : As of September 30, 2020 , Eversource parent had a $1.45 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. On November 2, 2020, Eversource parent’s commercial paper program was increased to $2.00 billion . Eversource parent, CL&P, PSNH, NSTAR Gas, Yankee Gas and Aquarion Water Company of Connecticut are parties to a five -year $1.45 billion revolving credit facility, which terminates on December 6, 2024 . On October 21, 2020, Eversource parent and Eversource Gas Company of Massachusetts entered into a short-term $550 million revolving credit facility, which terminates on October 20, 2021. These revolving credit facilities serve to backstop Eversource parent's $2.00 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, which terminates on December 6, 2024 . The revolving credit facility serves to backstop NSTAR Electric's $650 million 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, 2020 December 31, 2019 September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 (Millions of Dollars) Eversource Parent Commercial Paper Program $ — $ 1,224.9 $ 1,450.0 $ 225.1 — % 1.98 % NSTAR Electric Commercial Paper Program 60.5 10.5 589.5 639.5 0.10 % 1.63 % There were no borrowings outstanding on the revolving credit facilities as of September 30, 2020 or December 31, 2019 . On May 15, 2020, CL&P and PSNH entered into uncommitted line of credit agreements, which will expire by May 14, 2021. The CL&P agreements total $450 million and the PSNH agreements total $300 million . There are no borrowings outstanding on either the CL&P or PSNH uncommitted line of credit agreements as of September 30, 2020 . Amounts outstanding under the commercial paper programs are included in Notes Payable and classified in current liabilities on the Eversource and NSTAR Electric balance sheets, as all borrowings are outstanding for no more than 364 days at one time. The Company expects the future operating cash flows of Eversource, CL&P, NSTAR Electric and PSNH, along with existing borrowing availability and access to both debt and equity markets, will be sufficient to meet any working capital and future operating requirements, and capital investment forecasted opportunities. Intercompany Borrowings: Eversource parent uses its available capital resources to provide loans to its subsidiaries to assist in meeting their short-term borrowing needs. Eversource parent records intercompany interest income from its loans to subsidiaries, which is eliminated in consolidation. Intercompany loans from Eversource parent to its subsidiaries are eliminated in consolidation on Eversource's balance sheets. As of September 30, 2020 , there were intercompany loans from Eversource parent to CL&P of $235.9 million , to PSNH of $29.1 million , and to a subsidiary of NSTAR Electric of $36.6 million . As of December 31, 2019 , there were intercompany loans from Eversource parent to CL&P of $ 63.8 million , to PSNH of $ 27.0 million , and to a subsidiary of NSTAR Electric of $ 30.3 million . Intercompany loans from Eversource parent are included in Notes Payable to Eversource Parent and classified in current liabilities on the respective subsidiary's balance sheets. Long-Term Debt Issuance Authorization: On January 27, 2020, the DPU approved NSTAR Gas' request for authorization to issue up to $270 million in long-term debt through December 31, 2021. On July 31, 2020, the NHPUC approved PSNH's request for authorization to issue up to $200 million in long-term debt through December 31, 2020. Long-Term Debt: The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issuance/(Repayment) Issue Date or Repayment Date Maturity Date Use of Proceeds for Issuance/ NSTAR Electric: 3.95% 2020 Debentures $ 400.0 March 2020 April 2030 Refinanced investments in eligible green expenditures, which were previously financed in 2018 and 2019 5.10% Series E Senior Notes (95.0 ) March 2020 March 2020 Paid at maturity PSNH: 2.40% Series U First Mortgage Bonds 150.0 August 2020 September 2050 Refinanced short-term borrowings, funded capital expenditures and working capital Other: Eversource Parent 3.45% Series P Senior Notes 350.0 January 2020 January 2050 Paid short-term borrowings Eversource Parent 3.45% Series P Senior Notes (1) 300.0 August 2020 January 2050 (2) Eversource Parent 0.80% Series Q Senior Notes 300.0 August 2020 August 2025 (2) Eversource Parent 1.65% Series R Senior Notes 600.0 August 2020 August 2030 (2) NSTAR Gas 4.46% Series N First Mortgage Bonds (125.0 ) January 2020 January 2020 Paid at maturity NSTAR Gas 2.33% Series R First Mortgage Bonds 75.0 May 2020 May 2025 Refinanced existing indebtedness, funded capital expenditures and for general corporate purposes NSTAR Gas 3.15% Series S First Mortgage Bonds 115.0 May 2020 May 2050 Refinanced existing indebtedness, funded capital expenditures and for general corporate purposes Yankee Gas 4.87% Series K First Mortgage Bonds (50.0 ) April 2020 April 2020 Paid at maturity Yankee Gas 2.90% Series R First Mortgage Bonds 70.0 September 2020 September 2050 Refinanced existing indebtedness, funded capital expenditures and for general corporate purposes Aquarion Water Company of Massachusetts, Inc. and Aquarion Water Capital of Massachusetts, Inc. various term loans and general mortgage bonds (32.2 ) July 2020 Various Redeemed long-term debt in conjunction with the sale of assets to the Town of Hingham, Massachusetts (1) These senior notes are part of the same series issued by Eversource parent in January 2020. The aggregate outstanding principal amount of these senior notes is now $650 million . (2) The proceeds from these Eversource parent issuances funded a portion of the purchase price for the CMA asset acquisition and refinanced short-term borrowings.

RATE REDUCTION BONDS AND VARIAB

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	9 Months Ended
	Sep. 30, 2020
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: On May 8, 2018, PSNH Funding, a wholly-owned subsidiary of PSNH, 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 are 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 remaining costs resulting from the divestiture of PSNH’s generation assets. PSNH Funding was formed solely to issue RRBs to finance PSNH's unrecovered remaining costs associated with the divestiture of its generation assets. PSNH Funding is considered a 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 sheets and income statements: (Millions of Dollars) Balance Sheet: As of September 30, 2020 As of December 31, 2019 Restricted Cash - Current Portion (included in Current Assets) $ 18.8 $ 32.5 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 2.1 3.2 Securitized Stranded Cost (included in Regulatory Assets) 532.9 565.3 Other Regulatory Liabilities (included in Regulatory Liabilities) 7.2 5.6 Accrued Interest (included in Other Current Liabilities) 3.2 8.6 Rate Reduction Bonds - Current Portion 43.2 43.2 Rate Reduction Bonds - Long-Term Portion 496.9 540.1 (Millions of Dollars) Income Statement: For the Three Months Ended For the Nine Months Ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 10.8 $ 10.8 $ 32.4 $ 32.2 Interest Expense on RRB Principal (included in Interest Expense) 4.9 5.2 14.9 15.9

PENSION BENEFITS AND POSTRETIRE

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION	9 Months Ended
	Sep. 30, 2020
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. 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 (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 meet certain age and service eligibility requirements. The components of net periodic benefit expense/(income) for the Pension, SERP and PBOP Plans, prior to amounts capitalized as Property, Plant and Equipment or deferred as regulatory assets for future recovery, are shown below. The service cost component of net periodic benefit expense/(income), less the capitalized portion, is included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit expense/(income), less the deferred portion, are included in Other Income, Net on the statements of income. 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 PBOP For the Three Months Ended September 30, 2020 For the Three Months Ended September 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 18.7 $ 5.4 $ 3.8 $ 2.0 $ 2.4 $ 0.4 $ 0.5 $ 0.2 Interest Cost 44.4 9.3 9.7 4.8 6.1 1.1 1.7 0.7 Expected Return on Plan Assets (99.2 ) (19.8 ) (25.7 ) (11.1 ) (18.3 ) (2.5 ) (8.5 ) (1.4 ) Actuarial Loss 50.7 9.7 14.0 3.8 2.2 0.3 0.6 0.2 Prior Service Cost/(Credit) 0.2 — — — (5.3 ) 0.3 (4.2 ) 0.1 Total Net Periodic Benefit Expense/(Income) $ 14.8 $ 4.6 $ 1.8 $ (0.5 ) $ (12.9 ) $ (0.4 ) $ (9.9 ) $ (0.2 ) Intercompany Allocations N/A $ 2.4 $ 2.3 $ 0.8 N/A $ (0.3 ) $ (0.4 ) $ (0.1 ) Pension and SERP PBOP For the Nine Months Ended September 30, 2020 For the Nine Months Ended September 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 57.0 $ 16.5 $ 11.4 $ 6.2 $ 7.3 $ 1.3 $ 1.6 $ 0.6 Interest Cost 133.0 28.1 29.0 14.5 18.3 3.3 5.0 2.1 Expected Return on Plan Assets (298.8 ) (59.6 ) (77.2 ) (33.5 ) (55.1 ) (7.4 ) (25.5 ) (4.2 ) Actuarial Loss 150.7 29.4 41.3 11.8 6.3 0.9 1.8 0.6 Prior Service Cost/(Credit) 0.8 — 0.2 — (15.9 ) 0.8 (12.7 ) 0.3 Total Net Periodic Benefit Expense/(Income) $ 42.7 $ 14.4 $ 4.7 $ (1.0 ) $ (39.1 ) $ (1.1 ) $ (29.8 ) $ (0.6 ) Intercompany Allocations N/A $ 6.7 $ 6.5 $ 2.2 N/A $ (0.9 ) $ (1.0 ) $ (0.4 ) Pension and SERP PBOP For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 16.2 $ 4.4 $ 3.6 $ 1.5 $ 2.0 $ 0.3 $ 0.4 $ 0.2 Interest Cost 54.8 11.4 12.3 6.0 8.1 1.6 2.4 0.8 Expected Return on Plan Assets (91.6 ) (18.1 ) (24.2 ) (10.1 ) (16.7 ) (2.2 ) (7.5 ) (1.3 ) Actuarial Loss 35.6 6.3 11.8 2.3 2.1 0.3 0.8 0.1 Prior Service Cost/(Credit) 0.3 — — — (5.8 ) 0.2 (4.2 ) 0.1 Total Net Periodic Benefit Expense/(Income) $ 15.3 $ 4.0 $ 3.5 $ (0.3 ) $ (10.3 ) $ 0.2 $ (8.1 ) $ (0.1 ) Intercompany Allocations N/A $ 2.0 $ 1.9 $ 0.5 N/A $ (0.2 ) $ (0.3 ) $ (0.1 ) Pension and SERP PBOP For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 51.6 $ 13.6 $ 11.0 $ 5.6 $ 5.9 $ 1.1 $ 1.3 $ 0.5 Interest Cost 163.8 34.4 36.6 18.2 24.5 4.7 7.1 2.5 Expected Return on Plan Assets (275.4 ) (55.1 ) (72.9 ) (30.6 ) (50.1 ) (6.9 ) (22.6 ) (4.0 ) Actuarial Loss 107.9 20.6 33.1 8.2 6.2 1.0 2.5 0.3 Prior Service Cost/(Credit) 0.9 — 0.2 — (17.6 ) 0.8 (12.7 ) 0.3 Total Net Periodic Benefit Expense/(Income) $ 48.8 $ 13.5 $ 8.0 $ 1.4 $ (31.1 ) $ 0.7 $ (24.4 ) $ (0.4 ) Intercompany Allocations N/A $ 6.5 $ 6.1 $ 1.8 N/A $ (0.6 ) $ (0.9 ) $ (0.3 )

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2020
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, 2020 As of December 31, 2019 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 55 $ 78.8 57 $ 81.0 CL&P 15 11.6 15 11.4 NSTAR Electric 13 4.6 15 8.0 PSNH 9 7.2 9 7.5 Included in the 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 $69.5 million and $67.9 million as of September 30, 2020 and December 31, 2019 , 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. Long-Term Contractual Arrangements The following is an update to the current status of long-term contractual arrangements set forth in Note 13B of the Eversource 2019 Form 10-K. Renewable Energy : Renewable energy contracts include non-cancelable commitments under contracts of NSTAR Electric for the purchase of energy and RECs from renewable energy facilities. NSTAR Electric October - December 2020 (Millions of Dollars) 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 24.3 $ 98.5 $ 100.0 $ 75.4 $ 72.9 $ 594.5 $ 965.6 C. 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. 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 and affiliates to external parties as of September 30, 2020 : Company Description Maximum Exposure (in millions) Expiration Dates Various Surety Bonds (1) $ 30.9 2020 - 2023 Rocky River Realty Company and Eversource Service Lease Payments for Real Estate 5.6 2024 Bay State Wind LLC Real Estate Purchase 2.5 2021 Sunrise Wind LLC OREC Capacity Production (2) 2.2 - (1) 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. (2) On October 25, 2019, Eversource parent issued a guaranty on behalf of its 50 percent -owned affiliate, Sunrise Wind LLC, whereby Eversource parent will guaranty Sunrise Wind LLC’s performance of certain obligations, in an amount not to exceed $15.4 million , under the Offshore Wind Renewable Energy Certificate Purchase and Sale Agreement (the Agreement). The Agreement was executed on October 23, 2019, by and between the New York State Energy Research and Development Authority (NYSERDA) and Sunrise Wind LLC. The Company regularly reviews performance risk under this arrangement, and in the event it becomes probable that Eversource parent will be required to perform under the guarantee, the amount of probable payment will be recorded. As of September 30, 2020 , the fair value of the guarantee was immaterial. On September 16, 2020, Eversource parent entered into a guaranty on behalf of Eversource Investment LLC, which holds Eversource's investments in wind-related equity method investments, under which Eversource parent would guarantee Eversource Investment LLC's obligations under a letter of credit facility with a financial institution that Eversource Investment LLC may request in an aggregate amount of up to approximately $25 million . D. 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 power facilities and are now engaged in the long-term storage of their spent fuel. The Yankee Companies fund these costs through litigation proceeds received from the DOE and, to the extent necessary, through wholesale, FERC-approved rates charged under power purchase agreements with several New England utilities, including CL&P, NSTAR Electric and PSNH. CL&P, NSTAR Electric and PSNH, in turn recover these costs from their customers through state regulatory commission-approved retail rates. The Yankee Companies collect 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 accept delivery of, and 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 previously awarded the Yankee Companies damages for Phases 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 a fourth set of lawsuits against the DOE in the Court of Federal Claims. The Yankee Companies sought monetary damages totaling $104.4 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). On February 21, 2019, the Yankee Companies received a partial summary judgment and partial final judgment in their favor for the undisputed amount of monetary damages of $103.2 million . The court awarded CYAPC, YAEC and MYAPC damages of $40.7 million , $28.1 million and $34.4 million , respectively. The DOE did not appeal the court's judgment and the decision became final on April 23, 2019. On June 12, 2019, each of the Yankee Companies received the damages proceeds. On June 12, 2019, the court accepted an offer of judgment in the amount of $0.5 million to settle the disputed amount of approximately $1 million in Phase IV contested damages. The Yankee Companies received the $0.5 million payment in July 2019. In September 2019, the Yankee Companies made a required informational filing with FERC as to the use of proceeds, for which approval was received in the fourth quarter of 2019. In December 2019, YAEC and MYAPC returned proceeds of $5.4 million and $21.0 million , respectively, to its member companies, of which the Eversource utilities (CL&P, NSTAR Electric and PSNH) received a total of $2.8 million from YAEC and $5.0 million from MYAPC. The Eversource utilities refund these amounts received to their utility customers. Also, in December 2019, CYAPC paid $29.0 million to the DOE to partially settle its pre-1983 spent nuclear fuel obligation. E. FERC ROE Complaints Four separate complaints were 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, filed on October 1, 2011, December 27, 2012, and July 31, 2014, respectively, 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 billed 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. The ROE originally billed during the period October 1, 2011 (beginning of the first complaint period) 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 the 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 by the U.S. Court of Appeals for the D.C. Circuit (the Court). 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. Eversource has recorded a reserve of $39.1 million (pre-tax and excluding interest) for the second complaint period as of September 30, 2020 and December 31, 2019 . This 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, 2020 and December 31, 2019 . 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. Initial briefs were filed by the NETOs, Complainants and FERC Trial Staff on January 11, 2019 and reply briefs were filed on March 8, 2019. The NETOs' brief was supportive of the overall ROE methodology determined in the October 16, 2018 order provided the FERC does not change the proposed methodology or alter its implementation in a manner that has a material impact on the results. The FERC order included illustrative calculations for the first complaint using FERC's proposed frameworks with financial data from that complaint. Those illustrative calculations indicated that for the first complaint period, for the NETOs, which FERC concludes are of average financial risk, the preliminary just and reasonable base ROE is 10.41 percent and the preliminary incentive cap on total ROE is 13.08 percent . If the results of the illustrative calculations were included in a final FERC order for each of the complaint periods, then a 10.41 percent base ROE and a 13.08 percent incentive cap would not have a significant impact on our financial statements for all of the complaint periods. These preliminary calculations are not binding and do not represent what we believe to be the most likely outcome of a final FERC order. On November 21, 2019, FERC issued Opinion No. 569 affecting the two pending transmission ROE complaints against the Midcontinent ISO (MISO) transmission owners, in which FERC adopted a new methodology for determining base ROEs. Various parties sought rehearing. On December 23, 2019, the NETOs filed supplementary materials in the NETOs' four pending cases to respond to this new methodology because of the uncertainty of the applicability to the NETOs’ cases. On May 21, 2020, the FERC issued its order in Opinion No. 569-A on the rehearing of the MISO transmission owners' cases, in which FERC again changed its methodology for determining the MISO transmission owners' base ROEs. Various parties have appealed the MISO transmission owners' opinion. This new methodology differs significantly from the methodology proposed by FERC in its October 16, 2018 order to determine the NETOs' base ROEs in its four pending cases. Given the significant uncertainty regarding the applicability of the FERC opinions in the MISO transmission owners' two complaint cases to the NETOs' pending four complaint cases, Eversource concluded that there is no reasonable basis for a change to the reserve or recognized ROEs for any of the complaint periods at this time. As well, Eversource cannot reasonably estimate a range of any gain or loss for any of the four complaint proceedings at this time. 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. A change of 10 basis points to the base ROE used to establish the reserves would impact Eversource's after-tax earnings by an average of approximately $3 million for each of the four 15 -month complaint periods. F. Eversource and NSTAR Electric Boston Harbor Civil Action In 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 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 parties reached a settlement pursuant to which HEEC agreed to install a new 115 kV distribution cable across Boston Harbor to Deer Island,

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2020
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, 2020: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 166.6 $ 116.2 $ 122.0 $ 43.0 $ 44.6 $ — $ — Long-Term Debt 15,814.5 17,943.7 3,518.1 4,336.7 3,642.8 4,285.4 1,099.0 1,192.1 Rate Reduction Bonds 540.1 603.0 — — — — 540.1 603.0 As of December 31, 2019: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 162.0 $ 116.2 $ 117.8 $ 43.0 $ 44.2 $ — $ — Long-Term Debt 14,098.2 15,170.2 3,518.1 4,058.0 3,342.1 3,659.9 951.6 1,005.7 Rate Reduction Bonds 583.3 625.9 — — — — 583.3 625.9 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 1D, "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, 2020
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, are as follows: For the Nine Months Ended September 30, 2020 For the Nine Months Ended September 30, 2019 Eversource (Millions of Dollars) Qualified Cash Flow Hedging Instruments Unrealized Gains on Marketable Securities Defined Benefit Plans Total Qualified Cash Flow Hedging Instruments Unrealized Gains/(Losses) on Marketable Securities Defined Benefit Plans Total Balance as of January 1st $ (3.0 ) $ 0.7 $ (62.8 ) $ (65.1 ) $ (4.4 ) $ (0.5 ) $ (55.1 ) $ (60.0 ) OCI Before Reclassifications — 0.3 (1.6 ) (1.3 ) — 1.3 2.6 3.9 Amounts Reclassified from AOCI 1.2 — 4.8 6.0 0.9 — 3.2 4.1 Net OCI 1.2 0.3 3.2 4.7 0.9 1.3 5.8 8.0 Balance as of September 30th $ (1.8 ) $ 1.0 $ (59.6 ) $ (60.4 ) $ (3.5 ) $ 0.8 $ (49.3 ) $ (52.0 ) 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.

