Eversource Energy (ES) 10-Q 5 May 17 2017 Q1 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - shares	3 Months Ended
	Mar. 31, 2017	Apr. 30, 2017
Document And Entity [Line Items]
Entity Registrant Name	Eversource Energy
Entity Central Index Key	72,741
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Trading Symbol	ES
Entity Common Stock, Shares Outstanding (in shares)		316,885,808
The Connecticut Light And Power Company [Member]
Document And Entity [Line Items]
Entity Registrant Name	The Connecticut Light and Power Company
Entity Central Index Key	23,426
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		6,035,205
Public Service Company Of New Hampshire [Member]
Document And Entity [Line Items]
Entity Registrant Name	Public Service Company of New Hampshire
Entity Central Index Key	315,256
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		301
Western Massachusetts Electric Company [Member]
Document And Entity [Line Items]
Entity Registrant Name	Western Massachusetts Electric Company
Entity Central Index Key	106,170
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		434,653
NSTAR Electric Company [Member]
Document And Entity [Line Items]
Entity Registrant Name	NSTAR Electric Company
Entity Central Index Key	13,372
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		100

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and Cash Equivalents	$ 45,763	$ 30,251
Receivables, Net	879,451	847,301
Unbilled Revenues	166,710	168,490
Fuel, Materials, Supplies and Inventory	361,779	328,721
Regulatory Assets	875,037	887,625
Prepayments and Other Current Assets	182,659	215,284
Total Current Assets	2,511,399	2,477,672
Property, Plant and Equipment, Net	21,641,898	21,350,510
Deferred Debits and Other Assets:
Regulatory Assets	3,564,700	3,638,688
Goodwill	3,519,401	3,519,401
Marketable Securities	561,585	544,642
Other Long-Term Assets	556,193	522,260
Total Deferred Debits and Other Assets	8,201,879	8,224,991
Total Assets	32,355,176	32,053,173
Current Liabilities:
Notes Payable	975,500	1,148,500
Long-Term Debt – Current Portion	773,883	773,883
Accounts Payable	745,856	884,521
Regulatory Liabilities	199,160	146,787
Other Current Liabilities	639,366	684,914
Total Current Liabilities	3,333,765	3,638,605
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	5,758,603	5,607,207
Regulatory Liabilities	692,989	702,255
Derivative Liabilities	415,795	413,676
Accrued Pension and SERP	1,077,593	1,141,514
Other Long-Term Liabilities	848,776	853,260
Total Deferred Credits and Other Liabilities	8,793,756	8,717,912
Capitalization:
Long-Term Debt	9,267,891	8,829,354
Noncontrolling Interest - Preferred Stock of Subsidiaries	155,568	155,568
Common Shareholders' Equity:
Common Shares	1,669,392	1,669,392
Capital Surplus, Paid In	6,230,608	6,250,224
Retained Earnings	3,284,108	3,175,171
Accumulated Other Comprehensive Loss	(62,141)	(65,282)
Treasury Stock	(317,771)	(317,771)
Common Stockholder's Equity	10,804,196	10,711,734
Total Capitalization	20,227,655	19,696,656
Total Liabilities and Capitalization	32,355,176	32,053,173
The Connecticut Light And Power Company [Member]
Current Assets:
Cash and Cash Equivalents	15,315	6,579
Receivables, Net	349,714	359,132
Accounts Receivable from Affiliated Companies	17,184	16,851
Unbilled Revenues	51,069	50,373
Materials, Supplies and Inventory	56,432	52,050
Regulatory Assets	370,083	335,526
Prepayments and Other Current Assets	52,406	52,670
Total Current Assets	912,203	873,181
Property, Plant and Equipment, Net	7,754,894	7,632,392
Deferred Debits and Other Assets:
Regulatory Assets	1,367,486	1,391,564
Other Long-Term Assets	140,157	137,907
Total Deferred Debits and Other Assets	1,507,643	1,529,471
Total Assets	10,174,740	10,035,044
Current Liabilities:
Notes Payable to Eversource Parent	3,400	80,100
Long-Term Debt – Current Portion	100,000	250,000
Accounts Payable	281,414	289,532
Accounts Payable to Affiliated Companies	67,250	88,075
Obligations to Third Party Suppliers	51,885	55,520
Regulatory Liabilities	58,946	47,055
Derivative Liabilities	70,739	77,765
Other Current Liabilities	127,869	120,399
Total Current Liabilities	761,503	1,008,446
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	2,037,638	1,987,661
Regulatory Liabilities	101,241	100,138
Derivative Liabilities	415,187	412,750
Accrued Pension and SERP	296,105	300,208
Other Long-Term Liabilities	123,931	123,244
Total Deferred Credits and Other Liabilities	2,974,102	2,924,001
Capitalization:
Long-Term Debt	2,813,151	2,516,010
Noncontrolling Interest - Preferred Stock of Subsidiaries	116,200	116,200
Common Shareholders' Equity:
Common Shares	60,352	60,352
Capital Surplus, Paid In	2,110,726	2,110,714
Retained Earnings	1,338,592	1,299,374
Accumulated Other Comprehensive Loss	114	(53)
Common Stockholder's Equity	3,509,784	3,470,387
Total Capitalization	6,439,135	6,102,597
Total Liabilities and Capitalization	10,174,740	10,035,044
NSTAR Electric Company [Member]
Current Assets:
Cash and Cash Equivalents	2,448	3,494
Receivables, Net	264,337	257,557
Accounts Receivable from Affiliated Companies	4,565	8,581
Unbilled Revenues	28,393	31,632
Taxes Receivable	2,884	39,738
Fuel, Materials, Supplies and Inventory	94,338	62,288
Regulatory Assets	276,476	289,400
Prepayments and Other Current Assets	17,109	14,906
Total Current Assets	690,550	707,596
Property, Plant and Equipment, Net	6,108,944	6,051,835
Deferred Debits and Other Assets:
Regulatory Assets	1,051,090	1,057,746
Prepaid PBOP	100,609	95,073
Other Long-Term Assets	63,371	60,572
Total Deferred Debits and Other Assets	1,215,070	1,213,391
Total Assets	8,014,564	7,972,822
Current Liabilities:
Notes Payable	174,500	126,500
Long-Term Debt – Current Portion	400,000	400,000
Accounts Payable	177,110	232,599
Accounts Payable to Affiliated Companies	96,924	91,532
Obligations to Third Party Suppliers	60,650	55,863
Renewable Portfolio Standards Compliance Obligations	94,800	75,571
Regulatory Liabilities	62,154	63,653
Other Current Liabilities	54,166	71,122
Total Current Liabilities	1,120,304	1,116,840
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,866,259	1,836,292
Regulatory Liabilities	390,458	391,823
Accrued Pension and SERP	99,491	111,827
Other Long-Term Liabilities	125,640	123,194
Total Deferred Credits and Other Liabilities	2,481,848	2,463,136
Capitalization:
Long-Term Debt	1,678,514	1,678,116
Noncontrolling Interest - Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,045,378	1,045,378
Retained Earnings	1,645,156	1,625,984
Accumulated Other Comprehensive Loss	364	368
Common Stockholder's Equity	2,690,898	2,671,730
Total Capitalization	4,412,412	4,392,846
Total Liabilities and Capitalization	8,014,564	7,972,822
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash and Cash Equivalents	7,743	4,646
Receivables, Net	81,899	84,450
Accounts Receivable from Affiliated Companies	2,098	4,185
Unbilled Revenues	42,784	41,004
Fuel, Materials, Supplies and Inventory	165,725	162,354
Regulatory Assets	111,274	117,240
Prepayments and Other Current Assets	9,423	28,908
Total Current Assets	420,946	442,787
Property, Plant and Equipment, Net	3,076,608	3,039,313
Deferred Debits and Other Assets:
Regulatory Assets	243,643	245,525
Other Long-Term Assets	42,797	37,720
Total Deferred Debits and Other Assets	286,440	283,245
Total Assets	3,783,994	3,765,345
Current Liabilities:
Notes Payable to Eversource Parent	144,900	160,900
Long-Term Debt – Current Portion	70,000	70,000
Accounts Payable	70,710	85,716
Accounts Payable to Affiliated Companies	40,463	29,154
Regulatory Liabilities	17,224	12,659
Other Current Liabilities	52,771	43,253
Total Current Liabilities	396,068	401,682
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	796,118	785,385
Regulatory Liabilities	45,600	44,779
Accrued Pension and SERP	91,911	94,652
Other Long-Term Liabilities	48,435	49,442
Total Deferred Credits and Other Liabilities	982,064	974,258
Capitalization:
Long-Term Debt	1,002,305	1,002,048
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	843,134	843,134
Retained Earnings	565,098	549,286
Accumulated Other Comprehensive Loss	(4,675)	(5,063)
Common Stockholder's Equity	1,403,557	1,387,357
Total Capitalization	2,405,862	2,389,405
Total Liabilities and Capitalization	3,783,994	3,765,345
Western Massachusetts Electric Company [Member]
Current Assets:
Cash and Cash Equivalents	769	0
Receivables, Net	57,340	54,940
Accounts Receivable from Affiliated Companies	16,588	14,425
Unbilled Revenues	16,850	15,329
Fuel, Materials, Supplies and Inventory	9,911	8,618
Regulatory Assets	66,033	64,123
Prepayments and Other Current Assets	3,365	2,595
Total Current Assets	170,856	160,030
Property, Plant and Equipment, Net	1,694,818	1,678,262
Deferred Debits and Other Assets:
Regulatory Assets	123,317	127,291
Other Long-Term Assets	31,171	29,062
Total Deferred Debits and Other Assets	154,488	156,353
Total Assets	2,020,162	1,994,645
Current Liabilities:
Notes Payable to Eversource Parent	71,400	51,000
Accounts Payable	44,023	56,036
Accounts Payable to Affiliated Companies	14,837	19,478
Obligations to Third Party Suppliers	9,705	10,508
Renewable Portfolio Standards Compliance Obligations	25,110	20,383
Regulatory Liabilities	12,897	14,888
Other Current Liabilities	7,659	14,984
Total Current Liabilities	185,631	187,277
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	507,203	490,793
Regulatory Liabilities	19,119	17,227
Accrued Pension and SERP	18,660	20,390
Other Long-Term Liabilities	44,177	41,308
Total Deferred Credits and Other Liabilities	589,159	569,718
Capitalization:
Long-Term Debt	566,415	566,536
Common Shareholders' Equity:
Common Shares	10,866	10,866
Capital Surplus, Paid In	444,398	444,398
Retained Earnings	225,930	218,212
Accumulated Other Comprehensive Loss	(2,237)	(2,362)
Common Stockholder's Equity	678,957	671,114
Total Capitalization	1,245,372	1,237,650
Total Liabilities and Capitalization	$ 2,020,162	$ 1,994,645