COMMON SHARES

COMMON SHARES	9 Months Ended
	Sep. 30, 2020
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, 2020 and December 31, 2019 Issued as of Par Value September 30, 2020 December 31, 2019 Eversource $ 5 380,000,000 357,818,402 345,858,402 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 Common Share Issuances and 2019 Forward Sale Agreement: On June 15, 2020, Eversource completed an equity offering of 6,000,000 common shares at a price per share of $86.26 . Eversource used the net proceeds of this offering to fund a portion of the purchase of the assets of CMA that closed on October 9, 2020. The issuance of these common shares resulted in proceeds of $509.2 million , net of issuance costs. In June 2019, Eversource completed an equity offering consisting of 5,980,000 common shares issued directly by the Company and 11,960,000 common shares issuable pursuant to a forward sale agreement with an investment bank. Under the forward sale agreement, 11,960,000 common shares were borrowed from third parties and sold by the underwriters. The forward sale agreement allowed Eversource, at its election and prior to May 29, 2020, to physically settle the forward sale agreement by issuing common shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreement (initially, $71.48 per share) or, alternatively, to settle the forward sale agreement in whole or in part through the delivery or receipt of shares or cash. The forward sale price was subject to adjustment daily based on a floating interest rate factor and would decrease in respect of certain fixed amounts specified in the agreement, such as dividends. Eversource issued 6,000,000 common shares under the forward sale agreement in December 2019. On March 23, 2020, Eversource physically settled a portion of the forward sale agreement by delivering 1,500,000 common shares in exchange for net proceeds of $105.7 million . Subsequently, on March 26, 2020, Eversource physically settled the remaining portion of the forward sale agreement by delivering 4,460,000 common shares in exchange for net proceeds of $314.1 million . The forward sale price used to determine the cash proceeds received by Eversource was calculated based on the initial forward sale price, as adjusted in accordance with the forward sale agreement. The March and June 2020 common share issuances of 5,960,000 and 6,000,000 , respectively, resulted in total proceeds of $929.0 million , net of issuance costs, and were reflected in shareholders' equity and as financing activities on the statement of cash flows. Issuances of shares under the forward sale agreement are classified as equity transactions. Accordingly, no amounts relating to the forward sale agreement were recorded in the financial statements until settlements took place. Prior to any settlements, the only impact to the financial statements was the inclusion of incremental shares within the calculation of diluted EPS using the treasury stock method. See Note 14, "Earnings Per Share," to the financial statements for information on the forward sale agreement’s impact on the calculation of diluted EPS. Eversource used the net proceeds received from the direct issuance of common shares and the net proceeds received from settlement of the forward sale agreement to repay short-term debt under the commercial paper program, to partially fund the purchase of the assets of CMA, to fund capital spending and clean energy initiatives, and for general corporate purposes. Treasury Shares: As of September 30, 2020 and December 31, 2019 , there were 15,020,929 and 15,977,757 Eversource common shares held as treasury shares, respectively. As of September 30, 2020 and December 31, 2019 , Eversource common shares outstanding were 342,797,473 and 329,880,645 , respectively. Dividends on the preferred stock of CL&P and NSTAR Electric totaled $1.9 million for each of the three months ended September 30, 2020 and 2019 and $5.6 million for each of the nine months ended September 30, 2020 and 2019 . 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, 2020 and December 31, 2019 . 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 SHAREHOLDERS' EQUITY AND

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	9 Months Ended
	Sep. 30, 2020
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, 2020 and December 31, 2019 Issued as of Par Value September 30, 2020 December 31, 2019 Eversource $ 5 380,000,000 357,818,402 345,858,402 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 Common Share Issuances and 2019 Forward Sale Agreement: On June 15, 2020, Eversource completed an equity offering of 6,000,000 common shares at a price per share of $86.26 . Eversource used the net proceeds of this offering to fund a portion of the purchase of the assets of CMA that closed on October 9, 2020. The issuance of these common shares resulted in proceeds of $509.2 million , net of issuance costs. In June 2019, Eversource completed an equity offering consisting of 5,980,000 common shares issued directly by the Company and 11,960,000 common shares issuable pursuant to a forward sale agreement with an investment bank. Under the forward sale agreement, 11,960,000 common shares were borrowed from third parties and sold by the underwriters. The forward sale agreement allowed Eversource, at its election and prior to May 29, 2020, to physically settle the forward sale agreement by issuing common shares in exchange for net proceeds at the then-applicable forward sale price specified by the agreement (initially, $71.48 per share) or, alternatively, to settle the forward sale agreement in whole or in part through the delivery or receipt of shares or cash. The forward sale price was subject to adjustment daily based on a floating interest rate factor and would decrease in respect of certain fixed amounts specified in the agreement, such as dividends. Eversource issued 6,000,000 common shares under the forward sale agreement in December 2019. On March 23, 2020, Eversource physically settled a portion of the forward sale agreement by delivering 1,500,000 common shares in exchange for net proceeds of $105.7 million . Subsequently, on March 26, 2020, Eversource physically settled the remaining portion of the forward sale agreement by delivering 4,460,000 common shares in exchange for net proceeds of $314.1 million . The forward sale price used to determine the cash proceeds received by Eversource was calculated based on the initial forward sale price, as adjusted in accordance with the forward sale agreement. The March and June 2020 common share issuances of 5,960,000 and 6,000,000 , respectively, resulted in total proceeds of $929.0 million , net of issuance costs, and were reflected in shareholders' equity and as financing activities on the statement of cash flows. Issuances of shares under the forward sale agreement are classified as equity transactions. Accordingly, no amounts relating to the forward sale agreement were recorded in the financial statements until settlements took place. Prior to any settlements, the only impact to the financial statements was the inclusion of incremental shares within the calculation of diluted EPS using the treasury stock method. See Note 14, "Earnings Per Share," to the financial statements for information on the forward sale agreement’s impact on the calculation of diluted EPS. Eversource used the net proceeds received from the direct issuance of common shares and the net proceeds received from settlement of the forward sale agreement to repay short-term debt under the commercial paper program, to partially fund the purchase of the assets of CMA, to fund capital spending and clean energy initiatives, and for general corporate purposes. Treasury Shares: As of September 30, 2020 and December 31, 2019 , there were 15,020,929 and 15,977,757 Eversource common shares held as treasury shares, respectively. As of September 30, 2020 and December 31, 2019 , Eversource common shares outstanding were 342,797,473 and 329,880,645 , respectively. Dividends on the preferred stock of CL&P and NSTAR Electric totaled $1.9 million for each of the three months ended September 30, 2020 and 2019 and $5.6 million for each of the nine months ended September 30, 2020 and 2019 . 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, 2020 and December 31, 2019 . 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, 2020
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 and the equity forward sale agreement, as if they were converted into outstanding common shares. The dilutive effect of unvested RSU and performance share awards, as well as the equity forward sale agreement, 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. As described in Note 12, "Common Shares," earnings per share dilution, if any, related to the forward sale agreement is determined under the treasury stock method until settlement of the forward sale agreement. Under this method, the number of Eversource common shares used in calculating diluted EPS is deemed to be increased by the excess, if any, of the number of shares that would be issued upon physical settlement of the forward sale agreement less the number of shares that would be purchased by Eversource in the market (based on the average market pri ce during the same reporting period) using the proceeds receivable upon settlement (based on the adjusted forward sale price at the end of that reporting period). Share dilution occurs when the average market price of Eversource's common shares is higher than the adjusted forward sale price. For the nine months ended September 30, 2020 , there were 52,747 antidilutive share awards excluded from the EPS computation, as their impact would have been antidilutive . Antidilutive shares pertained to a purchase option extended to underwriters in connection with Eversource's common share issuance on June 15, 2020. See Note 12, "Common Shares," for further information. There were no antidilutive share awards excluded from the computation for the three months ended September 30, 2020 and 2019 or the nine months ended September 30, 2019. 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, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Net Income Attributable to Common Shareholders $ 346.3 $ 318.9 $ 933.2 $ 659.0 Weighted Average Common Shares Outstanding: Basic 343,076,614 324,037,169 337,375,172 320,442,253 Dilutive Effect of: Share-Based Compensation Awards and Other 696,988 737,972 686,403 691,636 Equity Forward Sale Agreement — 1,233,201 362,525 437,037 Total Dilutive Effect 696,988 1,971,173 1,048,928 1,128,673 Diluted 343,773,602 326,008,342 338,424,100 321,570,926 Basic EPS $ 1.01 $ 0.98 $ 2.77 $ 2.06 Diluted EPS $ 1.01 $ 0.98 $ 2.76 $ 2.05

REVENUES

REVENUES	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES The following tables present operating revenues disaggregated by revenue source: For the Three Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,183.9 $ 45.5 $ — $ 45.8 $ — $ — $ 1,275.2 Commercial 682.7 41.1 — 17.1 — (1.4 ) 739.5 Industrial 91.0 17.5 — 1.3 — (3.6 ) 106.2 Total Retail Tariff Sales Revenues 1,957.6 104.1 — 64.2 — (5.0 ) 2,120.9 Wholesale Transmission Revenues — — 458.2 — 19.0 (365.6 ) 111.6 Wholesale Market Sales Revenues 79.6 8.7 — 1.1 — — 89.4 Other Revenues from Contracts with Customers 18.4 0.8 3.2 1.8 303.3 (299.0 ) 28.5 Amortization of/(Reserve for) Revenues Subject to Refund 2.3 0.5 — (1.1 ) — — 1.7 Total Revenues from Contracts with Customers 2,057.9 114.1 461.4 66.0 322.3 (669.6 ) 2,352.1 Alternative Revenue Programs 1.7 (4.0 ) (72.3 ) (2.0 ) — 67.0 (9.6 ) Other Revenues (1) 0.7 0.1 0.2 0.1 — — 1.1 Total Operating Revenues $ 2,060.3 $ 110.2 $ 389.3 $ 64.1 $ 322.3 $ (602.6 ) $ 2,343.6 For the Nine Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 3,063.7 $ 399.6 $ — $ 113.2 $ — $ — $ 3,576.5 Commercial 1,815.7 243.5 — 47.7 — (3.7 ) 2,103.2 Industrial 248.4 67.0 — 3.6 — (10.1 ) 308.9 Total Retail Tariff Sales Revenues 5,127.8 710.1 — 164.5 — (13.8 ) 5,988.6 Wholesale Transmission Revenues — — 1,177.9 — 55.6 (981.4 ) 252.1 Wholesale Market Sales Revenues 231.1 31.9 — 2.9 — — 265.9 Other Revenues from Contracts with Customers 56.4 2.5 9.9 5.6 845.1 (838.0 ) 81.5 Amortization of/(Reserve for) Revenues Subject to Refund 6.9 1.6 — (2.8 ) — — 5.7 Total Revenues from Contracts with Customers 5,422.2 746.1 1,187.8 170.2 900.7 (1,833.2 ) 6,593.8 Alternative Revenue Programs 54.8 22.9 (52.7 ) (4.1 ) — 48.9 69.8 Other Revenues (1) 4.9 1.0 0.5 0.5 — — 6.9 Total Operating Revenues $ 5,481.9 $ 770.0 $ 1,135.6 $ 166.6 $ 900.7 $ (1,784.3 ) $ 6,670.5 For the Three Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,041.4 $ 43.0 $ — $ 40.0 $ — $ — $ 1,124.4 Commercial 736.6 41.6 — 17.8 — (1.4 ) 794.6 Industrial 90.6 18.1 — 1.3 — (3.2 ) 106.8 Total Retail Tariff Sales Revenues 1,868.6 102.7 — 59.1 — (4.6 ) 2,025.8 Wholesale Transmission Revenues — — 365.5 — 15.4 (300.7 ) 80.2 Wholesale Market Sales Revenues 33.1 5.5 — 1.3 — — 39.9 Other Revenues from Contracts with Customers 12.3 0.5 3.1 1.7 242.7 (243.0 ) 17.3 Amortization of/(Reserve for) Revenues 4.5 1.5 — (0.8 ) — — 5.2 Total Revenues from Contracts with Customers 1,918.5 110.2 368.6 61.3 258.1 (548.3 ) 2,168.4 Alternative Revenue Programs 6.7 (7.6 ) (20.9 ) 2.6 — 19.0 (0.2 ) Other Revenues (1) 6.4 0.8 0.1 0.3 — — 7.6 Total Operating Revenues $ 1,931.6 $ 103.4 $ 347.8 $ 64.2 $ 258.1 $ (529.3 ) $ 2,175.8 For the Nine Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 2,879.8 $ 402.0 $ — $ 100.5 $ — $ — $ 3,382.3 Commercial 2,002.0 254.9 — 48.1 — (3.4 ) 2,301.6 Industrial 254.0 72.5 — 3.5 — (8.7 ) 321.3 Total Retail Tariff Sales Revenues 5,135.8 729.4 — 152.1 — (12.1 ) 6,005.2 Wholesale Transmission Revenues — — 971.6 — 43.7 (811.4 ) 203.9 Wholesale Market Sales Revenues 123.9 41.6 — 3.2 — — 168.7 Other Revenues from Contracts with Customers 40.0 1.9 9.9 5.2 723.4 (725.2 ) 55.2 (Reserve for)/Amortization of Revenues (1.7 ) 4.7 — (1.9 ) — — 1.1 Total Revenues from Contracts with Customers 5,298.0 777.6 981.5 158.6 767.1 (1,548.7 ) 6,434.1 Alternative Revenue Programs 15.0 — 56.1 4.2 — (50.8 ) 24.5 Other Revenues (1) 14.2 2.3 0.3 0.7 — — 17.5 Total Operating Revenues $ 5,327.2 $ 779.9 $ 1,037.9 $ 163.5 $ 767.1 $ (1,599.5 ) $ 6,476.1 For the Three Months Ended September 30, 2020 For the Three Months Ended September 30, 2019 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 608.7 $ 415.4 $ 159.8 $ 513.6 $ 374.4 $ 153.4 Commercial 244.7 358.3 80.1 247.0 406.1 84.1 Industrial 38.0 30.6 22.4 37.4 32.4 20.8 Total Retail Tariff Sales Revenues 891.4 804.3 262.3 798.0 812.9 258.3 Wholesale Transmission Revenues 233.3 153.1 71.8 175.2 132.9 57.4 Wholesale Market Sales Revenues 60.0 12.1 7.5 13.8 14.4 4.9 Other Revenues from Contracts with Customers 8.1 10.5 3.7 9.0 3.1 4.0 Amortization of Revenues Subject to Refund — — 2.3 — — 4.5 Total Revenues from Contracts with Customers 1,192.8 980.0 347.6 996.0 963.3 329.1 Alternative Revenue Programs (65.0 ) 8.2 (13.8 ) (15.2 ) 9.8 (8.8 ) Other Revenues (1) 0.2 0.7 — 4.1 1.8 0.6 Eliminations (133.7 ) (113.5 ) (50.1 ) (131.0 ) (96.2 ) (40.5 ) Total Operating Revenues $ 994.3 $ 875.4 $ 283.7 $ 853.9 $ 878.7 $ 280.4 For the Nine Months Ended September 30, 2020 For the Nine Months Ended September 30, 2019 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,567.9 $ 1,057.9 $ 437.9 $ 1,426.9 $ 1,027.8 $ 425.1 Commercial 670.4 921.3 225.3 708.4 1,058.3 236.8 Industrial 105.3 82.1 61.0 105.8 90.1 58.1 Total Retail Tariff Sales Revenues 2,343.6 2,061.3 724.2 2,241.1 2,176.2 720.0 Wholesale Transmission Revenues 576.5 430.3 171.1 445.9 383.1 142.6 Wholesale Market Sales Revenues 163.9 39.8 27.4 39.6 55.9 28.4 Other Revenues from Contracts with Customers 25.1 32.4 10.9 27.0 13.2 11.8 Amortization of/(Reserve for) Revenues — — 6.9 — — (1.7 ) Total Revenues from Contracts with Customers 3,109.1 2,563.8 940.5 2,753.6 2,628.4 901.1 Alternative Revenue Programs (27.8 ) 31.1 (1.2 ) 45.6 19.1 6.4 Other Revenues (1) 2.0 2.8 0.6 7.9 5.2 1.4 Eliminations (371.9 ) (327.5 ) (124.6 ) (363.1 ) (294.5 ) (111.1 ) Total Operating Revenues $ 2,711.4 $ 2,270.2 $ 815.3 $ 2,444.0 $ 2,358.2 $ 797.8 (1) Other Revenues include certain fees charged to customers that are not considered revenue from contracts with customers. Other revenues also include lease revenues under lessor accounting guidance of $1.1 million (including $0.2 million at CL&P and $0.7 million at NSTAR Electric) and $1.2 million (including $0.3 million at CL&P and $0.7 million at NSTAR Electric) for the three months ended September 30, 2020 and 2019 , respectively, and $3.2 million (including $0.6 million at CL&P and $2.1 million at NSTAR Electric) and $3.4 million (including $0.7 million at CL&P and $2.0 million at NSTAR Electric) for the nine months ended September 30, 2020 and 2019 , respectively. CL&P, NSTAR Electric, Yankee Gas, NSTAR Gas and the Connecticut water distribution business each have a revenue decoupling mechanism approved by a regulatory commission. The revenue decoupling mechanisms mitigate the impact of lower demand and resulting lost sales revenues by replacing actual customer usage with a fixed annual revenue stream, each of which is reconciled each year as part of our annual decoupling filing in each respective jurisdiction. These revenue decoupling mechanisms qualify as alternative revenue programs in accordance with accounting guidance for rate-regulated operations. The increase in Eversource's electric and natural gas distribution segment revenues from Alternative Revenue Programs for the nine months ended September 30, 2020 , as compared to the nine months ended September 30, 2019

SEGMENT INFORMATION

SEGMENT INFORMATION	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Eversource is organized into 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 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. 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, 4) Eversource Water Ventures, Inc., parent company of Aquarion, 5) the results of other unregulated subsidiaries, which are not part of its core business, and 6) Eversource parent's equity ownership interests that are not consolidated, which primarily include the offshore wind business, a natural gas pipeline owned by Enbridge, Inc., and a renewable energy investment fund. In the ordinary course of business, Yankee Gas and NSTAR Gas purchase natural gas transmission services from the Enbridge, Inc. natural gas pipeline project described above. These affiliate transaction costs total $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, 2020 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 2,060.3 $ 110.2 $ 389.3 $ 64.1 $ 322.3 $ (602.6 ) $ 2,343.6 Depreciation and Amortization (182.0 ) (14.8 ) (70.6 ) (10.8 ) (24.1 ) 0.3 (302.0 ) Other Operating Expenses (1,577.0 ) (104.2 ) (120.6 ) (10.2 ) (271.5 ) 603.1 (1,480.4 ) Operating Income/(Loss) $ 301.3 $ (8.8 ) $ 198.1 $ 43.1 $ 26.7 $ 0.8 $ 561.2 Interest Expense $ (53.3 ) $ (10.1 ) $ (31.1 ) $ (8.0 ) $ (38.7 ) $ 7.1 $ (134.1 ) Other Income, Net 16.0 0.7 6.9 1.6 387.0 (383.0 ) 29.2 Net Income/(Loss) Attributable to Common Shareholders 205.5 (14.0 ) 125.6 23.1 381.2 (375.1 ) 346.3 For the Nine Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 5,481.9 $ 770.0 $ 1,135.6 $ 166.6 $ 900.7 $ (1,784.3 ) $ 6,670.5 Depreciation and Amortization (490.0 ) (55.1 ) (206.8 ) (33.1 ) (68.1 ) 1.2 (851.9 ) Other Operating Expenses (4,309.9 ) (592.0 ) (338.5 ) (60.7 ) (771.4 ) 1,787.9 (4,284.6 ) Operating Income $ 682.0 $ 122.9 $ 590.3 $ 72.8 $ 61.2 $ 4.8 $ 1,534.0 Interest Expense $ (160.7 ) $ (32.1 ) $ (93.8 ) $ (25.1 ) $ (119.0 ) $ 27.6 $ (403.1 ) Other Income, Net 44.9 2.5 22.7 1.7 1,161.7 (1,149.9 ) 83.6 Net Income Attributable to Common Shareholders 450.6 73.8 381.8 35.6 1,108.9 (1,117.5 ) 933.2 Cash Flows Used for Investments in Plant 781.2 322.8 732.4 84.0 181.2 — 2,101.6 For the Three Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,931.6 $ 103.4 $ 347.8 $ 64.2 $ 258.1 $ (529.3 ) $ 2,175.8 Depreciation and Amortization (188.4 ) (16.1 ) (64.3 ) (11.1 ) (17.2 ) 0.6 (296.5 ) Other Operating Expenses (1,448.2 ) (99.3 ) (159.6 ) (25.5 ) (275.9 ) 638.4 (1,370.1 ) Operating Income/(Loss) $ 295.0 $ (12.0 ) $ 123.9 $ 27.6 $ (35.0 ) $ 109.7 $ 509.2 Interest Expense $ (53.2 ) $ (11.7 ) $ (33.6 ) $ (8.9 ) $ (41.7 ) $ 13.9 $ (135.2 ) Other Income/(Loss), Net 13.9 — 61.4 (0.2 ) 497.0 (545.1 ) 27.0 Net Income/(Loss) Attributable to Common Shareholders 197.3 (17.1 ) 107.5 17.5 435.2 (421.5 ) 318.9 For the Nine Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 5,327.2 $ 779.9 $ 1,037.9 $ 163.5 $ 767.1 $ (1,599.5 ) $ 6,476.1 Depreciation and Amortization (517.6 ) (56.0 ) (188.0 ) (35.0 ) (45.6 ) 1.7 (840.5 ) Impairment of Northern Pass Transmission — — (239.6 ) — — — (239.6 ) Other Operating Expenses (4,166.8 ) (620.4 ) (366.9 ) (75.4 ) (719.8 ) 1,708.2 (4,241.1 ) Operating Income $ 642.8 $ 103.5 $ 243.4 $ 53.1 $ 1.7 $ 110.4 $ 1,154.9 Interest Expense $ (153.3 ) $ (35.4 ) $ (94.5 ) $ (26.2 ) $ (130.3 ) $ 40.0 $ (399.7 ) Other Income, Net 44.2 1.1 78.2 0.2 813.7 (833.6 ) 103.8 Net Income Attributable to Common Shareholders 422.7 57.6 138.4 26.3 697.2 (683.2 ) 659.0 Cash Flows Used for Investments in Plant 861.0 327.8 686.7 79.9 173.6 — 2,129.0 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, 2020 $ 23,864.7 $ 4,579.9 $ 11,469.7 $ 2,332.0 $ 22,230.1 $ (20,969.1 ) $ 43,507.3 As of December 31, 2019 22,541.9 4,345.5 10,904.0 2,351.7 20,469.6 (19,488.8 ) 41,123.9

ACQUISITION OF ASSETS OF COLUMB

ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS	ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS On October 9, 2020, Eversource acquired certain assets that comprised NiSource’s local natural gas distribution business in Massachusetts, which was previously doing business as CMA, pursuant to an asset purchase agreement (the Agreement) entered into on February 26, 2020 between Eversource and NiSource Inc. The cash purchase price was $1.1 billion plus a target working capital amount, which is subject to adjustment to reflect actual working capital as of the closing date. Eversource financed the asset acquisition through a combination of debt and equity issuances in a ratio that was consistent with our consolidated capital structure. The natural gas distribution assets acquired from CMA were assigned to Eversource Gas Company of Massachusetts, an indirect wholly-owned subsidiary of Eversource formed in 2020. The LNG assets acquired from CMA were assigned to Hopkinton LNG Corp. Eversource Gas Company of Massachusetts distributes natural gas to approximately 330,000 residential, commercial and industrial customers with over 5,000 miles of natural gas distribution pipeline across more than 60 communities in Massachusetts, adding to the approximately 300,000 natural gas customers that Eversource already serves in Massachusetts. The transaction was approved by the DPU, the Maine Public Utilities Commission, the FERC, and the Federal Communications Commission. The relevant review period under the Hart-Scott-Rodino Act expired. On October 7, 2020, the DPU also approved a rate settlement with the Massachusetts Attorney General’s Office, the DOER, and the Low-Income Weatherization and Fuel Assistance Program Network. The liabilities assumed by Eversource under the Agreement specifically excluded any liabilities (past or future) arising out of, or related to, the fires and explosions that occurred on September 13, 2018 in Lawrence, Andover and North Andover, Massachusetts related to the delivery of natural gas by CMA, including certain subsequent events, all as described and in the DPU's Order on Scope dated December 23, 2019 (D.P.U. 19-141) (the Greater Lawrence Incident or GLI). The liabilities assumed also excluded any further emergency events prior to the closing of the acquisition related to the restoration and reconstruction with respect to the GLI, including any losses arising out of, or related to, any litigation, demand, cause of action, claim, suit, investigation, proceeding, indemnification agreements or rights. Eversource did not assume any of CMA's or NiSource Inc.'s debt obligations or notes payable.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	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, NSTAR Gas and Eversource Gas Company of Massachusetts (natural gas utilities) and Aquarion (water utilities). Eversource provides energy delivery and/or water service to approximately 4.3 million electric, natural gas and water customers through nine regulated utilities in Connecticut, Massachusetts and New Hampshire. On October 9, 2020, Eversource completed the acquisition of certain assets that comprised NiSource’s local natural gas distribution business in Massachusetts, which was previously doing business as Columbia Gas of Massachusetts (CMA). The natural gas distribution assets acquired from CMA were assigned to Eversource Gas Company of Massachusetts, an indirect wholly-owned subsidiary of Eversource formed in 2020. The LNG assets acquired from CMA were assigned to Hopkinton LNG Corp. The cash purchase price was $1.1 billion plus a target working capital amount, which is subject to adjustment to reflect actual working capital as of the closing date. See Note 17, "Acquisition of Assets of Columbia Gas of Massachusetts," for further information. 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 2019 Form 10-K, which was filed with the SEC on February 27, 2020. 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, 2020 and December 31, 2019 , and the results of operations, comprehensive income and common shareholders' equity for the three and nine months ended September 30, 2020 and 2019 , and the cash flows for the nine months ended September 30, 2020 and 2019 . The results of operations and comprehensive income for the three and nine months ended September 30, 2020 and 2019 and the cash flows for the nine months ended September 30, 2020 and 2019 are not necessarily indicative of the results expected for a full year. Eversource consolidates the operations of CYAPC and YAEC, both of which are inactive regional nuclear power companies engaged in the long-term storage of their spent nuclear fuel. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership and voting interests 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 holds several equity ownership interests that are not consolidated and are accounted for under the equity method. Eversource's utility subsidiaries' electric, natural gas and water distribution and transmission businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. COVID-19 has adversely affected workers and the economy and caused volatility in the financial markets. Due to the inherent uncertainty of the unprecedented and evolving situation, we continue to closely monitor how COVID-19 related developments affect Eversource. As of the date of our filing and based on available information, we have not experienced significant impacts directly related to the pandemic that have adversely affected our current operations, financial position, results of operations, and cash flows. The extent of the impact to us in the future will vary and depend in large part on the duration, scope and severity of the pandemic and the timing and extent of COVID-19 relief legislation, and the resulting impact on economic, health care and capital market conditions. The future impact will also depend on the outcome of planned proceedings before our state regulatory commissions to recover our incremental costs associated with COVID-19. We believe that we have in place, or are developing, successful mechanisms with our state regulatory commissions that allow, or will allow, us to recover our incremental costs associated with COVID-19, which include uncollectible customer receivable expenses, while balancing the impact on our customers’ bills and our operating cash flows. See Note 1C, "Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts," for discussion of our evaluation of the allowance for doubtful accounts as of September 30, 2020 in light of the COVID-19 pandemic. An extended economic slowdown has resulted in lower demand for electricity, natural gas and/or water by our commercial and industrial customers. However, fluctuations in retail sales volumes for CL&P, NSTAR Electric, Yankee Gas, NSTAR Gas, Eversource Gas Company of Massachusetts, and our Connecticut water distribution business do not materially impact earnings due to their respective state regulatory commission-approved distribution revenue decoupling mechanisms. As of September 30, 2020 , we did not identify indicators or triggering events for impairments to our goodwill, long-lived assets, available-for-sale debt securities, or equity method investment carrying values. Certain reclassifications of prior period data were made in the accompanying financial statements to conform to the current period presentation.
Accounting Standards	Accounting Standards Accounting Standards Issued but Not Yet Effective: In December 2019, the FASB issued Accounting Standards Update (ASU) 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the general principles of current income tax guidance in ASC 740 and simplifies and improves consistency in application of that income tax guidance through clarifications of and amendments to ASC 740. The guidance is effective in the first quarter of 2021. The ASU is not expected to have a material impact on the financial statements of Eversource, CL&P, NSTAR Electric and PSNH. Accounting Standards Recently Adopted: On January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), which provides a model for recognizing credit losses on financial instruments based on an estimate of current expected losses, requiring immediate recognition of credit losses expected over the life of a financial instrument. The Company determined the impacts of this standard on the allowance for credit losses on its financial instruments, primarily accounts receivable. As of January 1, 2020, the Company recorded increases to the allowance for uncollectible accounts for late fees and other receivable amounts of $1.6 million , $0.9 million , $0.2 million and $0.3 million at Eversource, CL&P, NSTAR Electric and PSNH, respectively. The impact to retained earnings, net of tax, was $1.5 million , $0.9 million , $0.2 million and $0.3 million at Eversource, CL&P, NSTAR Electric and PSNH, respectively. The Company also adjusted the allowance for uncollectible amounts of hardship receivables and other low-income assistance programs, which are ultimately collectible in rates at specified points in time under approved regulatory mechanisms. The impact on the allowance, which was offset in other long-term assets on the balance sheets, was an increase of $22.2 million and $21.3 million at Eversource and CL&P, respectively, and a decrease of $1.5 million at NSTAR Electric. See Note 1C, “Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts,” for further information. The Company adopted ASU 2017-04, Intangibles - Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment as of January 1, 2020 . The ASU simplified the accounting for goodwill impairment by removing a complex step in the goodwill impairment test. Under the guidance, goodwill impairment is measured as the amount by which its carrying value exceeds its fair value. The ASU is not expected to have an impact on the financial statements of Eversource. On January 1, 2020, the Company adopted ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The ASU aligned the requirements for capitalizing costs incurred to implement a cloud computing arrangement with existing internal-use software guidance. The prospective implementation of this standard did not have any impact on the financial statements of Eversource, CL&P, NSTAR Electric or PSNH for the period ending September 30, 2020 . On January 1, 2020, the Company prospectively adopted ASU 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement . The ASU modified fair value disclosure requirements . The standard includes new disclosure requirements for Level 3 unobservable inputs and eliminated the requirement to disclose certain information relating to transfers between levels. The modified disclosures are included in Note 1D, “Summary of Significant Accounting Policies - Fair Value Measurements,” and Note 4, “Derivative Instruments.”
Allowance for Uncollectible Accounts	Allowance for Uncollectible Accounts Receivables, Net on the balance sheets primarily i ncludes trade receivables from retail customers and customers related to wholesale transmission contracts, wholesale market sales, sales of RECs and property rentals. Receivables, Net also includes customer receivables for the purchase of electricity from a competitive third party supplier, the current portion of customer energy efficiency loans, property damage receivables and other miscellaneous receivables. There is no material concentration of receivables. Receivables are recorded at amortized cost, net of a credit loss provision (or allowance for uncollectible accounts). Receivables are presented net of expected credit losses at estimated net realizable value by maintaining an allowance for uncollectible accounts. Effective January 1, 2020, the current expected credit loss (CECL) model was applied to receivables for purposes of calculating the allowance for uncollectible accounts. This model is based on expected losses and results in the recognition of estimated expected credit losses, including uncollectible amounts for both billed and unbilled revenues, over the life of the receivable at the time a receivable is recorded. The allowance for uncollectible accounts is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. Factors in determining credit loss include historical collection, write-off experience, and management's assessment of collectibility from customers, including current conditions, reasonable forecasts, and expectations of future collectibility and collection efforts. Management continuously assesses the collectibility of receivables and adjusts estimates based on actual experience and future expectations based on economic indicators, collection efforts and other factors. Management also monitors the aging analysis of receivables to determine if there are changes in the collections of accounts receivable. Receivable balances are written off against the allowance for uncollectible accounts when the customer accounts are no longer in service and these balances are deemed to be uncollectible. As of September 30, 2020 , management evaluated the adequacy of the allowance for uncollectible accounts in light of the COVID-19 pandemic and the related economic downturn. This evaluation included an analysis of collection and customer payment trends in 2020, economic conditions, flexible payment plans and financial hardship arrearage management programs being offered to customers, and the impacts of federal governmental pandemic relief programs for our customers and the expansion of unemployment benefit initiatives, which help to mitigate the potential for increasing customer account delinquencies. Additionally, management considered past economic declines and corresponding uncollectible reserves as part of the current assessment. This evaluation has shown that our operating companies have experienced an increase in aged receivables and some lower cash collections from customers because of the moratorium on disconnections and the economic slowdown resulting from the COVID-19 pandemic. Based upon the evaluation performed, for the three and nine months ended September 30, 2020, management increased the allowance for uncollectible costs incurred as a result of COVID-19 by $11.3 million and $16.5 million for Eversource, respectively ( $2.8 million for CL&P for both periods, $5.1 million for NSTAR Electric for both periods, and $1.5 million for PSNH for both periods). These COVID-19 related uncollectible amounts were deferred either as incremental regulatory costs or deferred through existing regulatory tracking mechanisms that recover uncollectible energy supply costs as management believes it is probable that these costs will ultimately be recovered from customers in rates. Management concluded that the reserve balance as of September 30, 2020 adequately reflected the collection risk and net realizable value for Eversource’s receivables. Management will continue to evaluate the adequacy of the uncollectible allowance in future reporting periods based on an ongoing assessment of accounts receivable collections, delinquency statistics, and analysis of aging-based quantitative assessments. 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. Hardship customers are protected from shut-off in certain circumstances, and historical collection experience has reflected a higher default risk as compared to the rest of the receivable population. As a result of the adoption of ASU 2016-13, management aligned the allowance for uncollectible hardship accounts across all regulatory jurisdictions, using a higher credit risk profile for this pool of trade receivables as compared to non-hardship receivables. Implementation impacts of the accounting standard on the allowance for uncollectible hardship accounts are reflected in the rollforward of the uncollectible allowance in the table below. The allowance for uncollectible hardship accounts is included in the total uncollectible allowance balance.
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, long-lived assets 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. The 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. Uncategorized - Investments that are measured at net asset value are not categorized within the fair value hierarchy.
Other Taxes	Separate from above was an amount recorded as Taxes Other Than Income Taxes at CL&P related to the remittance to the State of Connecticut of energy efficiency funds collected from customers of $21.4 million for the nine months ended September 30, 2019. Energy efficiency funds collected from customers after July 1, 2019 are no longer subject to remittance to the State of Connecticut. This amount was recorded separately, with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the Eversource and CL&P statements of income. 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.
Restricted Cash	Special Deposits represent cash collections related to the PSNH RRB customer charges that are held in trust, required ISO-NE cash deposits, and CYAPC and YAEC cash balances. Special Deposits are included in Current Assets on the balance sheets. Restricted cash included in Marketable Securities 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 storage obligations.
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 and the equity forward sale agreement, as if they were converted into outstanding common shares. The dilutive effect of unvested RSU and performance share awards, as well as the equity forward sale agreement, 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. As described in Note 12, "Common Shares," earnings per share dilution, if any, related to the forward sale agreement is determined under the treasury stock method until settlement of the forward sale agreement. Under this method, the number of Eversource common shares used in calculating diluted EPS is deemed to be increased by the excess, if any, of the number of shares that would be issued upon physical settlement of the forward sale agreement less the number of shares that would be purchased by Eversource in the market (based on the average market pri ce during the same reporting period) using the proceeds receivable upon settlement (based on the adjusted forward sale price at the end of that reporting period). Share dilution occurs when the average market price of Eversource's common shares is higher than the adjusted forward sale price.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Allowance for Uncollectible Accounts	The activity in the allowance for uncollectible accounts by portfolio segment is as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Hardship Accounts Retail (Non-Hardship), Wholesale, and Other Receivables Total Allowance Hardship Accounts Retail (Non-Hardship), Wholesale and Other Receivables Total Allowance Hardship Accounts Retail (Non-Hardship), Wholesale, and Other Receivables Total Allowance Total Allowance Three Months Ended Beginning Balance $ 175.5 $ 94.5 $ 270.0 $ 116.3 $ 20.4 $ 136.7 $ 34.6 $ 34.1 $ 68.7 $ 11.8 Uncollectible Expense (1) — 10.5 10.5 — 3.8 3.8 — 4.5 4.5 0.8 Uncollectible Costs Deferred (2) 10.1 20.4 30.5 11.2 4.9 16.1 (1.3 ) 10.4 9.1 3.2 Write-Offs (7.3 ) (11.8 ) (19.1 ) (2.6 ) (4.6 ) (7.2 ) (0.2 ) (6.3 ) (6.5 ) (2.0 ) Recoveries Collected 0.4 2.7 3.1 0.3 1.1 1.4 — 1.0 1.0 0.2 Ending Balance $ 178.7 $ 116.3 $ 295.0 $ 125.2 $ 25.6 $ 150.8 $ 33.1 $ 43.7 $ 76.8 $ 14.0 Nine Months Ended Beginning Balance $ 143.3 $ 81.5 $ 224.8 $ 80.1 $ 17.2 $ 97.3 $ 43.9 $ 31.5 $ 75.4 $ 10.5 ASU 2016-13 Implementation Impact on January 1, 2020 21.6 2.2 23.8 21.3 0.9 22.2 (1.6 ) 0.3 (1.3 ) 0.3 Uncollectible Expense (1) — 31.1 31.1 — 10.0 10.0 — 11.3 11.3 2.1 Uncollectible Costs Deferred (2) 24.9 41.5 66.4 32.7 8.3 41.0 (8.4 ) 17.3 8.9 5.6 Write-Offs (12.3 ) (49.3 ) (61.6 ) (10.0 ) (14.0 ) (24.0 ) (0.8 ) (20.5 ) (21.3 ) (5.0 ) Recoveries Collected 1.2 9.3 10.5 1.1 3.2 4.3 — 3.8 3.8 0.5 Ending Balance $ 178.7 $ 116.3 $ 295.0 $ 125.2 $ 25.6 $ 150.8 $ 33.1 $ 43.7 $ 76.8 $ 14.0 (1) Uncollectible expense associated with customer and other accounts receivable is included in Operations and Maintenance expense on the statements of income. For the three and nine months ended September 30, 2019 , uncollectible expense included in Operations and Maintenance Expense was $14.9 million and $46.4 million for Eversource, $4.5 million and $12.1 million for CL&P, $7.0 million and $18.6 million for NSTAR Electric and $1.8 million and $5.0 million for PSNH, respectively. (2) The current period provision for expected credit losses is deferred as a regulatory cost on the balance sheets, as this amount is ultimately recovered in rates. Amounts include uncollectible costs for hardship accounts and other customer receivables, including uncollectible amounts related to COVID-19.
Components 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, 2020 September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components $ 11.0 $ 0.9 $ 7.2 $ 1.8 $ 10.1 $ 1.7 $ 5.6 $ 1.4 AFUDC Equity 10.3 3.5 5.5 0.9 10.5 3.6 5.6 1.0 Equity in Earnings of Unconsolidated Affiliates (1) 3.9 — 0.1 — 6.1 — 0.2 — Investment Income/(Loss) 1.0 1.3 (0.2 ) 0.2 (2.8 ) (0.8 ) (0.9 ) (0.3 ) Interest Income 1.5 0.2 0.1 1.2 2.9 0.3 0.1 2.5 Gain on Sale of Property 1.5 — — — — — — — Other — — 0.1 — 0.2 — 0.1 — Total Other Income, Net $ 29.2 $ 5.9 $ 12.8 $ 4.1 $ 27.0 $ 4.8 $ 10.7 $ 4.6 For the Nine Months Ended September 30, 2020 September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service Income Components $ 34.3 $ 3.0 $ 22.2 $ 5.2 $ 23.2 $ 0.1 $ 18.0 $ 3.5 AFUDC Equity 31.8 11.4 15.8 3.5 34.5 9.4 14.7 2.1 Equity in Earnings of Unconsolidated Affiliates (1) 13.8 — 0.4 — 37.0 0.2 0.6 — Investment (Loss)/Income (1.5 ) — (1.5 ) 0.1 (2.3 ) 0.9 (1.5 ) — Interest Income 3.3 1.8 0.7 2.0 10.8 1.1 0.5 9.0 Gain on Sale of Property 1.8 — 0.3 — 0.2 — — — Other 0.1 0.1 0.3 0.1 0.4 (0.1 ) 0.2 — Total Other Income, Net $ 83.6 $ 16.3 $ 38.2 $ 10.9 $ 103.8 $ 11.6 $ 32.5 $ 14.6 (1) Equity in Earnings of Unconsolidated Affiliates includes $2.4 million of primarily realized gains associated with an investment in a renewable energy fund for the nine months ended September 30, 2020 . For the nine months ended September 30, 2019 , unrealized gains on this investment totaled $20.4 million .
Other Taxes	These gross receipts taxes are recorded 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, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Eversource $ 48.4 $ 42.6 $ 129.1 $ 124.0 CL&P 45.6 39.8 114.2 107.8
Non-cash Investing Activities	Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of September 30, 2020 As of September 30, 2019 Eversource $ 357.4 $ 317.8 CL&P 97.8 107.6 NSTAR Electric 92.6 79.0 PSNH 50.0 35.8
Reconciliation of Cash Balances to Cash and Restricted Cash	The following table reconciles cash and cash equivalents as reported on the balance sheets to the cash, cash equivalents and restricted cash balance as reported on the statements of cash flows: As of September 30, 2020 As of December 31, 2019 (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 $ 730.0 $ 8.2 $ 0.1 $ 0.8 $ 15.4 $ — $ 0.1 $ 0.4 Restricted cash included in: Special Deposits 51.3 8.6 12.2 19.1 52.5 4.6 6.2 32.5 Marketable Securities 45.6 0.4 0.1 0.6 46.0 0.4 — 0.6 Other Long-Term Assets 2.1 — — 2.1 3.2 — — 3.2 Cash, Cash Equivalents and Restricted Cash as reported on the Statements of Cash Flows $ 829.0 $ 17.2 $ 12.4 $ 22.6 $ 117.1 $ 5.0 $ 6.3 $ 36.7