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Revenues	$ 2,105,135	$ 2,055,635
Operating Expenses:
Purchased Power, Fuel and Transmission	753,649	754,859
Operations and Maintenance	330,265	320,136
Depreciation	186,805	173,986
Amortization of Regulatory Assets, Net	24,017	20,997
Energy Efficiency Programs	146,158	137,175
Taxes Other Than Income Taxes	155,222	159,946
Total Operating Expenses	1,596,116	1,567,099
Operating Income/(Loss)	509,019	488,536
Interest Expense	103,429	98,212
Other Income/(Loss), Net	13,577	2,011
Income Before Income Tax Expense	419,167	392,335
Income Tax Expense	157,829	146,302
Net Income	261,338	246,033
Net Income Attributable to Noncontrolling Interests	1,880	1,880
Net Income Attributable to Common Shareholders	$ 259,458	$ 244,153
Dividends Declared Per Common Share (in dollars per share)	$ 0.48	$ 0.45
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,463,151	317,517,141
Diluted (in shares)	318,124,536	318,481,050
The Connecticut Light And Power Company [Member]
Operating Revenues	$ 732,310	$ 735,317
Operating Expenses:
Purchased Power, Fuel and Transmission	244,938	272,600
Operations and Maintenance	128,226	110,843
Depreciation	59,751	56,969
Amortization of Regulatory Assets, Net	12,803	9,878
Energy Efficiency Programs	36,591	38,090
Taxes Other Than Income Taxes	73,979	75,465
Total Operating Expenses	556,288	563,845
Operating Income/(Loss)	176,022	171,472
Interest Expense	34,964	36,498
Other Income/(Loss), Net	2,756	936
Income Before Income Tax Expense	143,814	135,910
Income Tax Expense	53,606	48,863
Net Income	90,208	87,047
NSTAR Electric Company [Member]
Operating Revenues	603,779	614,216
Operating Expenses:
Purchased Power, Fuel and Transmission	233,093	254,336
Operations and Maintenance	88,351	94,696
Depreciation	55,216	51,886
Amortization of Regulatory Assets, Net	4,977	4,683
Energy Efficiency Programs	67,312	66,243
Taxes Other Than Income Taxes	27,393	32,555
Total Operating Expenses	476,342	504,399
Operating Income/(Loss)	127,437	109,817
Interest Expense	22,029	20,889
Other Income/(Loss), Net	3,249	(334)
Income Before Income Tax Expense	108,657	88,594
Income Tax Expense	42,495	34,101
Net Income	66,162	54,493
Public Service Company Of New Hampshire [Member]
Operating Revenues	253,157	242,290
Operating Expenses:
Purchased Power, Fuel and Transmission	61,747	50,214
Operations and Maintenance	62,351	59,213
Depreciation	30,735	28,235
Amortization of Regulatory Assets, Net	5,445	8,518
Energy Efficiency Programs	3,746	3,620
Taxes Other Than Income Taxes	20,881	21,795
Total Operating Expenses	184,905	171,595
Operating Income/(Loss)	68,252	70,695
Interest Expense	12,808	12,461
Other Income/(Loss), Net	1,198	150
Income Before Income Tax Expense	56,642	58,384
Income Tax Expense	22,330	22,326
Net Income	34,312	36,058
Western Massachusetts Electric Company [Member]
Operating Revenues	130,136	128,095
Operating Expenses:
Purchased Power, Fuel and Transmission	40,867	39,563
Operations and Maintenance	22,498	21,805
Depreciation	12,002	11,371
Amortization of Regulatory Asset (Liability)	(488)	1,212
Energy Efficiency Programs	10,664	10,856
Taxes Other Than Income Taxes	10,428	10,232
Total Operating Expenses	95,971	95,039
Operating Income/(Loss)	34,165	33,056
Interest Expense	6,249	6,004
Other Income/(Loss), Net	77	(149)
Income Before Income Tax Expense	27,993	26,903
Income Tax Expense	10,775	10,076
Net Income	$ 17,218	$ 16,827

CONDENSED CONSOLIDATED STATEME4

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Income	$ 261,338	$ 246,033
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	534	534
Changes in Unrealized Gains/(Losses) on Marketable Securities	1,645	264
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	962	871
Net OCI	3,141	1,669
Comprehensive Income Attributable to Noncontrolling Interests	(1,880)	(1,880)
Comprehensive Income Attributable to Common Shareholders	262,599	245,822
The Connecticut Light And Power Company [Member]
Net Income	90,208	87,047
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	111	111
Changes in Unrealized Gains/(Losses) on Marketable Securities	56	9
Net OCI	167	120
Comprehensive Income Attributable to Common Shareholders	90,375	87,167
NSTAR Electric Company [Member]
Net Income	66,162	54,493
Other Comprehensive (Loss)/Income, Net of Tax:
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	(4)	(10)
Net OCI	(4)	(10)
Comprehensive Income Attributable to Common Shareholders	66,158	54,483
Public Service Company Of New Hampshire [Member]
Net Income	34,312	36,058
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	291	290
Changes in Unrealized Gains/(Losses) on Marketable Securities	97	16
Net OCI	388	306
Comprehensive Income Attributable to Common Shareholders	34,700	36,364
Western Massachusetts Electric Company [Member]
Net Income	17,218	16,827
Other Comprehensive (Loss)/Income, Net of Tax:
Qualified Cash Flow Hedging Instruments	109	109
Changes in Unrealized Gains/(Losses) on Marketable Securities	16	3
Net OCI	125	112
Comprehensive Income Attributable to Common Shareholders	$ 17,343	$ 16,939