REGULATORY ACCOUNTING (Tables)

REGULATORY ACCOUNTING (Tables)	9 Months Ended
	Sep. 30, 2020
Regulated Operations [Abstract]
Components of Regulatory Assets	The components of regulatory assets were as follows: As of September 30, 2020 As of December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Benefit Costs $ 2,256.1 $ 483.3 $ 601.4 $ 205.7 $ 2,382.9 $ 539.0 $ 629.8 $ 218.2 Income Taxes, Net 731.2 459.8 110.0 13.7 725.8 458.8 108.0 12.8 Securitized Stranded Costs 532.9 — — 532.9 565.3 — — 565.3 Storm Restoration Costs, Net 739.6 510.7 171.4 57.5 540.6 274.6 200.6 65.4 Regulatory Tracker Mechanisms 531.8 174.4 203.0 82.3 411.5 78.3 207.1 65.8 Derivative Liabilities 311.8 311.8 — — 334.5 329.2 — — Goodwill-related 318.9 — 273.8 — 331.5 — 284.6 — Asset Retirement Obligations 105.8 32.3 56.2 3.8 97.2 30.8 50.3 3.6 Other Regulatory Assets 118.0 34.2 56.9 16.5 125.4 25.2 55.2 14.7 Total Regulatory Assets 5,646.1 2,006.5 1,472.7 912.4 5,514.7 1,735.9 1,535.6 945.8 Less: Current Portion 762.9 273.8 278.6 103.6 651.1 178.6 285.6 84.1 Total Long-Term Regulatory Assets $ 4,883.2 $ 1,732.7 $ 1,194.1 $ 808.8 $ 4,863.6 $ 1,557.3 $ 1,250.0 $ 861.7
Components of Regulatory Liabilities	The components of regulatory liabilities were as follows: As of September 30, 2020 As of December 31, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH EDIT due to Tax Cuts and Jobs Act $ 2,805.3 $ 1,013.9 $ 1,050.1 $ 388.7 $ 2,844.6 $ 1,022.8 $ 1,071.2 $ 392.8 Cost of Removal 610.4 93.0 354.8 12.9 559.8 64.6 330.6 16.3 Benefit Costs 79.5 — 68.7 — 84.5 — 72.2 — Regulatory Tracker Mechanisms 445.7 171.1 181.9 56.2 325.1 94.8 165.6 57.0 AFUDC - Transmission 77.1 45.0 32.1 — 73.2 46.0 27.2 — Other Regulatory Liabilities 158.2 38.2 57.9 9.9 132.0 19.6 59.0 13.1 Total Regulatory Liabilities 4,176.2 1,361.2 1,745.5 467.7 4,019.2 1,247.8 1,725.8 479.2 Less: Current Portion 464.7 164.9 210.7 61.5 361.2 82.8 209.2 65.8 Total Long-Term Regulatory Liabilities $ 3,711.5 $ 1,196.3 $ 1,534.8 $ 406.2 $ 3,658.0 $ 1,165.0 $ 1,516.6 $ 413.4

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Summary of Property, Plant, and Equipment	The following tables summarize property, plant and equipment by asset category: Eversource As of September 30, 2020 As of December 31, 2019 (Millions of Dollars) Distribution - Electric $ 16,435.4 $ 15,880.0 Distribution - Natural Gas 4,073.0 3,931.1 Transmission - Electric 11,601.7 10,958.4 Distribution - Water 1,683.8 1,726.5 Solar 201.2 200.2 Utility 33,995.1 32,696.2 Other (1) 1,193.0 1,025.6 Property, Plant and Equipment, Gross 35,188.1 33,721.8 Less: Accumulated Depreciation Utility (7,731.0 ) (7,483.5 ) Other (455.2 ) (387.4 ) Total Accumulated Depreciation (8,186.2 ) (7,870.9 ) Property, Plant and Equipment, Net 27,001.9 25,850.9 Construction Work in Progress 2,091.1 1,734.6 Total Property, Plant and Equipment, Net $ 29,093.0 $ 27,585.5 As of September 30, 2020 As of December 31, 2019 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Distribution - Electric $ 6,728.7 $ 7,414.0 $ 2,332.9 $ 6,485.5 $ 7,163.7 $ 2,271.1 Transmission - Electric 5,299.0 4,608.9 1,689.0 5,043.0 4,411.9 1,498.7 Solar — 201.2 — — 200.2 — Property, Plant and Equipment, Gross 12,027.7 12,224.1 4,021.9 11,528.5 11,775.8 3,769.8 Less: Accumulated Depreciation (2,453.1 ) (3,022.7 ) (832.8 ) (2,385.7 ) (2,895.3 ) (799.9 ) Property, Plant and Equipment, Net 9,574.6 9,201.4 3,189.1 9,142.8 8,880.5 2,969.9 Construction Work in Progress 490.7 742.0 130.4 483.0 592.3 159.6 Total Property, Plant and Equipment, Net $ 10,065.3 $ 9,943.4 $ 3,319.5 $ 9,625.8 $ 9,472.8 $ 3,129.5 (1) These assets are primarily comprised of computer software, hardware and equipment at Eversource Service and buildings at The Rocky River Realty Company.

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Fair Values and Net Amounts of Contracts	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, 2020 As of December 31, 2019 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Management Netting (1) Net Amount Recorded as a Derivative Commodity Supply and Price Risk Netting (1) Net Amount Recorded as a Derivative Current Derivative Assets: CL&P Level 3 $ 13.5 $ (0.4 ) $ 13.1 $ 12.2 $ (0.4 ) $ 11.8 Other Level 2 3.4 (0.7 ) 2.7 — — — Long-Term Derivative Assets: CL&P Level 3 59.1 (1.9 ) 57.2 67.5 (2.1 ) 65.4 Current Derivative Liabilities: CL&P Level 3 (69.2 ) — (69.2 ) (67.8 ) — (67.8 ) Other Level 2 — — — (5.2 ) — (5.2 ) Long-Term Derivative Liabilities: CL&P Level 3 (312.9 ) — (312.9 ) (338.6 ) — (338.6 ) Other Level 2 — — — (0.1 ) — (0.1 ) (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.
Summary of Level 3 Derivative Contracts and Significant Unobservable Inputs Used	The following is a summary of 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, 2020 As of December 31, 2019 CL&P Range Weighted Average (1) Period Covered Range Period Covered Capacity Prices $ 4.30 — $5.12 $ 4.57 per kW-Month 2024 - 2026 $ 3.01 — $7.34 per kW-Month 2023 - 2026 Forward Reserve Prices 0.54 — 0.90 0.72 per kW-Month 2021 - 2024 0.80 — 1.90 per kW-Month 2020 - 2024 (1) Unobservable inputs were weighted by the relative future capacity and forward reserve prices and contractual MWs over the periods covered.
Changes in the Level 3 Category of Derivative Assets Measured at Fair Value on a Recurring Basis	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) 2020 2019 2020 2019 Derivatives, Net: Fair Value as of Beginning of Period $ (322.0 ) $ (345.4 ) $ (329.2 ) $ (356.5 ) Net Realized/Unrealized Losses Included in Regulatory Assets (4.7 ) (8.5 ) (22.3 ) (16.4 ) Settlements 14.9 11.6 39.7 30.6 Fair Value as of End of Period $ (311.8 ) $ (342.3 ) $ (311.8 ) $ (342.3 )

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Summary of 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, 2020 As of December 31, 2019 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 $ 216.1 $ 11.1 $ (0.2 ) $ 227.0 $ 228.4 $ 5.8 $ (0.1 ) $ 234.1
Contractual Maturities of Available-for-Sale Debt Securities	As of September 30, 2020 , 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) $ 51.1 $ 51.1 One to five years 45.2 47.4 Six to ten years 43.9 47.0 Greater than ten years 75.9 81.5 Total Debt Securities $ 216.1 $ 227.0 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC spent nuclear fuel trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets.
Marketable Securities Recorded at Fair Value on a Recurring Basis by Level	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, 2020 As of December 31, 2019 Level 1: Mutual Funds and Equities $ 226.3 $ 228.5 Money Market Funds 45.6 46.0 Total Level 1 $ 271.9 $ 274.5 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 64.7 $ 96.8 Corporate Debt Securities 64.9 44.0 Asset-Backed Debt Securities 12.0 12.9 Municipal Bonds 30.4 26.7 Other Fixed Income Securities 9.4 7.7 Total Level 2 $ 181.4 $ 188.1 Total Marketable Securities $ 453.3 $ 462.6

SHORT-TERM AND LONG-TERM DEBT (

SHORT-TERM AND LONG-TERM DEBT (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Borrowings Outstanding and Available under the Commecrial Paper Programs	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, 2020 December 31, 2019 September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 (Millions of Dollars) Eversource Parent Commercial Paper Program $ — $ 1,224.9 $ 1,450.0 $ 225.1 — % 1.98 % NSTAR Electric Commercial Paper Program 60.5 10.5 589.5 639.5 0.10 % 1.63 %
Summary of Long-Term Debt Issuance and Repayments	The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issuance/(Repayment) Issue Date or Repayment Date Maturity Date Use of Proceeds for Issuance/ NSTAR Electric: 3.95% 2020 Debentures $ 400.0 March 2020 April 2030 Refinanced investments in eligible green expenditures, which were previously financed in 2018 and 2019 5.10% Series E Senior Notes (95.0 ) March 2020 March 2020 Paid at maturity PSNH: 2.40% Series U First Mortgage Bonds 150.0 August 2020 September 2050 Refinanced short-term borrowings, funded capital expenditures and working capital Other: Eversource Parent 3.45% Series P Senior Notes 350.0 January 2020 January 2050 Paid short-term borrowings Eversource Parent 3.45% Series P Senior Notes (1) 300.0 August 2020 January 2050 (2) Eversource Parent 0.80% Series Q Senior Notes 300.0 August 2020 August 2025 (2) Eversource Parent 1.65% Series R Senior Notes 600.0 August 2020 August 2030 (2) NSTAR Gas 4.46% Series N First Mortgage Bonds (125.0 ) January 2020 January 2020 Paid at maturity NSTAR Gas 2.33% Series R First Mortgage Bonds 75.0 May 2020 May 2025 Refinanced existing indebtedness, funded capital expenditures and for general corporate purposes NSTAR Gas 3.15% Series S First Mortgage Bonds 115.0 May 2020 May 2050 Refinanced existing indebtedness, funded capital expenditures and for general corporate purposes Yankee Gas 4.87% Series K First Mortgage Bonds (50.0 ) April 2020 April 2020 Paid at maturity Yankee Gas 2.90% Series R First Mortgage Bonds 70.0 September 2020 September 2050 Refinanced existing indebtedness, funded capital expenditures and for general corporate purposes Aquarion Water Company of Massachusetts, Inc. and Aquarion Water Capital of Massachusetts, Inc. various term loans and general mortgage bonds (32.2 ) July 2020 Various Redeemed long-term debt in conjunction with the sale of assets to the Town of Hingham, Massachusetts (1) These senior notes are part of the same series issued by Eversource parent in January 2020. The aggregate outstanding principal amount of these senior notes is now $650 million . (2) The proceeds from these Eversource parent issuances funded a portion of the purchase price for the CMA asset acquisition and refinanced short-term borrowings.

RATE REDUCTION BONDS AND VARI_2

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES (Tables)	9 Months Ended
	Sep. 30, 2020
Rate Reduction Bonds and Variable Interest Entity [Abstract]
Summary of the Impact of Funding on the Balance Sheets and Income Statements	The following tables summarize the impact of PSNH Funding on PSNH's balance sheets and income statements: (Millions of Dollars) Balance Sheet: As of September 30, 2020 As of December 31, 2019 Restricted Cash - Current Portion (included in Current Assets) $ 18.8 $ 32.5 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 2.1 3.2 Securitized Stranded Cost (included in Regulatory Assets) 532.9 565.3 Other Regulatory Liabilities (included in Regulatory Liabilities) 7.2 5.6 Accrued Interest (included in Other Current Liabilities) 3.2 8.6 Rate Reduction Bonds - Current Portion 43.2 43.2 Rate Reduction Bonds - Long-Term Portion 496.9 540.1 (Millions of Dollars) Income Statement: For the Three Months Ended For the Nine Months Ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 10.8 $ 10.8 $ 32.4 $ 32.2 Interest Expense on RRB Principal (included in Interest Expense) 4.9 5.2 14.9 15.9

PENSION BENEFITS AND POSTRETI_2

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION (Tables)	9 Months Ended
	Sep. 30, 2020
Postemployment Benefits [Abstract]
Components of Net Periodic Benefit Expense/(Income)	The components of net periodic benefit expense/(income) for the Pension, SERP and PBOP Plans, prior to amounts capitalized as Property, Plant and Equipment or deferred as regulatory assets for future recovery, are shown below. The service cost component of net periodic benefit expense/(income), less the capitalized portion, is included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit expense/(income), less the deferred portion, are included in Other Income, Net on the statements of income. 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 PBOP For the Three Months Ended September 30, 2020 For the Three Months Ended September 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 18.7 $ 5.4 $ 3.8 $ 2.0 $ 2.4 $ 0.4 $ 0.5 $ 0.2 Interest Cost 44.4 9.3 9.7 4.8 6.1 1.1 1.7 0.7 Expected Return on Plan Assets (99.2 ) (19.8 ) (25.7 ) (11.1 ) (18.3 ) (2.5 ) (8.5 ) (1.4 ) Actuarial Loss 50.7 9.7 14.0 3.8 2.2 0.3 0.6 0.2 Prior Service Cost/(Credit) 0.2 — — — (5.3 ) 0.3 (4.2 ) 0.1 Total Net Periodic Benefit Expense/(Income) $ 14.8 $ 4.6 $ 1.8 $ (0.5 ) $ (12.9 ) $ (0.4 ) $ (9.9 ) $ (0.2 ) Intercompany Allocations N/A $ 2.4 $ 2.3 $ 0.8 N/A $ (0.3 ) $ (0.4 ) $ (0.1 ) Pension and SERP PBOP For the Nine Months Ended September 30, 2020 For the Nine Months Ended September 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 57.0 $ 16.5 $ 11.4 $ 6.2 $ 7.3 $ 1.3 $ 1.6 $ 0.6 Interest Cost 133.0 28.1 29.0 14.5 18.3 3.3 5.0 2.1 Expected Return on Plan Assets (298.8 ) (59.6 ) (77.2 ) (33.5 ) (55.1 ) (7.4 ) (25.5 ) (4.2 ) Actuarial Loss 150.7 29.4 41.3 11.8 6.3 0.9 1.8 0.6 Prior Service Cost/(Credit) 0.8 — 0.2 — (15.9 ) 0.8 (12.7 ) 0.3 Total Net Periodic Benefit Expense/(Income) $ 42.7 $ 14.4 $ 4.7 $ (1.0 ) $ (39.1 ) $ (1.1 ) $ (29.8 ) $ (0.6 ) Intercompany Allocations N/A $ 6.7 $ 6.5 $ 2.2 N/A $ (0.9 ) $ (1.0 ) $ (0.4 ) Pension and SERP PBOP For the Three Months Ended September 30, 2019 For the Three Months Ended September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 16.2 $ 4.4 $ 3.6 $ 1.5 $ 2.0 $ 0.3 $ 0.4 $ 0.2 Interest Cost 54.8 11.4 12.3 6.0 8.1 1.6 2.4 0.8 Expected Return on Plan Assets (91.6 ) (18.1 ) (24.2 ) (10.1 ) (16.7 ) (2.2 ) (7.5 ) (1.3 ) Actuarial Loss 35.6 6.3 11.8 2.3 2.1 0.3 0.8 0.1 Prior Service Cost/(Credit) 0.3 — — — (5.8 ) 0.2 (4.2 ) 0.1 Total Net Periodic Benefit Expense/(Income) $ 15.3 $ 4.0 $ 3.5 $ (0.3 ) $ (10.3 ) $ 0.2 $ (8.1 ) $ (0.1 ) Intercompany Allocations N/A $ 2.0 $ 1.9 $ 0.5 N/A $ (0.2 ) $ (0.3 ) $ (0.1 ) Pension and SERP PBOP For the Nine Months Ended September 30, 2019 For the Nine Months Ended September 30, 2019 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 51.6 $ 13.6 $ 11.0 $ 5.6 $ 5.9 $ 1.1 $ 1.3 $ 0.5 Interest Cost 163.8 34.4 36.6 18.2 24.5 4.7 7.1 2.5 Expected Return on Plan Assets (275.4 ) (55.1 ) (72.9 ) (30.6 ) (50.1 ) (6.9 ) (22.6 ) (4.0 ) Actuarial Loss 107.9 20.6 33.1 8.2 6.2 1.0 2.5 0.3 Prior Service Cost/(Credit) 0.9 — 0.2 — (17.6 ) 0.8 (12.7 ) 0.3 Total Net Periodic Benefit Expense/(Income) $ 48.8 $ 13.5 $ 8.0 $ 1.4 $ (31.1 ) $ 0.7 $ (24.4 ) $ (0.4 ) Intercompany Allocations N/A $ 6.5 $ 6.1 $ 1.8 N/A $ (0.6 ) $ (0.9 ) $ (0.3 )

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Environmental Sites and Related Reserves	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, 2020 As of December 31, 2019 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 55 $ 78.8 57 $ 81.0 CL&P 15 11.6 15 11.4 NSTAR Electric 13 4.6 15 8.0 PSNH 9 7.2 9 7.5
Non-Cancelable Commitments under Purchase Commitment Contracts	Renewable energy contracts include non-cancelable commitments under contracts of NSTAR Electric for the purchase of energy and RECs from renewable energy facilities. NSTAR Electric October - December 2020 (Millions of Dollars) 2021 2022 2023 2024 Thereafter Total Renewable Energy $ 24.3 $ 98.5 $ 100.0 $ 75.4 $ 72.9 $ 594.5 $ 965.6
Summary of Exposure to Guarantees and Indemnifications	The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries and affiliates to external parties as of September 30, 2020 : Company Description Maximum Exposure (in millions) Expiration Dates Various Surety Bonds (1) $ 30.9 2020 - 2023 Rocky River Realty Company and Eversource Service Lease Payments for Real Estate 5.6 2024 Bay State Wind LLC Real Estate Purchase 2.5 2021 Sunrise Wind LLC OREC Capacity Production (2) 2.2 - (1) 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. (2) On October 25, 2019, Eversource parent issued a guaranty on behalf of its 50 percent -owned affiliate, Sunrise Wind LLC, whereby Eversource parent will guaranty Sunrise Wind LLC’s performance of certain obligations, in an amount not to exceed $15.4 million , under the Offshore Wind Renewable Energy Certificate Purchase and Sale Agreement (the Agreement). The Agreement was executed on October 23, 2019, by and between the New York State Energy Research and Development Authority (NYSERDA) and Sunrise Wind LLC. The Company regularly reviews performance risk under this arrangement, and in the event it becomes probable that Eversource parent will be required to perform under the guarantee, the amount of probable payment will be recorded. As of September 30, 2020 , the fair value of the guarantee was immaterial.