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities:
Net Income	$ 261,338	$ 246,033
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	186,805	173,986
Deferred Income Taxes	141,398	141,132
Pension, SERP and PBOP Expense, Net	5,828	11,583
Pension and PBOP Contributions	(45,700)	(30,383)
Regulatory Over/(Under) Recoveries, Net	56,734	(82,772)
Amortization of Regulatory Assets, Net	24,017	20,997
Other	(42,428)	(16,532)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(50,251)	(133,965)
Fuel, Materials, Supplies and Inventory	(33,058)	(22,748)
Taxes Receivable/Accrued, Net	32,313	279,106
Accounts Payable	(57,701)	(76,317)
Other Current Assets and Liabilities, Net	(42,793)	(10,156)
Net Cash Flows Provided by Operating Activities	436,502	499,964
Investing Activities:
Investments in Property, Plant and Equipment	(523,560)	(431,472)
Proceeds from Sales of Marketable Securities	154,772	136,805
Purchases of Marketable Securities	(149,688)	(135,427)
Other Investing Activities	(11,281)	5,494
Net Cash Flows Used in Investing Activities	(529,757)	(424,600)
Financing Activities:
Cash Dividends on Common Shares	(150,521)	(141,157)
Cash Dividends on Preferred Stock	(1,880)	(1,880)
Decrease in Notes Payable	(173,000)	(391,453)
Issuance of Long-Term Debt	600,000	500,000
Retirements of Long-Term Debt	(150,000)	0
Other Financing Activities	(15,832)	(13,855)
Net Cash Flows Provided by/(Used in) Financing Activities	108,767	(48,345)
Net Increase in Cash and Cash Equivalents	15,512	27,019
Cash and Cash Equivalents - Beginning of Period	30,251	23,947
Cash and Cash Equivalents - End of Period	45,763	50,966
The Connecticut Light And Power Company [Member]
Operating Activities:
Net Income	90,208	87,047
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	59,751	56,969
Deferred Income Taxes	47,864	58,363
Regulatory Over/(Under) Recoveries, Net	(18,734)	(70,195)
Amortization of Regulatory Assets, Net	12,803	9,878
Other	(2,373)	2,216
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(1,280)	(37,501)
Taxes Receivable/Accrued, Net	32,920	141,951
Accounts Payable	(16,957)	(5,040)
Other Current Assets and Liabilities, Net	(32,576)	(22,533)
Net Cash Flows Provided by Operating Activities	171,626	221,155
Investing Activities:
Investments in Property, Plant and Equipment	(181,601)	(147,131)
Proceeds from the Sale of Property, Plant and Equipment	0	9,047
Other Investing Activities	32	49
Net Cash Flows Used in Investing Activities	(181,569)	(138,035)
Financing Activities:
Cash Dividends on Common Shares	(49,600)	(49,900)
Capital Contributions from Eversource Parent	0	145,700
Cash Dividends on Preferred Stock	(1,390)	(1,390)
Decrease in Notes Payable to Eversource Parent	(76,700)	(161,900)
Issuance of Long-Term Debt	300,000	0
Retirements of Long-Term Debt	(150,000)	0
Other Financing Activities	(3,631)	(205)
Net Cash Flows Provided by/(Used in) Financing Activities	18,679	(67,695)
Net Increase in Cash and Cash Equivalents	8,736	15,425
Cash and Cash Equivalents - Beginning of Period	6,579	1,057
Cash and Cash Equivalents - End of Period	15,315	16,482
NSTAR Electric Company [Member]
Operating Activities:
Net Income	66,162	54,493
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	55,216	51,886
Deferred Income Taxes	29,199	32,878
Pension and PBOP Contributions, Net of Pension, SERP and PBOP Expense	(10,422)	(12,953)
Regulatory Over/(Under) Recoveries, Net	4,373	(16,746)
Amortization of Regulatory Assets, Net	4,977	4,683
Other	(3,691)	(3,245)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(2,376)	(29,132)
Fuel, Materials, Supplies and Inventory	(32,050)	(40,322)
Taxes Receivable/Accrued, Net	38,970	33,938
Accounts Payable	(19,025)	1,187
Other Current Assets and Liabilities, Net	2,371	19,600
Net Cash Flows Provided by Operating Activities	133,704	96,267
Investing Activities:
Investments in Property, Plant and Equipment	(132,105)	(91,319)
Other Investing Activities	(3,617)	0
Net Cash Flows Used in Investing Activities	(135,722)	(91,319)
Financing Activities:
Cash Dividends on Common Shares	(46,500)	(90,300)
Cash Dividends on Preferred Stock	(490)	(490)
Decrease in Notes Payable	48,000	86,000
Other Financing Activities	(38)	0
Net Cash Flows Provided by/(Used in) Financing Activities	972	(4,790)
Net Increase in Cash and Cash Equivalents	(1,046)	158
Cash and Cash Equivalents - Beginning of Period	3,494	3,346
Cash and Cash Equivalents - End of Period	2,448	3,504
Public Service Company Of New Hampshire [Member]
Operating Activities:
Net Income	34,312	36,058
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	30,735	28,235
Deferred Income Taxes	11,290	21,181
Regulatory Over/(Under) Recoveries, Net	3,507	(2,291)
Amortization of Regulatory Assets, Net	5,445	8,518
Other	(4,471)	(9,166)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	1,149	(17,207)
Fuel, Materials, Supplies and Inventory	(3,371)	6,903
Taxes Receivable/Accrued, Net	1,778	57,935
Accounts Payable	5,475	2,100
Other Current Assets and Liabilities, Net	27,332	24,021
Net Cash Flows Provided by Operating Activities	113,181	156,287
Investing Activities:
Investments in Property, Plant and Equipment	(75,327)	(72,338)
Other Investing Activities	(145)	84
Net Cash Flows Used in Investing Activities	(75,472)	(72,254)
Financing Activities:
Cash Dividends on Common Shares	(18,500)	(19,400)
Capital Contributions from Eversource Parent	0	11,500
Decrease in Notes Payable to Eversource Parent	(16,000)	(74,200)
Other Financing Activities	(112)	(86)
Net Cash Flows Provided by/(Used in) Financing Activities	(34,612)	(82,186)
Net Increase in Cash and Cash Equivalents	3,097	1,847
Cash and Cash Equivalents - Beginning of Period	4,646	1,733
Cash and Cash Equivalents - End of Period	7,743	3,580
Western Massachusetts Electric Company [Member]
Operating Activities:
Net Income	17,218	16,827
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	12,002	11,371
Deferred Income Taxes	16,176	9,921
Regulatory Over/(Under) Recoveries, Net	(452)	(6,100)
Amortization of Regulatory (Liabilities)/Assets, Net	(488)	1,212
Other	(326)	(541)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(5,924)	2,197
Taxes Receivable/Accrued, Net	(1,404)	26,976
Accounts Payable	(10,141)	(11,011)
Other Current Assets and Liabilities, Net	(4,057)	(136)
Net Cash Flows Provided by Operating Activities	22,604	50,716
Investing Activities:
Investments in Property, Plant and Equipment	(32,744)	(39,891)
Other Investing Activities	9	13
Net Cash Flows Used in Investing Activities	(32,735)	(39,878)
Financing Activities:
Cash Dividends on Common Shares	(9,500)	(9,500)
Decrease in Notes Payable to Eversource Parent	20,400	100
Other Financing Activities	0	(3)
Net Cash Flows Provided by/(Used in) Financing Activities	10,900	(9,403)
Net Increase in Cash and Cash Equivalents	769	1,435
Cash and Cash Equivalents - Beginning of Period	0	834
Cash and Cash Equivalents - End of Period	$ 769	$ 2,269

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2017
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, PSNH, WMECO, Yankee Gas and NSTAR Gas. Eversource provides energy delivery service to approximately 3.7 million electric and natural gas customers through these six regulated utilities in Connecticut, Massachusetts and New Hampshire. 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 and WMECO 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 2016 Form 10-K, which was filed with the SEC. 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, PSNH's and WMECO's financial position as of March 31, 2017 and December 31, 2016 , and the results of operations, comprehensive income and cash flows for the three months ended March 31, 2017 and 2016 . The results of operations, comprehensive income and cash flows for the three months ended March 31, 2017 and 2016 are not necessarily indicative of the results expected for a full year. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's, PSNH's and WMECO's combined ownership interest in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and WMECO and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource's utility subsidiaries' distribution (including generation assets) 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. 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 May 2014, the Financial Accounting Standards Board ("FASB") issued an Accounting Standards Update ("ASU") 2014-09, Revenue from Contracts with Customers , which amends existing revenue recognition guidance and is required to be applied retrospectively (either to each reporting period presented or cumulatively at the date of initial application). The Company is evaluating the requirements and potential impacts of ASU 2014-09 and will implement the standard in the first quarter of 2018 cumulatively at the date of initial application. The guidance continues to be interpreted on an industry specific level, including the timing of recognizing revenues from billings to protected customers that may not meet the collectability threshold for revenue recognition. Therefore, while the effects of implementing the ASU on results of operations are not expected to be material, there may be changes in the timing of revenue recognition on the financial statements of Eversource, CL&P, NSTAR Electric, PSNH and WMECO. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Liabilities , which is required to be implemented in the first quarter of 2018. The ASU will remove the available-for-sale designation for equity securities, whereby changes in fair value are recorded in accumulated other comprehensive income within shareholders' equity, and will require changes in fair value of all equity securities to be recorded in earnings beginning on January 1, 2018, with the unrealized gain or loss on available-for-sale equity securities as of that date reclassified to retained earnings as a cumulative effect of adoption. The fair value of available-for-sale equity securities subject to this guidance as of March 31, 2017 was approximately $49 million . The remaining available-for-sale equity securities included in marketable securities on the balance sheet are held in nuclear decommissioning trusts and are subject to regulatory accounting treatment and will not be impacted by this guidance. Implementation of the ASU for other financial instruments is not expected to have a material impact on the financial statements of Eversource, CL&P, NSTAR Electric, PSNH and WMECO. In February 2016, the FASB issued ASU 2016-02, Leases , which changes existing lease accounting guidance and is required to be applied in the first quarter of 2019, with earlier application permitted. The ASU is required to be implemented for leases beginning on the date of initial application. For prior periods presented, leases are required to be recognized and measured using a modified retrospective approach. The Company is reviewing the requirements of ASU 2016-02, including balance sheet recognition of leases previously deemed operating leases, and expects to implement the ASU in the first quarter of 2019. In March 2017, the FASB issued ASU 2017-07, Compensation – Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , required to be implemented in the first quarter of 2018. The ASU requires separate presentation of service cost from other components of net pension and PBOP costs, with the other components presented as non-operating income and not subject to capitalization. The Company is assessing the impacts of the ASU on the financial statements of Eversource, CL&P, NSTAR Electric, PSNH and WMECO, however implementation of the ASU is not expected to have a material impact on the net income of Eversource, CL&P, NSTAR Electric, PSNH and WMECO. C. Provision for Uncollectible Accounts Eversource, including CL&P, NSTAR Electric, PSNH and WMECO, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectability from customers. Management continuously assesses the collectability of receivables and adjusts collectability estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the customer accounts are terminated and these balances are deemed to be uncollectible. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows WMECO and NSTAR Gas also to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. Certain of NSTAR Electric's uncollectible hardship accounts receivable are expected to be recovered in future rates, similar to WMECO and NSTAR Gas. These uncollectible customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets. The total provision for uncollectible accounts and for uncollectible hardship accounts, which is included in the total provision, is included in Receivables, Net on the balance sheets, and was as follows: Total Provision for Uncollectible Accounts Uncollectible Hardship (Millions of Dollars) As of March 31, 2017 As of December 31, 2016 As of March 31, 2017 As of December 31, 2016 Eversource $ 203.2 $ 200.6 $ 118.0 $ 119.9 CL&P 88.7 86.4 69.8 67.7 NSTAR Electric 52.6 54.8 23.7 26.2 PSNH 10.4 9.9 — — WMECO 14.2 15.5 8.2 9.9 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 and AROs, and the estimated fair value of preferred stock and long-term debt. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and Eversource's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below: Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products. Determination of Fair Value: The valuation techniques and inputs used in Eversource's fair value measurements are described in Note 4, "Derivative Instruments," Note 5, "Marketable Securities," and Note 10, "Fair Value of Financial Instruments," to the financial statements. E. Other Income, Net Items included within Other Income, Net on the statements of income primarily consist of investment income/(loss), interest income, AFUDC related to equity funds, and income/(loss) related to equity method investments. Investment income/(loss) primarily relates to debt and equity securities held in trust. For further information, see Note 5, "Marketable Securities," to the financial statements. F. Other Taxes Gross receipts taxes levied by the state of Connecticut are collected by CL&P and Yankee Gas from their respective customers. These gross receipts taxes are shown separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Three Months Ended (Millions of Dollars) March 31, 2017 March 31, 2016 Eversource $ 42.2 $ 42.2 CL&P 33.9 36.0 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 March 31, 2017 As of March 31, 2016 Eversource $ 220.5 $ 125.6 CL&P 104.2 52.6 NSTAR Electric 29.8 11.7 PSNH 28.7 26.8 WMECO 19.6 10.7