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Carrying Amounts and Estimated Fair Values of Financial Instruments	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, 2020: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 166.6 $ 116.2 $ 122.0 $ 43.0 $ 44.6 $ — $ — Long-Term Debt 15,814.5 17,943.7 3,518.1 4,336.7 3,642.8 4,285.4 1,099.0 1,192.1 Rate Reduction Bonds 540.1 603.0 — — — — 540.1 603.0 As of December 31, 2019: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 162.0 $ 116.2 $ 117.8 $ 43.0 $ 44.2 $ — $ — Long-Term Debt 14,098.2 15,170.2 3,518.1 4,058.0 3,342.1 3,659.9 951.6 1,005.7 Rate Reduction Bonds 583.3 625.9 — — — — 583.3 625.9

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income/(Loss) by Component, Net of Tax	The changes in accumulated other comprehensive income/(loss) by component, net of tax, are as follows: For the Nine Months Ended September 30, 2020 For the Nine Months Ended September 30, 2019 Eversource (Millions of Dollars) Qualified Cash Flow Hedging Instruments Unrealized Gains on Marketable Securities Defined Benefit Plans Total Qualified Cash Flow Hedging Instruments Unrealized Gains/(Losses) on Marketable Securities Defined Benefit Plans Total Balance as of January 1st $ (3.0 ) $ 0.7 $ (62.8 ) $ (65.1 ) $ (4.4 ) $ (0.5 ) $ (55.1 ) $ (60.0 ) OCI Before Reclassifications — 0.3 (1.6 ) (1.3 ) — 1.3 2.6 3.9 Amounts Reclassified from AOCI 1.2 — 4.8 6.0 0.9 — 3.2 4.1 Net OCI 1.2 0.3 3.2 4.7 0.9 1.3 5.8 8.0 Balance as of September 30th $ (1.8 ) $ 1.0 $ (59.6 ) $ (60.4 ) $ (3.5 ) $ 0.8 $ (49.3 ) $ (52.0 )

COMMON SHARES (Tables)

COMMON SHARES (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Common Shares Authorized and Issued	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, 2020 and December 31, 2019 Issued as of Par Value September 30, 2020 December 31, 2019 Eversource $ 5 380,000,000 357,818,402 345,858,402 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, 2020
Earnings Per Share [Abstract]
Components of Basic and Diluted EPS	The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended For the Nine Months Ended September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Net Income Attributable to Common Shareholders $ 346.3 $ 318.9 $ 933.2 $ 659.0 Weighted Average Common Shares Outstanding: Basic 343,076,614 324,037,169 337,375,172 320,442,253 Dilutive Effect of: Share-Based Compensation Awards and Other 696,988 737,972 686,403 691,636 Equity Forward Sale Agreement — 1,233,201 362,525 437,037 Total Dilutive Effect 696,988 1,971,173 1,048,928 1,128,673 Diluted 343,773,602 326,008,342 338,424,100 321,570,926 Basic EPS $ 1.01 $ 0.98 $ 2.77 $ 2.06 Diluted EPS $ 1.01 $ 0.98 $ 2.76 $ 2.05

REVENUES (Tables)

REVENUES (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Operating Revenues Disaggregated by Revenue Source	The following tables present operating revenues disaggregated by revenue source: For the Three Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,183.9 $ 45.5 $ — $ 45.8 $ — $ — $ 1,275.2 Commercial 682.7 41.1 — 17.1 — (1.4 ) 739.5 Industrial 91.0 17.5 — 1.3 — (3.6 ) 106.2 Total Retail Tariff Sales Revenues 1,957.6 104.1 — 64.2 — (5.0 ) 2,120.9 Wholesale Transmission Revenues — — 458.2 — 19.0 (365.6 ) 111.6 Wholesale Market Sales Revenues 79.6 8.7 — 1.1 — — 89.4 Other Revenues from Contracts with Customers 18.4 0.8 3.2 1.8 303.3 (299.0 ) 28.5 Amortization of/(Reserve for) Revenues Subject to Refund 2.3 0.5 — (1.1 ) — — 1.7 Total Revenues from Contracts with Customers 2,057.9 114.1 461.4 66.0 322.3 (669.6 ) 2,352.1 Alternative Revenue Programs 1.7 (4.0 ) (72.3 ) (2.0 ) — 67.0 (9.6 ) Other Revenues (1) 0.7 0.1 0.2 0.1 — — 1.1 Total Operating Revenues $ 2,060.3 $ 110.2 $ 389.3 $ 64.1 $ 322.3 $ (602.6 ) $ 2,343.6 For the Nine Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 3,063.7 $ 399.6 $ — $ 113.2 $ — $ — $ 3,576.5 Commercial 1,815.7 243.5 — 47.7 — (3.7 ) 2,103.2 Industrial 248.4 67.0 — 3.6 — (10.1 ) 308.9 Total Retail Tariff Sales Revenues 5,127.8 710.1 — 164.5 — (13.8 ) 5,988.6 Wholesale Transmission Revenues — — 1,177.9 — 55.6 (981.4 ) 252.1 Wholesale Market Sales Revenues 231.1 31.9 — 2.9 — — 265.9 Other Revenues from Contracts with Customers 56.4 2.5 9.9 5.6 845.1 (838.0 ) 81.5 Amortization of/(Reserve for) Revenues Subject to Refund 6.9 1.6 — (2.8 ) — — 5.7 Total Revenues from Contracts with Customers 5,422.2 746.1 1,187.8 170.2 900.7 (1,833.2 ) 6,593.8 Alternative Revenue Programs 54.8 22.9 (52.7 ) (4.1 ) — 48.9 69.8 Other Revenues (1) 4.9 1.0 0.5 0.5 — — 6.9 Total Operating Revenues $ 5,481.9 $ 770.0 $ 1,135.6 $ 166.6 $ 900.7 $ (1,784.3 ) $ 6,670.5 For the Three Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,041.4 $ 43.0 $ — $ 40.0 $ — $ — $ 1,124.4 Commercial 736.6 41.6 — 17.8 — (1.4 ) 794.6 Industrial 90.6 18.1 — 1.3 — (3.2 ) 106.8 Total Retail Tariff Sales Revenues 1,868.6 102.7 — 59.1 — (4.6 ) 2,025.8 Wholesale Transmission Revenues — — 365.5 — 15.4 (300.7 ) 80.2 Wholesale Market Sales Revenues 33.1 5.5 — 1.3 — — 39.9 Other Revenues from Contracts with Customers 12.3 0.5 3.1 1.7 242.7 (243.0 ) 17.3 Amortization of/(Reserve for) Revenues 4.5 1.5 — (0.8 ) — — 5.2 Total Revenues from Contracts with Customers 1,918.5 110.2 368.6 61.3 258.1 (548.3 ) 2,168.4 Alternative Revenue Programs 6.7 (7.6 ) (20.9 ) 2.6 — 19.0 (0.2 ) Other Revenues (1) 6.4 0.8 0.1 0.3 — — 7.6 Total Operating Revenues $ 1,931.6 $ 103.4 $ 347.8 $ 64.2 $ 258.1 $ (529.3 ) $ 2,175.8 For the Nine Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 2,879.8 $ 402.0 $ — $ 100.5 $ — $ — $ 3,382.3 Commercial 2,002.0 254.9 — 48.1 — (3.4 ) 2,301.6 Industrial 254.0 72.5 — 3.5 — (8.7 ) 321.3 Total Retail Tariff Sales Revenues 5,135.8 729.4 — 152.1 — (12.1 ) 6,005.2 Wholesale Transmission Revenues — — 971.6 — 43.7 (811.4 ) 203.9 Wholesale Market Sales Revenues 123.9 41.6 — 3.2 — — 168.7 Other Revenues from Contracts with Customers 40.0 1.9 9.9 5.2 723.4 (725.2 ) 55.2 (Reserve for)/Amortization of Revenues (1.7 ) 4.7 — (1.9 ) — — 1.1 Total Revenues from Contracts with Customers 5,298.0 777.6 981.5 158.6 767.1 (1,548.7 ) 6,434.1 Alternative Revenue Programs 15.0 — 56.1 4.2 — (50.8 ) 24.5 Other Revenues (1) 14.2 2.3 0.3 0.7 — — 17.5 Total Operating Revenues $ 5,327.2 $ 779.9 $ 1,037.9 $ 163.5 $ 767.1 $ (1,599.5 ) $ 6,476.1 For the Three Months Ended September 30, 2020 For the Three Months Ended September 30, 2019 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 608.7 $ 415.4 $ 159.8 $ 513.6 $ 374.4 $ 153.4 Commercial 244.7 358.3 80.1 247.0 406.1 84.1 Industrial 38.0 30.6 22.4 37.4 32.4 20.8 Total Retail Tariff Sales Revenues 891.4 804.3 262.3 798.0 812.9 258.3 Wholesale Transmission Revenues 233.3 153.1 71.8 175.2 132.9 57.4 Wholesale Market Sales Revenues 60.0 12.1 7.5 13.8 14.4 4.9 Other Revenues from Contracts with Customers 8.1 10.5 3.7 9.0 3.1 4.0 Amortization of Revenues Subject to Refund — — 2.3 — — 4.5 Total Revenues from Contracts with Customers 1,192.8 980.0 347.6 996.0 963.3 329.1 Alternative Revenue Programs (65.0 ) 8.2 (13.8 ) (15.2 ) 9.8 (8.8 ) Other Revenues (1) 0.2 0.7 — 4.1 1.8 0.6 Eliminations (133.7 ) (113.5 ) (50.1 ) (131.0 ) (96.2 ) (40.5 ) Total Operating Revenues $ 994.3 $ 875.4 $ 283.7 $ 853.9 $ 878.7 $ 280.4 For the Nine Months Ended September 30, 2020 For the Nine Months Ended September 30, 2019 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,567.9 $ 1,057.9 $ 437.9 $ 1,426.9 $ 1,027.8 $ 425.1 Commercial 670.4 921.3 225.3 708.4 1,058.3 236.8 Industrial 105.3 82.1 61.0 105.8 90.1 58.1 Total Retail Tariff Sales Revenues 2,343.6 2,061.3 724.2 2,241.1 2,176.2 720.0 Wholesale Transmission Revenues 576.5 430.3 171.1 445.9 383.1 142.6 Wholesale Market Sales Revenues 163.9 39.8 27.4 39.6 55.9 28.4 Other Revenues from Contracts with Customers 25.1 32.4 10.9 27.0 13.2 11.8 Amortization of/(Reserve for) Revenues — — 6.9 — — (1.7 ) Total Revenues from Contracts with Customers 3,109.1 2,563.8 940.5 2,753.6 2,628.4 901.1 Alternative Revenue Programs (27.8 ) 31.1 (1.2 ) 45.6 19.1 6.4 Other Revenues (1) 2.0 2.8 0.6 7.9 5.2 1.4 Eliminations (371.9 ) (327.5 ) (124.6 ) (363.1 ) (294.5 ) (111.1 ) Total Operating Revenues $ 2,711.4 $ 2,270.2 $ 815.3 $ 2,444.0 $ 2,358.2 $ 797.8 (1) Other Revenues include certain fees charged to customers that are not considered revenue from contracts with customers. Other revenues also include lease revenues under lessor accounting guidance of $1.1 million (including $0.2 million at CL&P and $0.7 million at NSTAR Electric) and $1.2 million (including $0.3 million at CL&P and $0.7 million at NSTAR Electric) for the three months ended September 30, 2020 and 2019 , respectively, and $3.2 million (including $0.6 million at CL&P and $2.1 million at NSTAR Electric) and $3.4 million (including $0.7 million at CL&P and $2.0 million at NSTAR Electric) for the nine months ended September 30, 2020 and 2019 , respectively.

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Summary of Segment Information and Segmented Total Assets	Eversource's segment information is as follows: For the Three Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 2,060.3 $ 110.2 $ 389.3 $ 64.1 $ 322.3 $ (602.6 ) $ 2,343.6 Depreciation and Amortization (182.0 ) (14.8 ) (70.6 ) (10.8 ) (24.1 ) 0.3 (302.0 ) Other Operating Expenses (1,577.0 ) (104.2 ) (120.6 ) (10.2 ) (271.5 ) 603.1 (1,480.4 ) Operating Income/(Loss) $ 301.3 $ (8.8 ) $ 198.1 $ 43.1 $ 26.7 $ 0.8 $ 561.2 Interest Expense $ (53.3 ) $ (10.1 ) $ (31.1 ) $ (8.0 ) $ (38.7 ) $ 7.1 $ (134.1 ) Other Income, Net 16.0 0.7 6.9 1.6 387.0 (383.0 ) 29.2 Net Income/(Loss) Attributable to Common Shareholders 205.5 (14.0 ) 125.6 23.1 381.2 (375.1 ) 346.3 For the Nine Months Ended September 30, 2020 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 5,481.9 $ 770.0 $ 1,135.6 $ 166.6 $ 900.7 $ (1,784.3 ) $ 6,670.5 Depreciation and Amortization (490.0 ) (55.1 ) (206.8 ) (33.1 ) (68.1 ) 1.2 (851.9 ) Other Operating Expenses (4,309.9 ) (592.0 ) (338.5 ) (60.7 ) (771.4 ) 1,787.9 (4,284.6 ) Operating Income $ 682.0 $ 122.9 $ 590.3 $ 72.8 $ 61.2 $ 4.8 $ 1,534.0 Interest Expense $ (160.7 ) $ (32.1 ) $ (93.8 ) $ (25.1 ) $ (119.0 ) $ 27.6 $ (403.1 ) Other Income, Net 44.9 2.5 22.7 1.7 1,161.7 (1,149.9 ) 83.6 Net Income Attributable to Common Shareholders 450.6 73.8 381.8 35.6 1,108.9 (1,117.5 ) 933.2 Cash Flows Used for Investments in Plant 781.2 322.8 732.4 84.0 181.2 — 2,101.6 For the Three Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 1,931.6 $ 103.4 $ 347.8 $ 64.2 $ 258.1 $ (529.3 ) $ 2,175.8 Depreciation and Amortization (188.4 ) (16.1 ) (64.3 ) (11.1 ) (17.2 ) 0.6 (296.5 ) Other Operating Expenses (1,448.2 ) (99.3 ) (159.6 ) (25.5 ) (275.9 ) 638.4 (1,370.1 ) Operating Income/(Loss) $ 295.0 $ (12.0 ) $ 123.9 $ 27.6 $ (35.0 ) $ 109.7 $ 509.2 Interest Expense $ (53.2 ) $ (11.7 ) $ (33.6 ) $ (8.9 ) $ (41.7 ) $ 13.9 $ (135.2 ) Other Income/(Loss), Net 13.9 — 61.4 (0.2 ) 497.0 (545.1 ) 27.0 Net Income/(Loss) Attributable to Common Shareholders 197.3 (17.1 ) 107.5 17.5 435.2 (421.5 ) 318.9 For the Nine Months Ended September 30, 2019 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 5,327.2 $ 779.9 $ 1,037.9 $ 163.5 $ 767.1 $ (1,599.5 ) $ 6,476.1 Depreciation and Amortization (517.6 ) (56.0 ) (188.0 ) (35.0 ) (45.6 ) 1.7 (840.5 ) Impairment of Northern Pass Transmission — — (239.6 ) — — — (239.6 ) Other Operating Expenses (4,166.8 ) (620.4 ) (366.9 ) (75.4 ) (719.8 ) 1,708.2 (4,241.1 ) Operating Income $ 642.8 $ 103.5 $ 243.4 $ 53.1 $ 1.7 $ 110.4 $ 1,154.9 Interest Expense $ (153.3 ) $ (35.4 ) $ (94.5 ) $ (26.2 ) $ (130.3 ) $ 40.0 $ (399.7 ) Other Income, Net 44.2 1.1 78.2 0.2 813.7 (833.6 ) 103.8 Net Income Attributable to Common Shareholders 422.7 57.6 138.4 26.3 697.2 (683.2 ) 659.0 Cash Flows Used for Investments in Plant 861.0 327.8 686.7 79.9 173.6 — 2,129.0 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, 2020 $ 23,864.7 $ 4,579.9 $ 11,469.7 $ 2,332.0 $ 22,230.1 $ (20,969.1 ) $ 43,507.3 As of December 31, 2019 22,541.9 4,345.5 10,904.0 2,351.7 20,469.6 (19,488.8 ) 41,123.9

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands, customer in Millions	Oct. 09, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)customerutility	Sep. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Jan. 01, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Summary of Accounting Policies [Line Items]
Number of electric, natural gas and water customers | customer			4.3
Allowance for uncollectible accounts for late fees and other receivable amounts		$ 295,000	$ 295,000		$ 270,000			$ 224,800
Stockholders' equity		13,980,017	13,980,017	$ 12,121,614	13,805,258	$ 13,209,956		12,629,994	$ 11,954,593	$ 11,637,434	$ 11,486,817
Adoption of new accounting standard		13,980,017	13,980,017	12,121,614	13,805,258	13,209,956		12,629,994	11,954,593	11,637,434	11,486,817
Energy efficiency funds collected from customers to be remitted to the State of Connecticut				21,400
CMA | Subsequent Event
Summary of Accounting Policies [Line Items]
Cash purchase price	$ 1,100,000
Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity		4,535,860	4,535,860	4,100,220	4,384,093	4,322,825		4,177,048	3,954,492	4,092,895	3,953,974
Adoption of new accounting standard		4,535,860	4,535,860	4,100,220	4,384,093	4,322,825		4,177,048	3,954,492	4,092,895	3,953,974
NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts		76,800	76,800		68,700			75,400
Stockholders' equity		4,325,539	4,325,539	3,915,916	4,160,236	4,063,190		4,159,884	3,751,354	3,783,196	3,730,155
Adoption of new accounting standard		4,325,539	4,325,539	3,915,916	4,160,236	4,063,190		4,159,884	3,751,354	3,783,196	3,730,155
NSTAR Electric | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity		2,511,742	2,511,742	2,253,509	2,346,504	2,249,526		2,346,287	2,099,059	2,131,015	2,098,091
Adoption of new accounting standard		2,511,742	2,511,742	2,253,509	2,346,504	2,249,526		2,346,287	2,099,059	2,131,015	2,098,091
CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts		150,800	150,800		136,700			97,300
Stockholders' equity		4,794,352	4,794,352	4,180,334	4,550,656	4,434,772		4,387,825	4,136,438	4,209,415	4,199,317
Adoption of new accounting standard		4,794,352	$ 4,794,352	4,180,334	4,550,656	4,434,772		4,387,825	4,136,438	4,209,415	4,199,317
Period of accounts receivable recoverable under financial or medical duress			180 days
CL&P | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity		2,072,928	$ 2,072,928	1,708,892	1,954,221	1,838,340		1,791,392	1,664,995	1,737,980	1,727,899
Adoption of new accounting standard		2,072,928	2,072,928	1,708,892	1,954,221	1,838,340		1,791,392	1,664,995	1,737,980	1,727,899
PSNH
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts		14,000	14,000		11,800			10,500
Stockholders' equity		1,488,340	1,488,340	1,151,934	1,440,929	1,409,012		1,391,733	1,129,777	1,316,629	1,302,541
Adoption of new accounting standard		1,488,340	1,488,340	1,151,934	1,440,929	1,409,012		1,391,733	1,129,777	1,316,629	1,302,541
PSNH | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity		586,090	586,090	475,770	538,939	507,307		490,306	453,891	641,039	627,258
Adoption of new accounting standard		586,090	$ 586,090	$ 475,770	538,939	$ 507,307		490,306	$ 453,891	$ 641,039	$ 627,258
Yankee Gas
Summary of Accounting Policies [Line Items]
Period of accounts receivable recoverable under financial or medical duress			90 days
Restatement Adjustment
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								23,800
Restatement Adjustment | NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								(1,300)
Restatement Adjustment | CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								22,200
Restatement Adjustment | PSNH
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								300
Connecticut, Massachusetts and New Hampshire
Summary of Accounting Policies [Line Items]
Number of regulated utilities | utility			9
COVID-19
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		11,300	$ 16,500
COVID-19 | NSTAR Electric
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		5,100	5,100
COVID-19 | CL&P
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		2,800	2,800
COVID-19 | PSNH
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		1,500	1,500
Adoption Adjustment
Summary of Accounting Policies [Line Items]
Stockholders' equity								(1,514)
Adoption of new accounting standard								(1,514)
Adoption Adjustment | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity							$ (1,500)	(1,514)
Adoption of new accounting standard							(1,500)	(1,514)
Adoption Adjustment | NSTAR Electric
Summary of Accounting Policies [Line Items]
Stockholders' equity								(161)
Adoption of new accounting standard								(161)
Adoption Adjustment | NSTAR Electric | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity							(200)	(161)
Adoption of new accounting standard							(200)	(161)
Adoption Adjustment | CL&P
Summary of Accounting Policies [Line Items]
Stockholders' equity								(900)
Adoption of new accounting standard								(900)
Adoption Adjustment | CL&P | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity							(900)	(900)
Adoption of new accounting standard							(900)	(900)
Adoption Adjustment | PSNH
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts							300
Stockholders' equity								(300)
Adoption of new accounting standard								(300)
Adoption Adjustment | PSNH | Retained Earnings
Summary of Accounting Policies [Line Items]
Stockholders' equity							(300)	(300)
Adoption of new accounting standard							(300)	(300)
Retail (Non-Hardship), Wholesale, and Other Receivables
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts		116,300	116,300		94,500			81,500
Retail (Non-Hardship), Wholesale, and Other Receivables | NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts		43,700	43,700		34,100			31,500
Retail (Non-Hardship), Wholesale, and Other Receivables | CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts		$ 25,600	$ 25,600		$ 20,400			17,200
Retail (Non-Hardship), Wholesale, and Other Receivables | Restatement Adjustment
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								2,200
Retail (Non-Hardship), Wholesale, and Other Receivables | Restatement Adjustment | NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								300
Retail (Non-Hardship), Wholesale, and Other Receivables | Restatement Adjustment | CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								900
Retail (Non-Hardship), Wholesale, and Other Receivables | Adoption Adjustment
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts							1,600
Retail (Non-Hardship), Wholesale, and Other Receivables | Adoption Adjustment | NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts							200
Retail (Non-Hardship), Wholesale, and Other Receivables | Adoption Adjustment | CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts							$ 900
Hardship Accounts and Other Low-Income Assistance Programs | Restatement Adjustment
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								22,200
Hardship Accounts and Other Low-Income Assistance Programs | Restatement Adjustment | NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								(1,500)
Hardship Accounts and Other Low-Income Assistance Programs | Restatement Adjustment | CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts								$ 21,300

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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 270,000		$ 224,800
Uncollectible Expense	10,500	$ 14,900	31,101	$ 46,417
Uncollectible Costs Deferred	30,500		66,400
Write-Offs	(19,100)		(61,600)
Recoveries Collected	3,100		10,500
Ending Balance	295,000		295,000
CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	136,700		97,300
Uncollectible Expense	3,800	4,500	10,013	12,084
Uncollectible Costs Deferred	16,100		41,000
Write-Offs	(7,200)		(24,000)
Recoveries Collected	1,400		4,300
Ending Balance	150,800		150,800
NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	68,700		75,400
Uncollectible Expense	4,500	7,000	11,321	18,598
Uncollectible Costs Deferred	9,100		8,900
Write-Offs	(6,500)		(21,300)
Recoveries Collected	1,000		3,800
Ending Balance	76,800		76,800
PSNH
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	11,800		10,500
Uncollectible Expense	800	$ 1,800	2,058	$ 4,977
Uncollectible Costs Deferred	3,200		5,600
Write-Offs	(2,000)		(5,000)
Recoveries Collected	200		500
Ending Balance	14,000		14,000
Hardship Accounts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	175,500		143,300
Uncollectible Expense	0		0
Uncollectible Costs Deferred	10,100		24,900
Write-Offs	(7,300)		(12,300)
Recoveries Collected	400		1,200
Ending Balance	178,700		178,700
Hardship Accounts | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	116,300		80,100
Uncollectible Expense	0		0
Uncollectible Costs Deferred	11,200		32,700
Write-Offs	(2,600)		(10,000)
Recoveries Collected	300		1,100
Ending Balance	125,200		125,200
Hardship Accounts | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	34,600		43,900
Uncollectible Expense	0		0
Uncollectible Costs Deferred	(1,300)		(8,400)
Write-Offs	(200)		(800)
Recoveries Collected	0		0
Ending Balance	33,100		33,100
Retail (Non-Hardship), Wholesale, and Other Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	94,500		81,500
Uncollectible Expense	10,500		31,100
Uncollectible Costs Deferred	20,400		41,500
Write-Offs	(11,800)		(49,300)
Recoveries Collected	2,700		9,300
Ending Balance	116,300		116,300
Retail (Non-Hardship), Wholesale, and Other Receivables | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	20,400		17,200
Uncollectible Expense	3,800		10,000
Uncollectible Costs Deferred	4,900		8,300
Write-Offs	(4,600)		(14,000)
Recoveries Collected	1,100		3,200
Ending Balance	25,600		25,600
Retail (Non-Hardship), Wholesale, and Other Receivables | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	34,100		31,500
Uncollectible Expense	4,500		11,300
Uncollectible Costs Deferred	10,400		17,300
Write-Offs	(6,300)		(20,500)
Recoveries Collected	1,000		3,800
Ending Balance	$ 43,700		43,700
Restatement Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			23,800
Restatement Adjustment | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			22,200
Restatement Adjustment | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			(1,300)
Restatement Adjustment | PSNH
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			300
Restatement Adjustment | Hardship Accounts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			21,600
Restatement Adjustment | Hardship Accounts | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			21,300
Restatement Adjustment | Hardship Accounts | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			(1,600)
Restatement Adjustment | Retail (Non-Hardship), Wholesale, and Other Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			2,200
Restatement Adjustment | Retail (Non-Hardship), Wholesale, and Other Receivables | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			900
Restatement Adjustment | Retail (Non-Hardship), Wholesale, and Other Receivables | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance			$ 300

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Components of Other Income, Net (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Summary of Accounting Policies [Line Items]
Other income, net	$ 29,218,000	$ 26,968,000	$ 83,565,000	$ 103,818,000
Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other income, net	11,000,000	10,100,000	34,300,000	23,200,000
AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	10,300,000	10,500,000	31,800,000	34,500,000
Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other income, net	3,900,000	6,100,000	13,800,000	37,000,000
Unrealized gain associated with investment		0	2,400,000	20,400,000
Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	1,000,000	(2,800,000)	(1,500,000)	(2,300,000)
Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	1,500,000	2,900,000	3,300,000	10,800,000
Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other income, net	1,500,000	0	1,800,000	200,000
Other
Summary of Accounting Policies [Line Items]
Other income, net	0	200,000	100,000	400,000
CL&P
Summary of Accounting Policies [Line Items]
Other income, net	5,917,000	4,831,000	16,273,000	11,564,000
CL&P | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other income, net	900,000	1,700,000	3,000,000	100,000
CL&P | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	3,500,000	3,600,000	11,400,000	9,400,000
CL&P | Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other income, net	0	0	0	200,000
CL&P | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	1,300,000	(800,000)	0	900,000
CL&P | Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	200,000	300,000	1,800,000	1,100,000
CL&P | Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other income, net	0	0	0	0
CL&P | Other
Summary of Accounting Policies [Line Items]
Other income, net	0	0	100,000	(100,000)
NSTAR Electric
Summary of Accounting Policies [Line Items]
Other income, net	12,802,000	10,735,000	38,152,000	32,479,000
NSTAR Electric | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other income, net	7,200,000	5,600,000	22,200,000	18,000,000
NSTAR Electric | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	5,500,000	5,600,000	15,800,000	14,700,000
NSTAR Electric | Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other income, net	100,000	200,000	400,000	600,000
NSTAR Electric | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	(200,000)	(900,000)	(1,500,000)	(1,500,000)
NSTAR Electric | Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	100,000	100,000	700,000	500,000
NSTAR Electric | Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other income, net	0	0	300,000	0
NSTAR Electric | Other
Summary of Accounting Policies [Line Items]
Other income, net	100,000	100,000	300,000	200,000
PSNH
Summary of Accounting Policies [Line Items]
Other income, net	4,065,000	4,634,000	10,882,000	14,640,000
PSNH | Pension, SERP and PBOP Non-Service Income Components
Summary of Accounting Policies [Line Items]
Other income, net	1,800,000	1,400,000	5,200,000	3,500,000
PSNH | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	900,000	1,000,000	3,500,000	2,100,000
PSNH | Equity in Earnings of Unconsolidated Affiliates
Summary of Accounting Policies [Line Items]
Other income, net	0	0	0	0
PSNH | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	200,000	(300,000)	100,000	0
PSNH | Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	1,200,000	2,500,000	2,000,000	9,000,000
PSNH | Gain on Sale of Property
Summary of Accounting Policies [Line Items]
Other income, net	0	0	0	0
PSNH | Other
Summary of Accounting Policies [Line Items]
Other income, net	$ 0	$ 0	$ 100,000	$ 0

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Gross Tax Receipts [Line Items]
Gross receipts taxes	$ 48.4	$ 42.6	$ 129.1	$ 124
CL&P
Schedule of Gross Tax Receipts [Line Items]
Gross receipts taxes	$ 45.6	$ 39.8	$ 114.2	$ 107.8

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Non-cash Investing Activities (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	$ 357.4	$ 317.8
CL&P
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	97.8	107.6
NSTAR Electric
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	92.6	79
PSNH
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	$ 50	$ 35.8

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Cash Balances to Cash and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	$ 729,993	$ 15,432
Cash, Cash Equivalents and Restricted Cash as reported on the Statements of Cash Flows	829,003	117,063	$ 151,880	$ 209,324
Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	51,300	52,500
Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	45,600	46,000
Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	2,100	3,200
CL&P
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	8,173	0
Cash, Cash Equivalents and Restricted Cash as reported on the Statements of Cash Flows	17,235	4,971	14,281	91,613
CL&P | Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	8,600	4,600
CL&P | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	400	400
CL&P | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
NSTAR Electric
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	87	52
Cash, Cash Equivalents and Restricted Cash as reported on the Statements of Cash Flows	12,409	6,312	6,508	14,659
NSTAR Electric | Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	12,200	6,200
NSTAR Electric | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	100	0
NSTAR Electric | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
PSNH
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents as reported on the Balance Sheets	767	413
Cash, Cash Equivalents and Restricted Cash as reported on the Statements of Cash Flows	22,595	36,688	$ 24,012	$ 52,723
PSNH | Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	19,100	32,500
PSNH | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	600	600
PSNH | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 2,100	$ 3,200

REGULATORY ACCOUNTING - Compone

REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 5,646,100	$ 5,514,700
Less: Current Portion	762,883	651,112
Total Long-Term Regulatory Assets	4,883,165	4,863,639
Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	2,256,100	2,382,900
Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	731,200	725,800
Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	532,900	565,300
Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	739,600	540,600
Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	531,800	411,500
Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	311,800	334,500
Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	318,900	331,500
Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	105,800	97,200
Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	118,000	125,400
CL&P
Regulatory Assets [Line Items]
Total Regulatory Assets	2,006,500	1,735,900
Less: Current Portion	273,792	178,607
Total Long-Term Regulatory Assets	1,732,739	1,557,261
CL&P | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	483,300	539,000
CL&P | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	459,800	458,800
CL&P | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
CL&P | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	510,700	274,600
CL&P | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	174,400	78,300
CL&P | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	311,800	329,200
CL&P | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
CL&P | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	32,300	30,800
CL&P | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	34,200	25,200
NSTAR Electric
Regulatory Assets [Line Items]
Total Regulatory Assets	1,472,700	1,535,600
Less: Current Portion	278,604	285,591
Total Long-Term Regulatory Assets	1,194,092	1,250,029
NSTAR Electric | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	601,400	629,800
NSTAR Electric | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	110,000	108,000
NSTAR Electric | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	171,400	200,600
NSTAR Electric | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	203,000	207,100
NSTAR Electric | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	273,800	284,600
NSTAR Electric | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	56,200	50,300
NSTAR Electric | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	56,900	55,200
PSNH
Regulatory Assets [Line Items]
Total Regulatory Assets	912,400	945,800
Less: Current Portion	103,570	84,053
Total Long-Term Regulatory Assets	808,784	861,672
PSNH | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	205,700	218,200
PSNH | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	13,700	12,800
PSNH | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	532,900	565,300
PSNH | Storm Restoration Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	57,500	65,400
PSNH | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	82,300	65,800
PSNH | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
PSNH | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
PSNH | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	3,800	3,600
PSNH | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 16,500	$ 14,700

REGULATORY ACCOUNTING - Narrati

REGULATORY ACCOUNTING - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Regulatory costs	$ 5,646.1	$ 5,514.7
Amount of regulatory costs not yet approved	183.9	146
CL&P
Regulatory Assets [Line Items]
Regulatory costs	2,006.5	1,735.9
Amount of regulatory costs not yet approved	84.2	51.8
PSNH
Regulatory Assets [Line Items]
Regulatory costs	912.4	945.8
Amount of regulatory costs not yet approved	15.3	18
NSTAR Electric
Regulatory Assets [Line Items]
Regulatory costs	1,472.7	1,535.6
Amount of regulatory costs not yet approved	55	55.7
COVID-19
Regulatory Assets [Line Items]
Deferred costs	15.1
Deferred costs related to uncollectible expense incurred at our natural gas distribution segment	11.4
Storm Restoration Costs
Regulatory Assets [Line Items]
Regulatory costs	739.6	540.6
Storm Restoration Costs | CL&P
Regulatory Assets [Line Items]
Regulatory costs	510.7	274.6
Storm Restoration Costs | PSNH
Regulatory Assets [Line Items]
Regulatory costs	57.5	65.4
Storm Restoration Costs | NSTAR Electric
Regulatory Assets [Line Items]
Regulatory costs	171.4	$ 200.6
Storm Restoration Costs | Tropical Storm Isaias
Regulatory Assets [Line Items]
Regulatory costs	276
Storm Restoration Costs | Tropical Storm Isaias | CL&P
Regulatory Assets [Line Items]
Regulatory costs	$ 257

REGULATORY ACCOUNTING - Compo_2

REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 4,176,200	$ 4,019,200
Less: Current Portion	464,673	361,152
Total Long-Term Regulatory Liabilities	3,711,488	3,658,042
EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	2,805,300	2,844,600
Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	610,400	559,800
Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	79,500	84,500
Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	445,700	325,100
AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	77,100	73,200
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	158,200	132,000
CL&P
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,361,200	1,247,800
Less: Current Portion	164,946	82,763
Total Long-Term Regulatory Liabilities	1,196,255	1,164,991
CL&P | EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,013,900	1,022,800
CL&P | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	93,000	64,600
CL&P | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
CL&P | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	171,100	94,800
CL&P | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	45,000	46,000
CL&P | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	38,200	19,600
NSTAR Electric
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,745,500	1,725,800
Less: Current Portion	210,744	209,180
Total Long-Term Regulatory Liabilities	1,534,760	1,516,585
NSTAR Electric | EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,050,100	1,071,200
NSTAR Electric | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	354,800	330,600
NSTAR Electric | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	68,700	72,200
NSTAR Electric | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	181,900	165,600
NSTAR Electric | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	32,100	27,200
NSTAR Electric | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	57,900	59,000
PSNH
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	467,700	479,200
Less: Current Portion	61,457	65,766
Total Long-Term Regulatory Liabilities	406,211	413,381
PSNH | EDIT due to Tax Cuts and Jobs Act
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	388,700	392,800
PSNH | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	12,900	16,300
PSNH | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
PSNH | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	56,200	57,000
PSNH | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
PSNH | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 9,900	$ 13,100

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Summary of Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 16,435,400	$ 15,880,000
Distribution - Natural Gas	4,073,000	3,931,100
Transmission - Electric	11,601,700	10,958,400
Distribution - Water	1,683,800	1,726,500
Solar	201,200	200,200
Utility	33,995,100	32,696,200
Other	1,193,000	1,025,600
Property, Plant and Equipment, Gross	35,188,100	33,721,800
Less: Accumulated Depreciation
Utility	(7,731,000)	(7,483,500)
Other	(455,200)	(387,400)
Total Accumulated Depreciation	(8,186,200)	(7,870,900)
Property, Plant and Equipment, Net	27,001,900	25,850,900
Construction Work in Progress	2,091,100	1,734,600
Total Property, Plant and Equipment, Net	29,092,981	27,585,470
CL&P
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	6,728,700	6,485,500
Transmission - Electric	5,299,000	5,043,000
Solar	0	0
Property, Plant and Equipment, Gross	12,027,700	11,528,500
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,453,100)	(2,385,700)
Property, Plant and Equipment, Net	9,574,600	9,142,800
Construction Work in Progress	490,700	483,000
Total Property, Plant and Equipment, Net	10,065,346	9,625,765
NSTAR Electric
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	7,414,000	7,163,700
Transmission - Electric	4,608,900	4,411,900
Solar	201,200	200,200
Property, Plant and Equipment, Gross	12,224,100	11,775,800
Less: Accumulated Depreciation
Total Accumulated Depreciation	(3,022,700)	(2,895,300)
Property, Plant and Equipment, Net	9,201,400	8,880,500
Construction Work in Progress	742,000	592,300
Total Property, Plant and Equipment, Net	9,943,408	9,472,770
PSNH
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	2,332,900	2,271,100
Transmission - Electric	1,689,000	1,498,700
Solar	0	0
Property, Plant and Equipment, Gross	4,021,900	3,769,800
Less: Accumulated Depreciation
Total Accumulated Depreciation	(832,800)	(799,900)
Property, Plant and Equipment, Net	3,189,100	2,969,900
Construction Work in Progress	130,400	159,600
Total Property, Plant and Equipment, Net	$ 3,319,483	$ 3,129,506