REGULATORY ACCOUNTING

REGULATORY ACCOUNTING	3 Months Ended
	Mar. 31, 2017
Regulated Operations [Abstract]
REGULATORY ACCOUNTING	REGULATORY ACCOUNTING Eversource's Regulated companies are subject to rate regulation that is based on cost recovery and meets the criteria for application of accounting guidance for rate-regulated operations, which considers the effect of regulation on the timing of the recognition of certain revenues and expenses. The Regulated companies' financial statements reflect the effects of the rate-making process. The rates charged to the customers of Eversource's Regulated companies are designed to collect each company's costs to provide service, including a return on investment. Management believes it is probable that each of the Regulated companies will recover its respective investments in long-lived assets, including regulatory assets. If management were to determine that it could no longer apply the accounting guidance applicable to rate-regulated enterprises to any of the Regulated companies' operations, or if management could not conclude it is probable that costs would be recovered from customers in future rates, the costs would be charged to net income in the period in which the determination is made. Regulatory Assets: The components of regulatory assets were as follows: Eversource As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) Benefit Costs $ 1,782.5 $ 1,817.8 Derivative Liabilities 416.3 423.3 Income Taxes, Net 645.4 644.5 Storm Restoration Costs 375.8 385.3 Goodwill-related 459.3 464.4 Regulatory Tracker Mechanisms 578.9 576.6 Contractual Obligations - Yankee Companies 70.6 84.9 Other Regulatory Assets 110.9 129.5 Total Regulatory Assets 4,439.7 4,526.3 Less: Current Portion 875.0 887.6 Total Long-Term Regulatory Assets $ 3,564.7 $ 3,638.7 As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Benefit Costs $ 421.5 $ 429.9 $ 181.1 $ 85.1 $ 429.3 $ 438.6 $ 184.2 $ 86.7 Derivative Liabilities 413.5 2.5 — — 420.5 2.8 — — Income Taxes, Net 435.9 90.4 23.4 30.9 437.0 89.7 24.2 30.8 Storm Restoration Costs 225.1 118.5 17.0 15.2 239.8 112.5 17.1 15.9 Goodwill-related — 394.3 — — — 398.7 — — Regulatory Tracker Mechanisms 170.5 245.9 101.8 49.1 123.9 257.3 104.5 46.7 Other Regulatory Assets 71.1 46.1 31.6 9.0 76.6 47.5 32.7 11.3 Total Regulatory Assets 1,737.6 1,327.6 354.9 189.3 1,727.1 1,347.1 362.7 191.4 Less: Current Portion 370.1 276.5 111.3 66.0 335.5 289.4 117.2 64.1 Total Long-Term Regulatory Assets $ 1,367.5 $ 1,051.1 $ 243.6 $ 123.3 $ 1,391.6 $ 1,057.7 $ 245.5 $ 127.3 Regulatory Costs in Other Long-Term Assets: Eversource's Regulated companies had $91.4 million (including $5.0 million for CL&P, $33.3 million for NSTAR Electric, $12.9 million for PSNH and $22.1 million for WMECO) and $86.3 million (including $5.9 million for CL&P, $35.0 million for NSTAR Electric, $8.2 million for PSNH, and $20.1 million for WMECO) of additional regulatory costs as of March 31, 2017 and December 31, 2016 , respectively, that were included in Other Long-Term Assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates. Regulatory Liabilities: The components of regulatory liabilities were as follows: Eversource As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) Cost of Removal $ 469.6 $ 459.7 Benefit Costs 130.8 136.2 Regulatory Tracker Mechanisms 188.8 145.3 AFUDC - Transmission 65.8 65.8 Other Regulatory Liabilities 37.2 42.1 Total Regulatory Liabilities 892.2 849.1 Less: Current Portion 199.2 146.8 Total Long-Term Regulatory Liabilities $ 693.0 $ 702.3 As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Cost of Removal $ 42.5 $ 273.3 $ 44.8 $ 10.6 $ 38.8 $ 271.6 $ 44.1 $ 8.6 Benefit Costs — 109.8 — — — 113.1 — — Regulatory Tracker Mechanisms 44.5 62.2 15.0 12.7 37.2 63.7 10.7 14.7 AFUDC - Transmission 49.9 7.2 — 8.7 50.2 6.9 — 8.7 Other Regulatory Liabilities 23.2 0.2 3.0 — 21.0 0.2 2.7 0.1 Total Regulatory Liabilities 160.1 452.7 62.8 32.0 147.2 455.5 57.5 32.1 Less: Current Portion 58.9 62.2 17.2 12.9 47.1 63.7 12.7 14.9 Total Long-Term Regulatory Liabilities $ 101.2 $ 390.5 $ 45.6 $ 19.1 $ 100.1 $ 391.8 $ 44.8 $ 17.2

PROPERTY, PLANT AND EQUIPMENT A

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION The following tables summarize utility property, plant and equipment by asset category: Eversource As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) Distribution - Electric $ 13,893.9 $ 13,716.9 Distribution - Natural Gas 3,049.3 3,010.4 Transmission - Electric 8,600.1 8,517.4 Generation 1,225.6 1,224.2 Electric and Natural Gas Utility 26,768.9 26,468.9 Other (1) 585.1 591.6 Property, Plant and Equipment, Gross 27,354.0 27,060.5 Less: Accumulated Depreciation Electric and Natural Gas Utility (6,607.5 ) (6,480.4 ) Other (251.3 ) (242.0 ) Total Accumulated Depreciation (6,858.8 ) (6,722.4 ) Property, Plant and Equipment, Net 20,495.2 20,338.1 Construction Work in Progress 1,146.7 1,012.4 Total Property, Plant and Equipment, Net $ 21,641.9 $ 21,350.5 (1) These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service. As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Distribution $ 5,628.7 $ 5,471.5 $ 1,981.9 $ 851.8 $ 5,562.9 $ 5,402.3 $ 1,949.8 $ 841.9 Transmission 3,930.1 2,462.8 1,075.5 1,083.4 3,912.9 2,435.8 1,059.3 1,061.1 Generation — — 1,189.6 36.0 — — 1,188.2 36.0 Property, Plant and Equipment, Gross 9,558.8 7,934.3 4,247.0 1,971.2 9,475.8 7,838.1 4,197.3 1,939.0 Less: Accumulated Depreciation (2,125.4 ) (2,064.4 ) (1,277.7 ) (347.0 ) (2,082.4 ) (2,025.4 ) (1,254.7 ) (338.8 ) Property, Plant and Equipment, Net 7,433.4 5,869.9 2,969.3 1,624.2 7,393.4 5,812.7 2,942.6 1,600.2 Construction Work in Progress 321.5 239.0 107.3 70.6 239.0 239.1 96.7 78.1 Total Property, Plant and Equipment, Net $ 7,754.9 $ 6,108.9 $ 3,076.6 $ 1,694.8 $ 7,632.4 $ 6,051.8 $ 3,039.3 $ 1,678.3

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	DERIVATIVE INSTRUMENTS The Regulated 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. The 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 or Operating Revenues 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 Regulated companies, regulatory assets or regulatory liabilities are recorded to offset the fair values of derivatives, as contract settlement amounts are recovered from, or refunded to, customers in their respective energy supply rates. The gross fair values of derivative assets and liabilities with the same counterparty are offset and reported as net Derivative Assets or Derivative Liabilities, with current and long-term portions, on the balance sheets. The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) 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: Level 2: Eversource $ 0.6 $ — $ 0.6 $ 6.0 $ — $ 6.0 Level 3: Eversource, CL&P 12.5 (8.6 ) 3.9 13.9 (9.4 ) 4.5 Long-Term Derivative Assets: Level 2: Eversource $ — $ — $ — $ 0.3 $ (0.1 ) $ 0.2 Level 3: Eversource, CL&P 78.3 (9.8 ) 68.5 77.3 (11.7 ) 65.6 Current Derivative Liabilities: Level 3: Eversource $ (72.9 ) $ — $ (72.9 ) $ (79.7 ) $ — $ (79.7 ) CL&P (70.7 ) — (70.7 ) (77.8 ) — (77.8 ) NSTAR Electric (2.2 ) — (2.2 ) (1.9 ) — (1.9 ) Long-Term Derivative Liabilities: Level 2: Eversource $ (0.3 ) $ — $ (0.3 ) $ — $ — $ — Level 3: Eversource (415.5 ) — (415.5 ) (413.7 ) — (413.7 ) CL&P (415.2 ) — (415.2 ) (412.8 ) — (412.8 ) NSTAR Electric (0.3 ) — (0.3 ) (0.9 ) — (0.9 ) (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists. For further information on the fair value of derivative contracts, see Note 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 capacity of these contracts is 787 MW. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the capacity market price received in the ISO-NE capacity markets. In addition, CL&P has a contract to purchase 0.1 million MWh of energy per year through 2020. NSTAR Electric has a renewable energy contract to purchase 0.1 million MWh of energy per year through 2018 and a capacity-related contract to purchase up to 35 MW per year through 2019. As of March 31, 2017 and December 31, 2016 , Eversource had New York Mercantile Exchange ("NYMEX") financial contracts for natural gas futures in order to reduce variability associated with the purchase price of approximately 5.4 million and 9.2 million MMBtu of natural gas, respectively. For the three months ended March 31, 2017 and 2016 , there were losses of $26.5 million and $30.5 million , respectively, deferred as regulatory costs, which reflect the change in fair value associated with Eversource's derivative contracts. Fair Value Measurements of Derivative Instruments Derivative contracts classified as Level 2 in the fair value hierarchy relate to the financial contracts for natural gas futures. Prices are obtained from broker quotes and are based on actual market activity. The contracts are valued using NYMEX natural gas prices. Valuations of these contracts also incorporate discount rates using the yield curve approach. The fair value of derivative contracts classified as Level 3 utilizes significant unobservable inputs. The fair value is modeled using income techniques, such as discounted cash flow valuations adjusted for assumptions relating to exit price. Significant observable inputs for valuations of these contracts include energy and energy-related product prices in future years for which quoted prices in an active market exist. Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements. The future power and capacity prices for periods that are not quoted in an active market or established at auction are based on available market data and are escalated based on estimates of inflation in order to address the full term of the contract. Valuations of derivative contracts using a discounted cash flow methodology include assumptions regarding the timing and likelihood of scheduled payments and also reflect non-performance risk, including credit, using the default probability approach based on the counterparty's credit rating for assets and the Company's credit rating for liabilities. Valuations incorporate estimates of premiums or discounts that would be required by a market participant to arrive at an exit price, using historical market transactions adjusted for the terms of the contract. The following is a summary of Eversource's, including CL&P's and NSTAR Electric's, Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of March 31, 2017 As of December 31, 2016 Range Period Covered Range Period Covered Capacity Prices: Eversource, CL&P $ 5.00 — 8.70 per kW-Month 2020 - 2026 $ 5.50 — 8.70 per kW-Month 2020 - 2026 Forward Reserve: Eversource, CL&P $ 1.40 — 2.00 per kW-Month 2017 - 2024 $ 1.40 — 2.00 per kW-Month 2017 - 2024 REC Prices: Eversource, NSTAR Electric $ 27.00 — 30.00 per REC 2017 - 2018 $ 24.00 — 29.00 per REC 2017 - 2018 Exit price premiums of 2 percent through 19 percent are also applied on these contracts and reflect the uncertainty and illiquidity premiums that would be required based on the most recent market activity available for similar type contracts. Significant increases or decreases in future energy or capacity prices in isolation would decrease or increase, respectively, the fair value of the derivative liability. Any increases in risk premiums would increase the fair value of the derivative liability. Changes in these fair values are recorded as a regulatory asset or liability and do not impact net income. Valuations using significant unobservable inputs: The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. For the Three Months Ended March 31, 2017 2016 (Millions of Dollars) Eversource CL&P NSTAR Eversource CL&P NSTAR Derivatives, Net: Fair Value as of Beginning of Period $ (423.3 ) $ (420.5 ) $ (2.8 ) $ (380.9 ) $ (380.8 ) $ (0.1 ) Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities (15.4 ) (14.6 ) (0.8 ) (28.9 ) (24.6 ) (4.3 ) Settlements 22.7 21.6 1.1 22.1 20.3 1.8 Fair Value as of End of Period $ (416.0 ) $ (413.5 ) $ (2.5 ) $ (387.7 ) $ (385.1 ) $ (2.6 )