PROPERTY, PLANT AND EQUIPMENT_4

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Narrative (Details) - USD ($) $ in Thousands	Jul. 31, 2020	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Proceeds from the Sale of Hingham Water System			$ 110,536	$ 0
Disposed of by Sale | Hingham Water System
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 63,900
Goodwill	23,600
Proceeds from the Sale of Hingham Water System	$ 110,500
Pre-tax gain (loss) on sale of property, plant and equipment		$ 16,000
After-tax gain (loss) on the sale of property, plant and equipment		$ 3,500

DERIVATIVE INSTRUMENTS - Gross

DERIVATIVE INSTRUMENTS - Gross Fair Values and Net Amounts of Contracts (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current Derivative Assets | CL&P | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	$ 13.5	$ 12.2
Netting	(0.4)	(0.4)
Net Amount Recorded as a Derivative	13.1	11.8
Current Derivative Assets | Other | Level 2
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	3.4	0
Netting	(0.7)	0
Net Amount Recorded as a Derivative	2.7	0
Long-term Derivative Assets | CL&P | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	59.1	67.5
Netting	(1.9)	(2.1)
Net Amount Recorded as a Derivative	57.2	65.4
Current Derivative Liabilities | CL&P | Level 3
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(69.2)	(67.8)
Netting	0	0
Net Amount Recorded as a Derivative	(69.2)	(67.8)
Current Derivative Liabilities | Other | Level 2
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	0	(5.2)
Netting	0	0
Net Amount Recorded as a Derivative	0	(5.2)
Long-Term Derivative Liabilities | CL&P | Level 3
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(312.9)	(338.6)
Netting	0	0
Net Amount Recorded as a Derivative	(312.9)	(338.6)
Long-Term Derivative Liabilities | Other | Level 2
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	0	(0.1)
Netting	0	0
Net Amount Recorded as a Derivative	$ 0	$ (0.1)

DERIVATIVE INSTRUMENTS - Narrat

DERIVATIVE INSTRUMENTS - Narrative (Details) MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020USD ($)MW	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)MMBTUMWhMW	Sep. 30, 2019USD ($)	Dec. 31, 2019MMBTUMW
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	676		676		676
Amount of natural gas to be purchased under futures contracts | MMBTU			11.4		9.6
Gains (losses) on deferred as regulatory costs | $	$ (2.6)	$ (9.2)	$ (20.6)	$ (19.5)
Level 3 | Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts			1.00%
Level 3 | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts			12.00%
Level 3 | Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts			10.90%
CL&P
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 - Summar

DERIVATIVE INSTRUMENTS - Summary of Level 3 Derivative Contracts and Significant Unobservable Inputs Used (Details) - CL&P - Level 3 - $ / KWmo	Sep. 30, 2020	Dec. 31, 2019
Capacity Prices | Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	4.30	3.01
Capacity Prices | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	5.12	7.34
Capacity Prices | Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	4.57
Forward Reserve Prices | Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.54	0.80
Forward Reserve Prices | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.90	1.90
Forward Reserve Prices | Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.72

DERIVATIVE INSTRUMENTS - Change

DERIVATIVE INSTRUMENTS - Changes in the Level 3 Category of Derivative Assets Measured at Fair Value on a Recurring Basis (Details) - CL&P - Level 3 - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	$ (322)	$ (345.4)	$ (329.2)	$ (356.5)
Net Realized/Unrealized Losses Included in Regulatory Assets	(4.7)	(8.5)	(22.3)	(16.4)
Settlements	14.9	11.6	39.7	30.6
Fair Value as of End of Period	$ (311.8)	$ (342.3)	$ (311.8)	$ (342.3)

MARKETABLE SECURITIES - Narrati

MARKETABLE SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities	$ 36.8		$ 36.8		$ 45.7
Unrealized gain (loss) recorded in other income	1.6	$ 2.4	(1)	$ 5.7
CYAPC and YAEC
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities	189.5		189.5		182.8
Marketable securities held in nuclear decommissioning trust	$ 194		$ 194		$ 198.1

MARKETABLE SECURITIES - Summary

MARKETABLE SECURITIES - Summary of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Amortized Cost	$ 216.1	$ 228.4
Pre-Tax Unrealized Gains	11.1	5.8
Pre-Tax Unrealized Losses	(0.2)	(0.1)
Fair Value	$ 227	$ 234.1

MARKETABLE SECURITIES - Contrac

MARKETABLE SECURITIES - Contractual Maturities of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Amortized Cost
Less than one year	$ 51.1
One to five years	45.2
Six to ten years	43.9
Greater than ten years	75.9
Amortized Cost	216.1	$ 228.4
Fair Value
Less than one year	51.1
One to five years	47.4
Six to ten years	47
Greater than ten years	81.5
Fair Value	$ 227	$ 234.1

MARKETABLE SECURITIES - Marketa

MARKETABLE SECURITIES - Marketable Securities Recorded at Fair Value on a Recurring Basis by Level (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 453.3	$ 462.6
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	271.9	274.5
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	181.4	188.1
Mutual Funds and Equities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	226.3	228.5
Money Market Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	45.6	46
U.S. Government Issued Debt Securities (Agency and Treasury) | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	64.7	96.8
Corporate Debt Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	64.9	44
Asset-Backed Debt Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	12	12.9
Municipal Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	30.4	26.7
Other Fixed Income Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 9.4	$ 7.7

SHORT-TERM AND LONG-TERM DEBT -

SHORT-TERM AND LONG-TERM DEBT - Narrative (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Nov. 01, 2020	Oct. 21, 2020	Jul. 31, 2020	May 15, 2020	Jan. 27, 2020	Dec. 31, 2019
CL&P
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	$ 235,900,000						$ 63,800,000
PSNH
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	29,100,000						27,000,000
Amount of long-term debt approved for issuance				$ 200,000,000
NSTAR Electric
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	36,600,000						30,300,000
NSTAR Gas
Line of Credit Facility [Line Items]
Amount of long-term debt approved for issuance						$ 270,000,000
Commercial Paper | NSTAR Electric
Line of Credit Facility [Line Items]
Maximum borrowing capacity	650,000,000
Line of Credit
Line of Credit Facility [Line Items]
Amount outstanding under line of credit	0						0
Line of Credit | NSTAR Electric
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 650,000,000
Debt instrument term	5 years
Amount outstanding under line of credit	$ 0						$ 0
Eversource Parent | Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity	1,450,000,000
Eversource Parent | Commercial Paper | Subsequent Event
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 2,000,000,000
Eversource Parent | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,450,000,000
Debt instrument term	5 years
Line of Credit | CL&P
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 450,000,000
Amount outstanding under line of credit	$ 0
Line of Credit | PSNH
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 300,000,000
Revolving Credit Facility | Subsequent Event
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 550,000,000

SHORT-TERM AND LONG-TERM DEBT_2

SHORT-TERM AND LONG-TERM DEBT - Borrowings Outstanding and Available under the Commercial Paper Programs (Details) - Commercial Paper - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Borrowings outstanding	$ 0	$ 1,224.9
Available borrowing capacity	$ 1,450	$ 225.1
Weighted-average interest rate	0.00%	1.98%
NSTAR Electric
Debt Instrument [Line Items]
Borrowings outstanding	$ 60.5	$ 10.5
Available borrowing capacity	$ 589.5	$ 639.5
Weighted-average interest rate	0.10%	1.63%

SHORT-TERM AND LONG-TERM DEBT_3

SHORT-TERM AND LONG-TERM DEBT - Summary of Long-Term Debt Issuance and Repayments (Details) - USD ($) $ in Thousands	1 Months Ended						9 Months Ended
	Sep. 30, 2020	Aug. 31, 2020	May 31, 2020	Apr. 30, 2020	Mar. 31, 2020	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Repayments							$ (302,236)	$ (250,855)
Senior Notes | Eversource Parent 3.45% Series P Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Issuances		$ 300,000				$ 350,000
Interest rate, stated percentage		3.45%				3.45%
Aggregate outstanding principal amount	$ 650,000						650,000
Senior Notes | Eversource Parent 0.80% Series Q Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Issuances		$ 300,000
Interest rate, stated percentage		0.80%
Senior Notes | Eversource Parent 1.65% Series R Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Issuances		$ 600,000
Interest rate, stated percentage		1.65%
NSTAR Electric
Debt Instrument [Line Items]
Repayments							$ (95,000)	$ 0
NSTAR Electric | Senior Notes | 3.95% 2020 Debentures
Debt Instrument [Line Items]
Issuances					$ 400,000
Interest rate, stated percentage					3.95%
NSTAR Electric | Senior Notes | 5.10% Series E Senior Notes
Debt Instrument [Line Items]
Repayments					$ (95,000)
Interest rate, stated percentage					5.10%
PSNH | Senior Notes | 2.40% Series U First Mortgage Bonds
Debt Instrument [Line Items]
Issuances		$ 150,000
Interest rate, stated percentage		2.40%
NSTAR Gas | Senior Notes | NSTAR Gas 4.46% Series N First Mortgage Bonds
Debt Instrument [Line Items]
Repayments						$ (125,000)
Interest rate, stated percentage						4.46%
NSTAR Gas | Senior Notes | NSTAR Gas 2.33% Series R First Mortgage Bonds
Debt Instrument [Line Items]
Issuances			$ 75,000
Interest rate, stated percentage			2.33%
NSTAR Gas | Senior Notes | NSTAR Gas 3.15% Series S First Mortgage Bonds
Debt Instrument [Line Items]
Issuances			$ 115,000
Interest rate, stated percentage			3.15%
Yankee Gas | Senior Notes | Yankee Gas 4.87% Series K First Mortgage Bonds
Debt Instrument [Line Items]
Repayments				$ (50,000)
Interest rate, stated percentage				4.87%
Yankee Gas | Senior Notes | Yankee Gas 2.90% Series R First Mortgage Bonds
Debt Instrument [Line Items]
Issuances	$ 70,000
Interest rate, stated percentage	2.90%						2.90%
Aquarion | Term Loans and Mortgage Bonds | Aquarion Water Company of Massachusetts, Inc. and Aquarion Water Capital of Massachusetts, Inc. various term loans and general mortgage bonds
Debt Instrument [Line Items]
Repayments	$ (32,200)

RATE REDUCTION BONDS AND VARI_3

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Narrative (Details) - PSNH - Rate Reduction Bonds	May 08, 2018USD ($)
Debt Instrument [Line Items]
Amount of securitized rate reduction bonds issued	$ 635,700,000
Weighted average interest rate	3.66%

RATE REDUCTION BONDS AND VARI_4

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 5,646,100	$ 5,514,700
Regulatory Liabilities	3,711,488	3,658,042
Accrued Interest (included in Other Current Liabilities)	765,443	836,834
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	496,912	540,122
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	532,900	565,300
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	118,000	125,400
Special Deposits
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	51,300	52,500
Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	2,100	3,200
PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	912,400	945,800
Regulatory Liabilities	406,211	413,381
Accrued Interest (included in Other Current Liabilities)	36,182	32,736
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	496,912	540,122
PSNH | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Rate Reduction Bonds - Current Portion	43,200	43,200
Rate Reduction Bonds - Long-Term Portion	496,900	540,100
PSNH | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	532,900	565,300
PSNH | Securitized Stranded Costs | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	532,900	565,300
PSNH | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	16,500	14,700
PSNH | Other Regulatory Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory Liabilities	7,200	5,600
Accrued Interest (included in Other Current Liabilities)	3,200	8,600
PSNH | Special Deposits
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	19,100	32,500
PSNH | Special Deposits | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	18,800	32,500
PSNH | Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	2,100	3,200
PSNH | Other Long-Term Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	$ 2,100	$ 3,200

RATE REDUCTION BONDS AND VARI_5

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Income Statements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 134,066	$ 135,216	$ 403,067	$ 399,654
PSNH
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net)	7,360	20,421	39,034	39,944
Interest Expense on RRB Principal (included in Interest Expense)	14,942	16,378	44,029	44,654
PSNH | VIE | Rate Reduction Bonds
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net)	10,800	10,800	32,400	32,200
Interest Expense on RRB Principal (included in Interest Expense)	$ 4,900	$ 5,200	$ 14,900	$ 15,900

PENSION BENEFITS AND POSTRETI_3

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION - Components of Net Periodic Benefit Expense/(Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 18.7	$ 16.2	$ 57	$ 51.6
Interest Cost	44.4	54.8	133	163.8
Expected Return on Plan Assets	(99.2)	(91.6)	(298.8)	(275.4)
Actuarial Loss	50.7	35.6	150.7	107.9
Prior Service Cost/(Credit)	0.2	0.3	0.8	0.9
Total Net Periodic Benefit Expense/(Income)	14.8	15.3	42.7	48.8
PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.4	2	7.3	5.9
Interest Cost	6.1	8.1	18.3	24.5
Expected Return on Plan Assets	(18.3)	(16.7)	(55.1)	(50.1)
Actuarial Loss	2.2	2.1	6.3	6.2
Prior Service Cost/(Credit)	(5.3)	(5.8)	(15.9)	(17.6)
Total Net Periodic Benefit Expense/(Income)	(12.9)	(10.3)	(39.1)	(31.1)
CL&P | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	5.4	4.4	16.5	13.6
Interest Cost	9.3	11.4	28.1	34.4
Expected Return on Plan Assets	(19.8)	(18.1)	(59.6)	(55.1)
Actuarial Loss	9.7	6.3	29.4	20.6
Prior Service Cost/(Credit)	0	0	0	0
Total Net Periodic Benefit Expense/(Income)	4.6	4	14.4	13.5
Intercompany Allocations	2.4	2	6.7	6.5
CL&P | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.4	0.3	1.3	1.1
Interest Cost	1.1	1.6	3.3	4.7
Expected Return on Plan Assets	(2.5)	(2.2)	(7.4)	(6.9)
Actuarial Loss	0.3	0.3	0.9	1
Prior Service Cost/(Credit)	0.3	0.2	0.8	0.8
Total Net Periodic Benefit Expense/(Income)	(0.4)	0.2	(1.1)	0.7
Intercompany Allocations	(0.3)	(0.2)	(0.9)	(0.6)
NSTAR Electric | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	3.8	3.6	11.4	11
Interest Cost	9.7	12.3	29	36.6
Expected Return on Plan Assets	(25.7)	(24.2)	(77.2)	(72.9)
Actuarial Loss	14	11.8	41.3	33.1
Prior Service Cost/(Credit)	0	0	0.2	0.2
Total Net Periodic Benefit Expense/(Income)	1.8	3.5	4.7	8
Intercompany Allocations	2.3	1.9	6.5	6.1
NSTAR Electric | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.5	0.4	1.6	1.3
Interest Cost	1.7	2.4	5	7.1
Expected Return on Plan Assets	(8.5)	(7.5)	(25.5)	(22.6)
Actuarial Loss	0.6	0.8	1.8	2.5
Prior Service Cost/(Credit)	(4.2)	(4.2)	(12.7)	(12.7)
Total Net Periodic Benefit Expense/(Income)	(9.9)	(8.1)	(29.8)	(24.4)
Intercompany Allocations	(0.4)	(0.3)	(1)	(0.9)
PSNH | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2	1.5	6.2	5.6
Interest Cost	4.8	6	14.5	18.2
Expected Return on Plan Assets	(11.1)	(10.1)	(33.5)	(30.6)
Actuarial Loss	3.8	2.3	11.8	8.2
Prior Service Cost/(Credit)	0	0	0	0
Total Net Periodic Benefit Expense/(Income)	(0.5)	(0.3)	(1)	1.4
Intercompany Allocations	0.8	0.5	2.2	1.8
PSNH | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.2	0.2	0.6	0.5
Interest Cost	0.7	0.8	2.1	2.5
Expected Return on Plan Assets	(1.4)	(1.3)	(4.2)	(4)
Actuarial Loss	0.2	0.1	0.6	0.3
Prior Service Cost/(Credit)	0.1	0.1	0.3	0.3
Total Net Periodic Benefit Expense/(Income)	(0.2)	(0.1)	(0.6)	(0.4)
Intercompany Allocations	$ (0.1)	$ (0.1)	$ (0.4)	$ (0.3)

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Environmental Sites and Related Reserves (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)site	Dec. 31, 2019USD ($)site
Site Contingency [Line Items]
Number of Sites | site	55	57
Reserve | $	$ 78.8	$ 81
CL&P
Site Contingency [Line Items]
Number of Sites | site	15	15
Reserve | $	$ 11.6	$ 11.4
NSTAR Electric
Site Contingency [Line Items]
Number of Sites | site	13	15
Reserve | $	$ 4.6	$ 8
PSNH
Site Contingency [Line Items]
Number of Sites | site	9	9
Reserve | $	$ 7.2	$ 7.5

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Environmental Matters (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Site Contingency [Line Items]
Reserve balance	$ 78.8	$ 81
MGP Sites
Site Contingency [Line Items]
Reserve balance	$ 69.5	$ 67.9

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Non-Cancellable Commitments under Purchase Commitment Contracts (Details) - Renewable Energy - NSTAR Electric $ in Millions	Sep. 30, 2020USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
Remainder of 2020	$ 24.3
2021	98.5
2022	100
2023	75.4
2024	72.9
Thereafter	594.5
Total	$ 965.6

COMMITMENTS AND CONTINGENCIES_4

COMMITMENTS AND CONTINGENCIES - Guarantees and Indemnifications (Details) - USD ($)	Sep. 30, 2020	Sep. 16, 2020	Oct. 25, 2019
Sunrise Wind, LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)			$ 15,400,000
Ownership interest			50.00%
Surety Bond
Guarantor Obligations [Line Items]
Maximum exposure (up to)	$ 30,900,000
Lease Payments for Real Estate
Guarantor Obligations [Line Items]
Maximum exposure (up to)	5,600,000
Real Estate Purchase
Guarantor Obligations [Line Items]
Maximum exposure (up to)	2,500,000
Sunrise Wind, LLC - Offshore Wind
Guarantor Obligations [Line Items]
Maximum exposure (up to)	$ 2,200,000
Letter of Credit Guarantee | Eversource Investment, LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)		$ 25,000,000

COMMITMENTS AND CONTINGENCIES_5

COMMITMENTS AND CONTINGENCIES - Spent Nuclear Fuel Obligations - Yankee Companies (Details) - USD ($) $ in Millions	Jun. 12, 2019	Feb. 21, 2019	May 22, 2017	Dec. 31, 2019	Jul. 31, 2019
Loss Contingencies [Line Items]
Damages awarded	$ 0.5
Remaining damages sought		$ 1
Damages paid					$ 0.5
DOE settlement payment				$ 29
YAEC
Loss Contingencies [Line Items]
Damages awarded				2.8
Total amount of damages awarded				5.4
MYAPC
Loss Contingencies [Line Items]
Damages awarded				5
Total amount of damages awarded				$ 21
CYAPC, YAEC, and MYAPC
Loss Contingencies [Line Items]
Damages sought			$ 104.4
Damages awarded		103.2
CYAPC
Loss Contingencies [Line Items]
Damages awarded		40.7
YAEC
Loss Contingencies [Line Items]
Damages awarded		28.1
MYAPC
Loss Contingencies [Line Items]
Damages awarded		$ 34.4