MARKETABLE SECURITIES

MARKETABLE SECURITIES	3 Months Ended
	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
MARKETABLE SECURITIES	MARKETABLE SECURITIES Eversource maintains trusts that hold marketable securities to fund certain non-qualified executive benefits. These trusts are not subject to regulatory oversight by state or federal agencies. CYAPC and YAEC maintain legally restricted trusts, each of which holds marketable securities, to fund the spent nuclear fuel removal obligations of their nuclear fuel storage facilities. Trading Securities: Eversource has elected to record certain equity securities as trading securities, with the changes in fair values recorded in Other Income, Net on the statements of income. As of December 31, 2016 , these securities were classified as Level 1 in the fair value hierarchy and totaled $9.6 million . These securities were sold during the first quarter of 2017 and were no longer held as of March 31, 2017. For the three months ended March 31, 2016 , net gains on these securities of $0.2 million were recorded in Other Income, Net on the statement of income. Dividend income is recorded in Other Income, Net when dividends are declared. Available-for-Sale Securities: The following is a summary of available-for-sale securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of March 31, 2017 As of December 31, 2016 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 $ 296.9 $ 2.4 $ (1.3 ) $ 298.0 $ 296.2 $ 1.1 $ (2.1 ) $ 295.2 Equity Securities 201.9 77.8 (0.5 ) 279.2 203.3 62.3 (1.2 ) 264.4 Eversource's debt and equity securities include CYAPC's and YAEC's marketable securities held in nuclear decommissioning trusts in the amounts of $482.3 million and $466.7 million as of March 31, 2017 and December 31, 2016 , respectively. Unrealized gains and losses for these nuclear decommissioning trusts 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. Unrealized Losses and Other-than-Temporary Impairment: There have been no significant unrealized losses, other-than-temporary impairments or credit losses for the three months ended March 31, 2017 and 2016 . Factors considered in determining whether a credit loss exists include the duration and severity of the impairment, adverse conditions specifically affecting the issuer, and the payment history, ratings and rating changes of the security. For asset-backed debt securities, underlying collateral and expected future cash flows are also evaluated. Realized Gains and Losses: Realized gains and losses on available-for-sale securities are recorded in Other Income, Net for Eversource's non-qualified benefit trust and are offset in Other Long-Term Liabilities for CYAPC and YAEC. Eversource utilizes the specific identification basis method for the Eversource non-qualified benefit trust, and the average cost basis method for the CYAPC and YAEC nuclear decommissioning trusts to compute the realized gains and losses on the sale of available-for-sale securities. Contractual Maturities : As of March 31, 2017 , 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) $ 60.6 $ 60.6 One to five years 47.4 48.1 Six to ten years 54.7 55.3 Greater than ten years 134.2 134.0 Total Debt Securities $ 296.9 $ 298.0 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC nuclear decommissioning trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets. Fair Value Measurements: The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of March 31, 2017 As of December 31, 2016 Level 1: Mutual Funds and Equities $ 279.2 $ 274.0 Money Market Funds 56.2 54.8 Total Level 1 $ 335.4 $ 328.8 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 57.0 $ 63.0 Corporate Debt Securities 41.6 41.1 Asset-Backed Debt Securities 19.8 18.5 Municipal Bonds 112.5 107.5 Other Fixed Income Securities 10.9 10.3 Total Level 2 $ 241.8 $ 240.4 Total Marketable Securities $ 577.2 $ 569.2 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 instrument and also incorporating yield curves, credit spreads and specific bond terms and conditions. Asset-backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset-backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates, and tranche information. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.

SHORT-TERM AND LONG-TERM DEBT

SHORT-TERM AND LONG-TERM DEBT	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
SHORT-TERM AND LONG-TERM DEBT	SHORT-TERM AND LONG-TERM DEBT Commercial Paper Programs and Credit Agreements : Eversource parent has a $1.45 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. As of March 31, 2017 and December 31, 2016 , Eversource parent had $801.0 million and approximately $1.0 billion , respectively, in short-term borrowings outstanding under the Eversource parent commercial paper program, leaving $649.0 million and $428.0 million of available borrowing capacity as of March 31, 2017 and December 31, 2016 , respectively. The weighted-average interest rate on these borrowings as of March 31, 2017 and December 31, 2016 was 1.12 percent and 0.88 percent , respectively. As of March 31, 2017 , there were intercompany loans from Eversource parent of $3.4 million to CL&P, $144.9 million to PSNH, and $71.4 million to WMECO. As of December 31, 2016 , there were intercompany loans from Eversource parent of $80.1 million to CL&P, $160.9 million to PSNH and $51.0 million to WMECO. Eversource parent, CL&P, PSNH, WMECO, NSTAR Gas and Yankee Gas are parties to a five -year $1.45 billion revolving credit facility. The revolving credit facility's termination date is September 4, 2021. The revolving credit facility serves to backstop Eversource parent's $1.45 billion commercial paper program. There were no borrowings outstanding on the revolving credit facility as of March 31, 2017 or December 31, 2016 . NSTAR Electric has a $450 million commercial paper program allowing NSTAR Electric to issue commercial paper as a form of short-term debt. As of March 31, 2017 and December 31, 2016 , NSTAR Electric had $174.5 million and $126.5 million , respectively, in short-term borrowings outstanding under its commercial paper program, leaving $275.5 million and $323.5 million of available borrowing capacity as of March 31, 2017 and December 31, 2016 , respectively. The weighted-average interest rate on these borrowings as of March 31, 2017 and December 31, 2016 was 0.86 percent and 0.71 percent , respectively. NSTAR Electric is a party to a five -year $450 million revolving credit facility. The revolving credit facility's termination date is September 4, 2021. The revolving credit facility serves to backstop NSTAR Electric's $450 million commercial paper program. There were no borrowings outstanding on the revolving credit facility as of March 31, 2017 or December 31, 2016 . Amounts outstanding under the commercial paper programs are included in Notes Payable for Eversource and NSTAR Electric and are classified in current liabilities on the balance sheets as all borrowings are outstanding for no more than 364 days at one time. Intercompany loans from Eversource parent to CL&P, PSNH and WMECO are included in Notes Payable to Eversource Parent and are classified in current liabilities on their respective balance sheets. Intercompany loans from Eversource parent to CL&P, PSNH and WMECO are eliminated in consolidation on Eversource's balance sheets. Long-Term Debt Issuances: In March 2017, Eversource parent issued $300 million of 2.75 percent Series K Senior Notes due to mature in 2022. The proceeds, net of issuance costs, were used to repay short-term borrowings under the Eversource parent commercial paper program. In March 2017, CL&P issued $300 million of 3.20 percent 2017 Series A First and Refunding Mortgage Bonds due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings. Long-Term Debt Repayments: In March 2017, CL&P repaid at maturity the $150 million 5.375 percent 2007 Series A First and Refunding Mortgage Bonds, using short term borrowings. Long-Term Debt Issuance Authorizations: On January 4, 2017, PURA approved CL&P's request for authorization to issue up to $1.325 billion in long-term debt through December 31, 2020. On March 30, 2017, the DPU approved NSTAR Electric's request for authorization to issue up to $700 million in long-term debt through December 31, 2018.

PENSION BENEFITS AND POSTRETIRE

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS	3 Months Ended
	Mar. 31, 2017
Postemployment Benefits [Abstract]
PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS	PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS Eversource Service sponsors a defined benefit retirement plan ("Pension Plan") that covers eligible participants. In addition to the Pension Plan, Eversource maintains non-qualified defined benefit retirement plans sponsored by Eversource Service ("SERP Plans"), which provide benefits in excess of Internal Revenue Code limitations to eligible participants. Eversource Service also sponsors a defined benefit postretirement plan that provides 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 participants that met certain age and service eligibility requirements ("PBOP Plan"). In August 2016, the Company amended its PBOP Plan, which standardized separate benefit structures that existed within the plan and made other benefit changes. The remeasurement resulted in a prior service credit of $5.3 million for the three months ended March 31, 2017, which was reflected as a reduction to net periodic benefit expense for PBOP benefits. The majority of this amount will be deferred for future refund to customers. The components of net periodic benefit expense for the Pension, SERP and PBOP Plans are shown below. The net periodic benefit expense and the intercompany allocations, less the capitalized portions of pension, SERP and PBOP amounts, are included in Operations and Maintenance expense on the statements of income. Capitalized amounts relate to employees working on capital projects and are included in Property, Plant and Equipment, Net on the balance sheets. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric, PSNH and WMECO does not include the intercompany allocations or the corresponding capitalized portion, as these amounts are cash settled on a short-term basis. Pension and SERP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2017 March 31, 2016 Service Cost $ 18.7 $ 19.4 Interest Cost 46.3 46.5 Expected Return on Pension Plan Assets (83.5 ) (79.6 ) Actuarial Loss 33.6 31.5 Prior Service Cost 1.1 0.9 Total Net Periodic Benefit Expense $ 16.2 $ 18.7 Capitalized Pension Expense $ 5.4 $ 6.1 PBOP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2017 March 31, 2016 Service Cost $ 2.4 $ 3.1 Interest Cost 7.2 9.7 Expected Return on Plan Assets (15.9 ) (15.7 ) Actuarial Loss 2.0 1.1 Prior Service Credit (5.3 ) (0.1 ) Total Net Periodic Benefit Income $ (9.6 ) $ (1.9 ) Capitalized PBOP Income $ (4.6 ) $ (0.9 ) Pension and SERP For the Three Months Ended March 31, 2017 For the Three Months Ended March 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Service Cost $ 4.8 $ 3.3 $ 2.5 $ 0.8 $ 5.0 $ 3.4 $ 2.5 $ 0.9 Interest Cost 10.5 8.3 5.2 2.1 10.6 8.3 5.1 2.1 Expected Return on Pension Plan Assets (18.0 ) (17.6 ) (9.9 ) (4.4 ) (18.2 ) (16.9 ) (9.7 ) (4.4 ) Actuarial Loss 6.9 8.6 2.8 1.5 6.7 8.4 2.5 1.4 Prior Service Cost 0.4 0.1 0.1 0.1 0.4 — 0.1 0.1 Total Net Periodic Benefit Expense $ 4.6 $ 2.7 $ 0.7 $ 0.1 $ 4.5 $ 3.2 $ 0.5 $ 0.1 Intercompany Allocations $ 2.5 $ 1.9 $ 0.8 $ 0.5 $ 3.3 $ 2.2 $ 1.0 $ 0.6 Capitalized Pension Expense $ 2.5 $ 1.7 $ 0.3 $ 0.1 $ 2.7 $ 1.8 $ 0.3 $ 0.2 PBOP For the Three Months Ended March 31, 2017 For the Three Months Ended March 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Service Cost $ 0.5 $ 0.4 $ 0.3 $ 0.1 $ 0.5 $ 0.9 $ 0.3 $ 0.1 Interest Cost 1.4 2.1 0.8 0.3 1.4 4.0 0.8 0.3 Expected Return on Plan Assets (2.4 ) (6.6 ) (1.3 ) (0.5 ) (2.6 ) (6.4 ) (1.4 ) (0.6 ) Actuarial Loss 0.2 0.9 0.1 — 0.2 0.2 0.1 — Prior Service Cost/(Credit) 0.3 (4.3 ) 0.1 — — — — — Total Net Periodic Benefit Income $ — $ (7.5 ) $ — $ (0.1 ) $ (0.5 ) $ (1.3 ) $ (0.2 ) $ (0.2 ) Intercompany Allocations $ (0.3 ) $ (0.3 ) $ (0.1 ) $ — $ 0.2 $ 0.1 $ — $ — Capitalized PBOP Income $ (0.1 ) $ (3.8 ) $ — $ — $ (0.2 ) $ (0.6 ) $ — $ (0.1 )

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES A. Environmental Matters Eversource, CL&P, NSTAR Electric, PSNH and WMECO 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, PSNH and WMECO have an active environmental auditing and training program and each believes it is substantially in compliance with all enacted laws and regulations. The number of environmental sites and related reserves for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: As of March 31, 2017 As of December 31, 2016 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 60 $ 58.2 61 $ 65.8 CL&P 14 5.3 14 4.9 NSTAR Electric 13 1.0 13 3.2 PSNH 11 5.3 11 5.3 WMECO 4 0.7 4 0.6 Included in the Eversource number of sites and reserve amounts above are former MGP sites that were operated several decades ago and manufactured gas from coal and other processes, which resulted in certain by-products remaining in the environment that may pose a potential risk to human health and the environment, for which Eversource may have potential liability. The reserve balances related to these former MGP sites were $53.0 million and $59.0 million as of March 31, 2017 and December 31, 2016 , respectively, and related primarily to the natural gas business segment. The reduction in the reserve balance at the MGP sites was primarily due to a change in cost estimates at one site. 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, PSNH's, and WMECO's responsibility for remediation or the extent of remediation required, recently enacted laws and regulations, or changes in cost estimates due to certain economic factors. It is possible that new information or future developments could require a reassessment of the potential exposure to related environmental matters. As this information becomes available, management will continue to assess the potential exposure and adjust the reserves accordingly. B. Guarantees and Indemnifications In the normal course of business, Eversource parent provides credit assurances on behalf of its subsidiaries, including CL&P, NSTAR Electric, PSNH and WMECO, in the form of guarantees. Eversource parent issued a declining balance guaranty on behalf of Eversource Gas Transmission LLC, a wholly-owned subsidiary, to guarantee the payment of the subsidiary's capital contributions for its investment in the Access Northeast project. The guaranty will not exceed $206 million and decreases as capital contributions are made. The guaranty will expire upon the earlier of the full performance of the guaranteed obligations or December 31, 2021. Eversource parent issued a guaranty on behalf of its subsidiary, NPT, under which, beginning at the time the Northern Pass Transmission line goes into commercial operation, Eversource parent will guarantee the financial obligations of NPT under the TSA with HQ in an amount not to exceed $25 million . Eversource parent's obligations under the guaranty expire upon the full, final and indefeasible payment of the guaranteed obligations. Eversource parent has also entered into a guaranty on behalf of NPT under which Eversource parent will guarantee NPT's obligations under a facility with a financial institution pursuant to which NPT may request letters of credit in an aggregate amount of up to approximately $14 million . Eversource parent has also guaranteed certain indemnification and other obligations as a result of the sales of former unregulated subsidiaries and the termination of an unregulated business, with maximum exposures either not specified or not material. Management does not anticipate a material impact to net income or cash flows as a result of these various guarantees and indemnifications. The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries to external parties, as of March 31, 2017 : Company Description Maximum Exposure (in millions) Expiration Dates On behalf of subsidiaries: Eversource Gas Transmission LLC Access Northeast Project Capital Contributions Guaranty $ 185.1 2021 Various Surety Bonds (1) 38.7 2017 - 2018 Eversource Service and Rocky River Realty Company Lease Payments for Vehicles and Real Estate 8.8 2019 - 2024 (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. C. FERC ROE Complaints Four separate complaints have been filed at the FERC by combinations of New England state attorneys general, state regulatory commissions, consumer advocates, consumer groups, municipal parties and other parties (collectively the "Complainants"). In each of the first three complaints, the Complainants challenged the NETOs' base ROE of 11.14 percent that had been utilized since 2005 and sought an order to reduce it prospectively from the date of the final FERC order and for the 15 -month complaint periods arising from the separate complaints. In the fourth complaint, filed April 29, 2016, the Complainants challenged the NETOs' base ROE of 10.57 percent and the maximum ROE for transmission incentive ("incentive cap") of 11.74 percent , asserting that these ROEs were unjust and unreasonable. In response to appeals of the FERC decision in the first complaint filed by the NETOs and the Complainants, the D.C. Circuit Court of Appeals (the "Court") issued a decision on April 14, 2017 vacating and remanding the FERC's decision. The Court found that the FERC failed to make an explicit finding that the prior 11.14 percent base ROE was unjust and unreasonable, as required under Section 206 of the Federal Power Act, before it could set a new base ROE. The Court also found that the FERC did not provide a rational connection between the record evidence and its decision to select the midpoint of the upper half of the zone of reasonableness for the new base ROE. A summary of the four separate complaints and the base ROEs pertinent to those complaints are as follows: Complaint 15-Month Time Period of Complaint (Beginning as of Complaint Filing Date) Original Base ROE Authorized by FERC at Time of Complaint Filing Date (1) Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (1) Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions) FERC ALJ Recommendation of Base ROE on Second and Third Complaints (Issued March 22, 2016) First 10/1/2011 - 12/31/2012 11.14% 10.57% $— (2) N/A Second 12/27/2012 - 3/26/2014 11.14% N/A 39.1 (3) 9.59% Third 7/31/2014 - 10/30/2015 11.14% 10.57% — 10.90% Fourth 4/29/2016 - 7/28/2017 10.57% 10.57% — N/A (1) The total ROE between October 1, 2011 and October 15, 2014 was within a range of 11.14 percent to 13.1 percent . In 2014, as a result of a FERC order, the incentive cap was set at 11.74 percent for the first complaint period and also effective from October 16, 2014 through April 14, 2017. (2) CL&P, NSTAR Electric, PSNH and WMECO have refunded all amounts associated with the first complaint period, totaling $38.9 million (pre-tax and excluding interest) at Eversource (including $22.4 million at CL&P, $8.4 million at NSTAR Electric, $2.8 million at PSNH, and $5.3 million at WMECO), reflecting both the base ROE and incentive cap prescribed by the FERC order. (3) The reserve represents the difference between the ROEs billed during the second complaint period and a 10.57 percent base ROE and 11.74 percent incentive cap. The reserve was $21.4 million for CL&P, $8.5 million for NSTAR Electric, $3.1 million for PSNH, and $6.1 million for WMECO as of March 31, 2017. At this time, the Company cannot reasonably estimate a range of gain or loss for the complaint proceedings. The Court decision did not provide a reasonable basis for a change to the March 31, 2017 reserve balance of $39.1 million (pre-tax and excluding interest) for the second complaint period, and the Company has not changed its reserves or recognized ROEs for any of the complaint periods. Management cannot at this time predict the ultimate effect of the Court decision on any of the complaint periods or the estimated impacts on the financial position, results of operations or cash flows of Eversource, CL&P, NSTAR Electric, PSNH and WMECO. The average impact of a 10 basis point change to the base ROE for each of the 15 -month complaint periods would affect Eversource's after-tax earnings by approximately $3 million . D. Eversource and NSTAR Electric Boston Harbor Civil Action On July 15, 2016, the United States Army Corps of Engineers filed a civil action in the United States District Court for the District of Massachusetts under provisions of the Rivers and Harbors Act of 1899 and the Clean Water Act against NSTAR Electric, Harbor Electric Energy Company, a wholly-owned subsidiary of NSTAR Electric ("HEEC"), and the Massachusetts Water Resources Authority (together with NSTAR Electric and HEEC, the "Defendants"). The action alleges that the Defendants failed to comply with certain permitting requirements relating to the placement of the HEEC-owned electric distribution cable beneath Boston Harbor. The action seeks an order to force HEEC to comply with cable depth requirements in the U.S. Army Corps of Engineers' permit or alternatively to remove the electric distribution cable and cease unauthorized work in U.S. waterways. The action also seeks civil penalties and other costs. Management believes there are valid defenses to the claims and is defending NSTAR Electric and HEEC vigorously. Concurrently, NSTAR Electric and HEEC are seeking to work collaboratively with all parties for a mutually beneficial resolution. At this time, management is unable to predict the outcome of this action or the impact on Eversource's and NSTAR Electric's financial position, results of operations, or cash flows.