COMMITMENTS AND CONTINGENCIES_6

COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) - USD ($) $ in Millions	Apr. 29, 2016	Oct. 16, 2014	Sep. 30, 2020	Oct. 15, 2014	Dec. 31, 2019
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 First, Second and Third Complaints | Minimum
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project				11.14%
FERC ROE First, Second and Third Complaints | Maximum
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project				13.10%
FERC ROE Complaints
Loss Contingencies [Line Items]
Period of complaint			15 months
Basis point change			0.10%
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%
FERC ROE First Complaint
Loss Contingencies [Line Items]
Base ROE subsequently authorized		10.57%
Percentage of maximum ROE for any incentive project		11.74%
Amounts associated with first complaint refunded			38.9
FERC ROE First Complaint | CL&P
Loss Contingencies [Line Items]
Amounts associated with first complaint refunded			22.4
FERC ROE First Complaint | NSTAR Electric
Loss Contingencies [Line Items]
Amounts associated with first complaint refunded			13.7
FERC ROE First Complaint | PSNH
Loss Contingencies [Line Items]
Amounts associated with first complaint refunded			$ 2.8
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		$ 39.1
FERC ROE Second Complaint | CL&P
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			21.4		21.4
FERC ROE Second Complaint | NSTAR Electric
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			14.6		14.6
FERC ROE Second Complaint | PSNH
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			$ 3.1		$ 3.1

COMMITMENTS AND CONTINGENCIES_7

COMMITMENTS AND CONTINGENCIES - Eversource and NSTAR Electric Boston Harbor Civil Action (Details)	Jul. 15, 2016kV
Commitments and Contingencies Disclosure [Abstract]
Amount of capacity required for installation of distribution cable (in kV)	115

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
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	496,912	540,122
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	15,814,500	14,098,200
Rate Reduction Bonds	540,100	583,300
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	166,600	162,000
Long-Term Debt	17,943,700	15,170,200
Rate Reduction Bonds	603,000	625,900
CL&P
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
CL&P | 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	3,518,100	3,518,100
Rate Reduction Bonds	0	0
CL&P | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	122,000	117,800
Long-Term Debt	4,336,700	4,058,000
Rate Reduction Bonds	0	0
NSTAR Electric
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 | 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	3,642,800	3,342,100
Rate Reduction Bonds	0	0
NSTAR Electric | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	44,600	44,200
Long-Term Debt	4,285,400	3,659,900
Rate Reduction Bonds	0	0
PSNH
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Rate Reduction Bonds	496,912	540,122
PSNH | 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	1,099,000	951,600
Rate Reduction Bonds	540,100	583,300
PSNH | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	1,192,100	1,005,700
Rate Reduction Bonds	$ 603,000	$ 625,900

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent [Roll Forward]
OCI Before Reclassifications							$ (1,300)	$ 3,900
Amounts Reclassified from AOCI							6,000	4,100
Other Comprehensive Income (Loss), Net of Tax	$ 2,161	$ 553	$ 1,948	$ 1,624	$ 4,163	$ 2,196	4,662	7,983
Total
AOCI Attributable to Parent [Roll Forward]
Balance			(65,100)			(60,000)	(65,100)	(60,000)
Other Comprehensive Income (Loss), Net of Tax	2,161	$ 553	1,948	1,624	$ 4,163	2,196
Balance	(60,400)			(52,000)			(60,400)	(52,000)
Qualified Cash Flow Hedging Instruments
AOCI Attributable to Parent [Roll Forward]
Balance			(3,000)			(4,400)	(3,000)	(4,400)
OCI Before Reclassifications							0	0
Amounts Reclassified from AOCI							1,200	900
Other Comprehensive Income (Loss), Net of Tax							1,200	900
Balance	(1,800)			(3,500)			(1,800)	(3,500)
Unrealized Gains on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Balance			700			(500)	700	(500)
OCI Before Reclassifications							300	1,300
Amounts Reclassified from AOCI							0	0
Other Comprehensive Income (Loss), Net of Tax							300	1,300
Balance	1,000			800			1,000	800
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Balance			$ (62,800)			$ (55,100)	(62,800)	(55,100)
OCI Before Reclassifications							(1,600)	2,600
Amounts Reclassified from AOCI							4,800	3,200
Other Comprehensive Income (Loss), Net of Tax							3,200	5,800
Balance	$ (59,600)			$ (49,300)			$ (59,600)	$ (49,300)

COMMON SHARES - Common Shares A

COMMON SHARES - Common Shares Authorized and Issued (Details) - $ / shares	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Par value (in dollars per share)	$ 5	$ 5	$ 5
Authorized (in shares)	380,000,000			380,000,000
Issued (in shares)	357,818,402			345,858,402
CL&P
Class of Stock [Line Items]
Par value (in dollars per share)	$ 10
Authorized (in shares)	24,500,000			24,500,000
Issued (in shares)	6,035,205			6,035,205
NSTAR Electric
Class of Stock [Line Items]
Par value (in dollars per share)	$ 1
Authorized (in shares)	100,000,000			100,000,000
Issued (in shares)	200			200
PSNH
Class of Stock [Line Items]
Par value (in dollars per share)	$ 1
Authorized (in shares)	100,000,000			100,000,000
Issued (in shares)	301			301

COMMON SHARES - Narrative (Deta

COMMON SHARES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 15, 2020	Mar. 26, 2020	Mar. 23, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Equity [Abstract]
Equity offering (in shares)	6,000,000			5,960,000	6,000,000	5,980,000
Price per share (in dollars per share)	$ 86.26
Net proceeds from common shares issued directly by the Company	$ 509,200	$ 314,100	$ 105,700				$ 929,000	$ 929,025	$ 426,902
Common shares issuable pursuant to forward sale agreement (in shares)		4,460,000	1,500,000			11,960,000
Forward sale price (in dollars per share)		$ 71.48
Treasury stock (in shares)					15,977,757			15,020,929
Common stock outstanding (in shares)					329,880,645			342,797,473

COMMON SHAREHOLDERS' EQUITY A_2

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Equity [Abstract]
Dividends on preferred stock	$ 1,880	$ 1,880	$ 1,880	$ 1,880	$ 1,880	$ 1,880	$ 5,600	$ 5,600
Noncontrolling interest attributed to preferred stock of subsidiaries	$ 155,570						$ 155,570		$ 155,570

EARNINGS PER SHARE - Narrative

EARNINGS PER SHARE - Narrative (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Antidilutive share awards excluded from the EPS computation (in shares)	0	0	52,747	0

EARNINGS PER SHARE - Components

EARNINGS PER SHARE - Components of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 346,260	$ 318,884	$ 933,244	$ 659,016
Weighted Average Common Shares Outstanding:
Basic (in shares)	343,076,614	324,037,169	337,375,172	320,442,253
Dilutive Effect of:
Share-Based Compensation Awards and Other (in shares)	696,988	737,972	686,403	691,636
Equity Forward Sale Agreement (in shares)	0	1,233,201	362,525	437,037
Dilutive Effect (in shares)	696,988	1,971,173	1,048,928	1,128,673
Diluted (in shares)	343,773,602	326,008,342	338,424,100	321,570,926
Basic EPS (in dollars per share)	$ 1.01	$ 0.98	$ 2.77	$ 2.06
Diluted EPS (in dollars per share)	$ 1.01	$ 0.98	$ 2.76	$ 2.05

REVENUES (Details)

REVENUES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 2,352,100	$ 2,168,400	$ 6,593,800	$ 6,434,100
Alternative Revenue Programs	(9,600)	(200)	69,800	24,500
Other Revenues	1,100	7,600	6,900	17,500
Operating Revenues	2,343,642	2,175,797	6,670,497	6,476,084
Lease revenue	$ 1,100	$ 1,200	$ 3,200	$ 3,400
Operating Lease, Income, Comprehensive Income [Extensible List]	us-gaap:Revenues	us-gaap:Revenues	us-gaap:Revenues	us-gaap:Revenues
Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 1,275,200	$ 1,124,400	$ 3,576,500	$ 3,382,300
Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	739,500	794,600	2,103,200	2,301,600
Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	106,200	106,800	308,900	321,300
Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,120,900	2,025,800	5,988,600	6,005,200
Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	111,600	80,200	252,100	203,900
Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	89,400	39,900	265,900	168,700
Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	28,500	17,300	81,500	55,200
Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,700	5,200	5,700	1,100
Other
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	322,300	258,100	900,700	767,100
Alternative Revenue Programs	0	0	0	0
Other Revenues	0	0	0	0
Operating Revenues	322,300	258,100	900,700	767,100
Other | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	19,000	15,400	55,600	43,700
Other | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	303,300	242,700	845,100	723,400
Other | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(669,600)	(548,300)	(1,833,200)	(1,548,700)
Alternative Revenue Programs	67,000	19,000	48,900	(50,800)
Other Revenues	0	0	0	0
Operating Revenues	(602,600)	(529,300)	(1,784,300)	(1,599,500)
Eliminations | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(1,400)	(1,400)	(3,700)	(3,400)
Eliminations | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(3,600)	(3,200)	(10,100)	(8,700)
Eliminations | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(5,000)	(4,600)	(13,800)	(12,100)
Eliminations | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(365,600)	(300,700)	(981,400)	(811,400)
Eliminations | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(299,000)	(243,000)	(838,000)	(725,200)
Eliminations | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,057,900	1,918,500	5,422,200	5,298,000
Alternative Revenue Programs	1,700	6,700	54,800	15,000
Other Revenues	700	6,400	4,900	14,200
Operating Revenues	2,060,300	1,931,600	5,481,900	5,327,200
Electric Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,183,900	1,041,400	3,063,700	2,879,800
Electric Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	682,700	736,600	1,815,700	2,002,000
Electric Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	91,000	90,600	248,400	254,000
Electric Distribution | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,957,600	1,868,600	5,127,800	5,135,800
Electric Distribution | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Distribution | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	79,600	33,100	231,100	123,900
Electric Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	18,400	12,300	56,400	40,000
Electric Distribution | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,300	4,500	6,900	(1,700)
Natural Gas Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	114,100	110,200	746,100	777,600
Alternative Revenue Programs	(4,000)	(7,600)	22,900	0
Other Revenues	100	800	1,000	2,300
Operating Revenues	110,200	103,400	770,000	779,900
Natural Gas Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	45,500	43,000	399,600	402,000
Natural Gas Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	41,100	41,600	243,500	254,900
Natural Gas Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	17,500	18,100	67,000	72,500
Natural Gas Distribution | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	104,100	102,700	710,100	729,400
Natural Gas Distribution | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Natural Gas Distribution | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	8,700	5,500	31,900	41,600
Natural Gas Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	800	500	2,500	1,900
Natural Gas Distribution | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	500	1,500	1,600	4,700
Electric Transmission | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	461,400	368,600	1,187,800	981,500
Alternative Revenue Programs	(72,300)	(20,900)	(52,700)	56,100
Other Revenues	200	100	500	300
Operating Revenues	389,300	347,800	1,135,600	1,037,900
Electric Transmission | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	458,200	365,500	1,177,900	971,600
Electric Transmission | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	3,200	3,100	9,900	9,900
Electric Transmission | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Water Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	66,000	61,300	170,200	158,600
Alternative Revenue Programs	(2,000)	2,600	(4,100)	4,200
Other Revenues	100	300	500	700
Operating Revenues	64,100	64,200	166,600	163,500
Water Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	45,800	40,000	113,200	100,500
Water Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	17,100	17,800	47,700	48,100
Water Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,300	1,300	3,600	3,500
Water Distribution | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	64,200	59,100	164,500	152,100
Water Distribution | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Water Distribution | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,100	1,300	2,900	3,200
Water Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,800	1,700	5,600	5,200
Water Distribution | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(1,100)	(800)	(2,800)	(1,900)
CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues	994,270	853,943	2,711,394	2,444,034
Lease revenue	200	300	600	700
CL&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,192,800	996,000	3,109,100	2,753,600
Alternative Revenue Programs	(65,000)	(15,200)	(27,800)	45,600
Other Revenues	200	4,100	2,000	7,900
CL&P | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	608,700	513,600	1,567,900	1,426,900
CL&P | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	244,700	247,000	670,400	708,400
CL&P | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	38,000	37,400	105,300	105,800
CL&P | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	891,400	798,000	2,343,600	2,241,100
CL&P | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	233,300	175,200	576,500	445,900
CL&P | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	60,000	13,800	163,900	39,600
CL&P | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	8,100	9,000	25,100	27,000
CL&P | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
CL&P | Eliminations
Disaggregation of Revenue [Line Items]
Operating Revenues	(133,700)	(131,000)	(371,900)	(363,100)
NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	875,371	878,669	2,270,174	2,358,174
Lease revenue	700	700	2,100	2,000
NSTAR Electric | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	980,000	963,300	2,563,800	2,628,400
Alternative Revenue Programs	8,200	9,800	31,100	19,100
Other Revenues	700	1,800	2,800	5,200
NSTAR Electric | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	415,400	374,400	1,057,900	1,027,800
NSTAR Electric | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	358,300	406,100	921,300	1,058,300
NSTAR Electric | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	30,600	32,400	82,100	90,100
NSTAR Electric | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	804,300	812,900	2,061,300	2,176,200
NSTAR Electric | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	153,100	132,900	430,300	383,100
NSTAR Electric | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	12,100	14,400	39,800	55,900
NSTAR Electric | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	10,500	3,100	32,400	13,200
NSTAR Electric | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
NSTAR Electric | Eliminations
Disaggregation of Revenue [Line Items]
Operating Revenues	(113,500)	(96,200)	(327,500)	(294,500)
PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues	283,669	280,431	815,261	797,766
PSNH | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	347,600	329,100	940,500	901,100
Alternative Revenue Programs	(13,800)	(8,800)	(1,200)	6,400
Other Revenues	0	600	600	1,400
PSNH | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	159,800	153,400	437,900	425,100
PSNH | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	80,100	84,100	225,300	236,800
PSNH | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	22,400	20,800	61,000	58,100
PSNH | Operating Segments | Total Retail Tariff Sale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	262,300	258,300	724,200	720,000
PSNH | Operating Segments | Transmission Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	71,800	57,400	171,100	142,600
PSNH | Operating Segments | Wholesale Revenue
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	7,500	4,900	27,400	28,400
PSNH | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	3,700	4,000	10,900	11,800
PSNH | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,300	4,500	6,900	(1,700)
PSNH | Eliminations
Disaggregation of Revenue [Line Items]
Operating Revenues	$ (50,100)	$ (40,500)	$ (124,600)	$ (111,100)

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)segment
CL&P
Segment Reporting Information [Line Items]
Number of reportable segments	1
NSTAR Electric
Segment Reporting Information [Line Items]
Number of reportable segments	1
PSNH
Segment Reporting Information [Line Items]
Number of reportable segments	1
Affiliated Entity
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased | $	$ 62.5

SEGMENT INFORMATION - Summary o

SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,343,642	$ 2,175,797	$ 6,670,497	$ 6,476,084
Depreciation and Amortization	(302,000)	(296,500)	(851,900)	(840,500)
Impairment of Northern Pass Transmission	0	0	0	(239,644)
Other Operating Expenses	(1,480,400)	(1,370,100)	(4,284,600)	(4,241,100)
Operating Income/(Loss)	561,230	509,238	1,534,006	1,154,926
Interest Expense	(134,066)	(135,216)	(403,067)	(399,654)
Other Income, Net	29,218	26,968	83,565	103,818
Net Income/(Loss) Attributable to Common Shareholders	346,260	318,884	933,244	659,016
Cash Flows Used for Investments in Plant			2,101,564	2,129,037
Assets	43,507,345		43,507,345		$ 41,123,915
Other
Segment Reporting Information [Line Items]
Operating Revenues	322,300	258,100	900,700	767,100
Depreciation and Amortization	(24,100)	(17,200)	(68,100)	(45,600)
Impairment of Northern Pass Transmission				0
Other Operating Expenses	(271,500)	(275,900)	(771,400)	(719,800)
Operating Income/(Loss)	26,700	(35,000)	61,200	1,700
Interest Expense	(38,700)	(41,700)	(119,000)	(130,300)
Other Income, Net	387,000	497,000	1,161,700	813,700
Net Income/(Loss) Attributable to Common Shareholders	381,200	435,200	1,108,900	697,200
Cash Flows Used for Investments in Plant			181,200	173,600
Assets	22,230,100		22,230,100		20,469,600
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(602,600)	(529,300)	(1,784,300)	(1,599,500)
Depreciation and Amortization	300	600	1,200	1,700
Impairment of Northern Pass Transmission				0
Other Operating Expenses	603,100	638,400	1,787,900	1,708,200
Operating Income/(Loss)	800	109,700	4,800	110,400
Interest Expense	7,100	13,900	27,600	40,000
Other Income, Net	(383,000)	(545,100)	(1,149,900)	(833,600)
Net Income/(Loss) Attributable to Common Shareholders	(375,100)	(421,500)	(1,117,500)	(683,200)
Cash Flows Used for Investments in Plant			0	0
Assets	(20,969,100)		(20,969,100)		(19,488,800)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	2,060,300	1,931,600	5,481,900	5,327,200
Depreciation and Amortization	(182,000)	(188,400)	(490,000)	(517,600)
Impairment of Northern Pass Transmission				0
Other Operating Expenses	(1,577,000)	(1,448,200)	(4,309,900)	(4,166,800)
Operating Income/(Loss)	301,300	295,000	682,000	642,800
Interest Expense	(53,300)	(53,200)	(160,700)	(153,300)
Other Income, Net	16,000	13,900	44,900	44,200
Net Income/(Loss) Attributable to Common Shareholders	205,500	197,300	450,600	422,700
Cash Flows Used for Investments in Plant			781,200	861,000
Assets	23,864,700		23,864,700		22,541,900
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	110,200	103,400	770,000	779,900
Depreciation and Amortization	(14,800)	(16,100)	(55,100)	(56,000)
Impairment of Northern Pass Transmission				0
Other Operating Expenses	(104,200)	(99,300)	(592,000)	(620,400)
Operating Income/(Loss)	(8,800)	(12,000)	122,900	103,500
Interest Expense	(10,100)	(11,700)	(32,100)	(35,400)
Other Income, Net	700	0	2,500	1,100
Net Income/(Loss) Attributable to Common Shareholders	(14,000)	(17,100)	73,800	57,600
Cash Flows Used for Investments in Plant			322,800	327,800
Assets	4,579,900		4,579,900		4,345,500
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	389,300	347,800	1,135,600	1,037,900
Depreciation and Amortization	(70,600)	(64,300)	(206,800)	(188,000)
Impairment of Northern Pass Transmission				(239,600)
Other Operating Expenses	(120,600)	(159,600)	(338,500)	(366,900)
Operating Income/(Loss)	198,100	123,900	590,300	243,400
Interest Expense	(31,100)	(33,600)	(93,800)	(94,500)
Other Income, Net	6,900	61,400	22,700	78,200
Net Income/(Loss) Attributable to Common Shareholders	125,600	107,500	381,800	138,400
Cash Flows Used for Investments in Plant			732,400	686,700
Assets	11,469,700		11,469,700		10,904,000
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	64,100	64,200	166,600	163,500
Depreciation and Amortization	(10,800)	(11,100)	(33,100)	(35,000)
Impairment of Northern Pass Transmission				0
Other Operating Expenses	(10,200)	(25,500)	(60,700)	(75,400)
Operating Income/(Loss)	43,100	27,600	72,800	53,100
Interest Expense	(8,000)	(8,900)	(25,100)	(26,200)
Other Income, Net	1,600	(200)	1,700	200
Net Income/(Loss) Attributable to Common Shareholders	23,100	$ 17,500	35,600	26,300
Cash Flows Used for Investments in Plant			84,000	$ 79,900
Assets	$ 2,332,000		$ 2,332,000		$ 2,351,700

ACQUISITION OF ASSETS OF COLU_2

ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS (Details) - Subsequent Event mile in Thousands, customer in Thousands, $ in Billions	Oct. 09, 2020USD ($)customercommunitymile
Business Acquisition [Line Items]
Number of customers	300
CMA
Business Acquisition [Line Items]
Cash purchase price | $	$ 1.1
CMA
Business Acquisition [Line Items]
Number of customers	330
Length of natural gas pipeline | mile	5
Number of communities served | community	60