PSNH GENERATION ASSET SALE

PSNH GENERATION ASSET SALE	3 Months Ended
	Mar. 31, 2017
Regulated Operations [Abstract]
PSNH GENERATION ASSET SALE	PSNH GENERATION ASSET SALE On June 10, 2015, Eversource and PSNH entered into the 2015 Public Service Company of New Hampshire Restructuring and Rate Stabilization Agreement (the "Agreement") with the New Hampshire Office of Energy and Planning, certain members of the NHPUC staff, the Office of Consumer Advocate, two State Senators, and several other parties. Under the terms of the Agreement, PSNH agreed to divest its generation assets, subject to NHPUC approval. The Agreement provided for a resolution of issues pertaining to PSNH's generation assets in pending regulatory proceedings before the NHPUC. The Agreement provided for the Clean Air Project prudence proceeding to be resolved and all remaining Clean Air Project costs to be included in rates effective January 1, 2016. As part of the Agreement, PSNH agreed to forego recovery of $25 million of the equity return related to the Clean Air Project. In addition, PSNH will not seek a general distribution rate increase effective before July 1, 2017 and will contribute $5 million to create a clean energy fund, which will not be recoverable from its customers. On July 1, 2016, the NHPUC approved the Agreement in an order that, among other things, instructs PSNH to begin the process of divesting its generation assets. The NHPUC selected an auction adviser to assist with the divestiture, and the final plan and auction process were approved by the NHPUC in November 2016. An intervening appeal alleging that the auction process and schedule were unreasonable was rejected by the New Hampshire Supreme Court in February 2017. In late March 2017, the formal divestiture process began. We continue to believe the assets will be sold by the end of 2017. The sales price of the generation assets could be less than the carrying value, but the Company believes that full recovery of PSNH's generation assets is probable through a combination of cash flows during the remaining operating period, sales proceeds upon divestiture, and recovery of stranded costs via bonds that will be secured by a non-bypassable charge or through recoveries in future rates billed to PSNH's customers. As of March 31, 2017 , PSNH's generation assets were as follows: (Millions of Dollars) Gross Plant $ 1,192.6 Accumulated Depreciation (564.1 ) Net Plant 628.5 Fuel 98.3 Materials and Supplies 48.5 Emission Allowances 19.7 Total Generation Assets $ 795.0 As of March 31, 2017 , current and long-term liabilities associated with PSNH's generation assets included Accounts Payable of $30.1 million , Other Current Liabilities of $21.7 million , AROs of $20.3 million , and Accrued Pension, SERP and PBOP of $23.7 million .

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS The following methods and assumptions were used to estimate the fair value of each of the following financial instruments: Preferred Stock and Long-Term Debt: The fair value of CL&P's and NSTAR Electric's preferred stock is based upon pricing models that incorporate interest rates and other market factors, valuations or trades of similar securities and cash flow projections. The fair value of long-term debt securities is based upon pricing models that incorporate quoted market prices for those issues or similar issues adjusted for market conditions, credit ratings of the respective companies and treasury benchmark yields. The fair values provided in the tables below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows: As of March 31, 2017 As of December 31, 2016 Eversource (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 156.6 $ 155.6 $ 158.3 Long-Term Debt 10,041.8 10,428.0 9,603.2 9,980.5 CL&P NSTAR Electric PSNH WMECO (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of March 31, 2017: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 113.5 $ 43.0 $ 43.1 $ — $ — $ — $ — Long-Term Debt 2,913.2 3,179.5 2,078.5 2,202.9 1,072.3 1,115.2 566.4 596.8 As of December 31, 2016: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 114.7 $ 43.0 $ 43.6 $ — $ — $ — $ — Long-Term Debt 2,766.0 3,049.6 2,078.1 2,201.6 1,072.0 1,109.7 566.5 589.0 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)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) The changes in accumulated other comprehensive income/(loss) by component, net of tax, is as follows: For the Three Months Ended March 31, 2017 For the Three Months Ended March 31, 2016 Qualified Unrealized Qualified Unrealized Cash Flow Gains Cash Flow Gains/(Losses) Eversource (Millions of Dollars) Hedging on Marketable Defined Hedging on Marketable Defined Instruments Securities Benefit Plans Total Instruments Securities Benefit Plans Total Balance as of Beginning of Period $ (8.2 ) $ 0.4 $ (57.5 ) $ (65.3 ) $ (10.3 ) $ (1.9 ) $ (54.6 ) $ (66.8 ) OCI Before Reclassifications — 1.7 — 1.7 — 0.2 — 0.2 Amounts Reclassified from AOCL 0.5 — 1.0 1.5 0.5 — 0.9 1.4 Net OCI 0.5 1.7 1.0 3.2 0.5 0.2 0.9 1.6 Balance as of End of Period $ (7.7 ) $ 2.1 $ (56.5 ) $ (62.1 ) $ (9.8 ) $ (1.7 ) $ (53.7 ) $ (65.2 ) Eversource's qualified cash flow hedging instruments represent interest rate swap agreements on debt issuances that were settled in prior years. The settlement amount was recorded in AOCL and is being amortized into Net Income over the term of the underlying debt instrument. CL&P, PSNH and WMECO continue to amortize interest rate swaps settled in prior years from AOCL into Interest Expense over the remaining life of the associated long-term debt. Such interest rate swaps are not material to their respective financial statements. Defined benefit plan OCI amounts before reclassifications relate to actuarial gains and losses and prior service costs that arose during the year and were recognized in AOCL. The unamortized actuarial gains and losses and prior service costs on the defined benefit plans are amortized from AOCL into Operations and Maintenance expense over the average future employee service period, and are reflected in amounts reclassified from AOCL. For further information, see Note 7, "Pension Benefits and Postretirement Benefits Other Than Pensions."

COMMON SHARES

COMMON SHARES	3 Months Ended
	Mar. 31, 2017
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, PSNH and WMECO that were authorized and issued, as well as the respective per share par values: Shares Authorized as of March 31, 2017 and Issued as of Par Value December 31, 2016 March 31, 2017 December 31, 2016 Eversource $ 5 380,000,000 333,878,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 100 100 PSNH $ 1 100,000,000 301 301 WMECO $ 25 1,072,471 434,653 434,653 As of both March 31, 2017 and December 31, 2016 , there were 16,992,594 Eversource common shares held as treasury shares. As of both March 31, 2017 and December 31, 2016 , Eversource common shares outstanding were 316,885,808 . COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS Dividends on the preferred stock of CL&P and NSTAR Electric totaled $1.9 million for each of the three months ended March 31, 2017 and 2016 . These dividends were presented as Net Income Attributable to Noncontrolling Interests on the Eversource statements of income. Noncontrolling Interest – Preferred Stock of Subsidiaries on the Eversource balance sheets totaled $155.6 million as of March 31, 2017 and December 31, 2016 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to the parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest.

COMMON SHAREHOLDERS' EQUITY AND

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	3 Months Ended
	Mar. 31, 2017
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, PSNH and WMECO that were authorized and issued, as well as the respective per share par values: Shares Authorized as of March 31, 2017 and Issued as of Par Value December 31, 2016 March 31, 2017 December 31, 2016 Eversource $ 5 380,000,000 333,878,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 100 100 PSNH $ 1 100,000,000 301 301 WMECO $ 25 1,072,471 434,653 434,653 As of both March 31, 2017 and December 31, 2016 , there were 16,992,594 Eversource common shares held as treasury shares. As of both March 31, 2017 and December 31, 2016 , Eversource common shares outstanding were 316,885,808 . COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS Dividends on the preferred stock of CL&P and NSTAR Electric totaled $1.9 million for each of the three months ended March 31, 2017 and 2016 . These dividends were presented as Net Income Attributable to Noncontrolling Interests on the Eversource statements of income. Noncontrolling Interest – Preferred Stock of Subsidiaries on the Eversource balance sheets totaled $155.6 million as of March 31, 2017 and December 31, 2016 . On the Eversource balance sheets, Common Shareholders' Equity was fully attributable to the parent and Noncontrolling Interest – Preferred Stock of Subsidiaries was fully attributable to the noncontrolling interest.

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic EPS is computed based upon the weighted average number of common shares outstanding during each period. Diluted EPS is computed on the basis of the weighted average number of common shares outstanding plus the potential dilutive effect of certain share-based compensation awards as if they were converted into common shares. The dilutive effect of unvested RSU and performance share awards and unexercised stock options is calculated using the treasury stock method. RSU and performance share awards are included in basic weighted average common shares outstanding as of the date that all necessary vesting conditions have been satisfied. For the three months ended March 31, 2017 and 2016 , there were no antidilutive share awards excluded from the computation of diluted EPS. The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended March 31, 2017 March 31, 2016 Net Income Attributable to Common Shareholders $ 259.5 $ 244.2 Weighted Average Common Shares Outstanding: Basic 317,463,151 317,517,141 Dilutive Effect 661,385 963,909 Diluted 318,124,536 318,481,050 Basic and Diluted EPS $ 0.82 $ 0.77

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Presentation: Eversource is organized among the Electric Distribution, Electric Transmission and Natural Gas 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 and natural gas primarily are derived from residential, commercial and industrial customers and are not dependent on any single customer. The Electric Distribution reportable segment includes the generation activities of PSNH and WMECO. The remainder of Eversource's operations is presented as Other in the tables below and primarily consists of 1) the equity in earnings of Eversource parent from its subsidiaries and intercompany interest income, both of which are eliminated in consolidation, and interest expense related to the debt of Eversource parent, 2) the revenues and expenses of Eversource Service, most of which are eliminated in consolidation, 3) the operations of CYAPC and YAEC, and 4) the results of other unregulated subsidiaries, which are not part of its core business. In addition, Other in the tables below includes Eversource parent's equity ownership interests in certain natural gas pipeline projects owned by Enbridge, Inc., the Bay State Wind project, an energy investment fund, and two companies that transmit hydroelectricity imported from the Hydro-Quebec system in Canada. In the ordinary course of business, Yankee Gas and NSTAR Gas purchase natural gas transmission services from the Enbridge, Inc. natural gas pipeline projects described above. These affiliate transaction costs total approximately $62.5 million annually and are classified as Purchased Power, Fuel and Transmission on the Eversource statements of income. Cash flows used for investments in plant included in the segment information below are cash capital expenditures that do not include amounts incurred but not paid, cost of removal, AFUDC related to equity funds, and the capitalized portions of pension expense. Eversource's 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. Each of Eversource's subsidiaries, including CL&P, NSTAR Electric, PSNH and WMECO, has one reportable segment. Eversource's operating segments and reporting units are consistent with its reportable business segments. Eversource's segment information is as follows: For the Three Months Ended March 31, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Other Eliminations Total Operating Revenues $ 1,401.1 $ 403.6 $ 316.9 $ 236.3 $ (252.8 ) $ 2,105.1 Depreciation and Amortization (129.8 ) (21.7 ) (50.6 ) (9.2 ) 0.5 (210.8 ) Other Operating Expenses (1,041.9 ) (289.6 ) (90.0 ) (216.6 ) 252.8 (1,385.3 ) Operating Income $ 229.4 $ 92.3 $ 176.3 $ 10.5 $ 0.5 $ 509.0 Interest Expense $ (48.2 ) $ (10.6 ) $ (28.1 ) $ (19.7 ) $ 3.2 $ (103.4 ) Other Income, Net 5.0 0.3 4.9 328.9 (325.5 ) 13.6 Net Income Attributable to Common Shareholders 114.1 50.8 94.2 322.2 (321.8 ) 259.5 Cash Flows Used for Investments in Plant 236.2 64.5 192.6 30.3 — 523.6 For the Three Months Ended March 31, 2016 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Other Eliminations Total Operating Revenues $ 1,436.1 $ 342.6 $ 283.3 $ 214.2 $ (220.6 ) $ 2,055.6 Depreciation and Amortization (127.7 ) (15.8 ) (45.1 ) (6.9 ) 0.5 (195.0 ) Other Operating Expenses (1,088.9 ) (233.5 ) (73.0 ) (197.3 ) 220.6 (1,372.1 ) Operating Income $ 219.5 $ 93.3 $ 165.2 $ 10.0 $ 0.5 $ 488.5 Interest Expense $ (48.0 ) $ (10.1 ) $ (28.0 ) $ (14.1 ) $ 2.0 $ (98.2 ) Other Income/(Loss), Net — (0.3 ) 2.6 305.5 (305.8 ) 2.0 Net Income Attributable to Common Shareholders 108.4 50.9 85.7 302.5 (303.3 ) 244.2 Cash Flows Used for Investments in Plant 184.2 52.1 172.4 22.8 — 431.5 The following table summarizes Eversource's segmented total assets: Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Other Eliminations Total As of March 31, 2017 $ 18,343.3 $ 3,332.7 $ 9,015.6 $ 14,590.4 $ (12,926.8 ) $ 32,355.2 As of December 31, 2016 18,367.5 3,303.8 8,751.5 14,493.1 (12,862.7 ) 32,053.2

SUMMARY OF SIGNIFICANT ACCOUN21

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2017
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, PSNH, WMECO, Yankee Gas and NSTAR Gas. Eversource provides energy delivery service to approximately 3.7 million electric and natural gas customers through these six regulated utilities in Connecticut, Massachusetts and New Hampshire. 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 and WMECO 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 2016 Form 10-K, which was filed with the SEC. 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, PSNH's and WMECO's financial position as of March 31, 2017 and December 31, 2016 , and the results of operations, comprehensive income and cash flows for the three months ended March 31, 2017 and 2016 . The results of operations, comprehensive income and cash flows for the three months ended March 31, 2017 and 2016 are not necessarily indicative of the results expected for a full year. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's, PSNH's and WMECO's combined ownership interest in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and WMECO and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource's utility subsidiaries' distribution (including generation assets) 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. 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 May 2014, the Financial Accounting Standards Board ("FASB") issued an Accounting Standards Update ("ASU") 2014-09, Revenue from Contracts with Customers , which amends existing revenue recognition guidance and is required to be applied retrospectively (either to each reporting period presented or cumulatively at the date of initial application). The Company is evaluating the requirements and potential impacts of ASU 2014-09 and will implement the standard in the first quarter of 2018 cumulatively at the date of initial application. The guidance continues to be interpreted on an industry specific level, including the timing of recognizing revenues from billings to protected customers that may not meet the collectability threshold for revenue recognition. Therefore, while the effects of implementing the ASU on results of operations are not expected to be material, there may be changes in the timing of revenue recognition on the financial statements of Eversource, CL&P, NSTAR Electric, PSNH and WMECO. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Liabilities , which is required to be implemented in the first quarter of 2018. The ASU will remove the available-for-sale designation for equity securities, whereby changes in fair value are recorded in accumulated other comprehensive income within shareholders' equity, and will require changes in fair value of all equity securities to be recorded in earnings beginning on January 1, 2018, with the unrealized gain or loss on available-for-sale equity securities as of that date reclassified to retained earnings as a cumulative effect of adoption. The fair value of available-for-sale equity securities subject to this guidance as of March 31, 2017 was approximately $49 million . The remaining available-for-sale equity securities included in marketable securities on the balance sheet are held in nuclear decommissioning trusts and are subject to regulatory accounting treatment and will not be impacted by this guidance. Implementation of the ASU for other financial instruments is not expected to have a material impact on the financial statements of Eversource, CL&P, NSTAR Electric, PSNH and WMECO. In February 2016, the FASB issued ASU 2016-02, Leases , which changes existing lease accounting guidance and is required to be applied in the first quarter of 2019, with earlier application permitted. The ASU is required to be implemented for leases beginning on the date of initial application. For prior periods presented, leases are required to be recognized and measured using a modified retrospective approach. The Company is reviewing the requirements of ASU 2016-02, including balance sheet recognition of leases previously deemed operating leases, and expects to implement the ASU in the first quarter of 2019. In March 2017, the FASB issued ASU 2017-07, Compensation – Retirement Benefits: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , required to be implemented in the first quarter of 2018. The ASU requires separate presentation of service cost from other components of net pension and PBOP costs, with the other components presented as non-operating income and not subject to capitalization. The Company is assessing the impacts of the ASU on the financial statements of Eversource, CL&P, NSTAR Electric, PSNH and WMECO
Provision for Uncollectible Accounts	Provision for Uncollectible Accounts Eversource, including CL&P, NSTAR Electric, PSNH and WMECO, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectability from customers. Management continuously assesses the collectability of receivables and adjusts collectability estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the customer accounts are terminated and these balances are deemed to be uncollectible. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows WMECO and NSTAR Gas also to recover in rates, amounts associated with certain uncollectible hardship accounts receivable. Certain of NSTAR Electric's uncollectible hardship accounts receivable are expected to be recovered in future rates, similar to WMECO and NSTAR Gas. These uncollectible customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets.
Fair Value Measurements	Fair Value Measurements Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases or normal sales" ("normal") and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill and AROs, and the estimated fair value of preferred stock and long-term debt. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and Eversource's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below: Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products.
Other Income, Net	Other Income, Net Items included within Other Income, Net on the statements of income primarily consist of investment income/(loss), interest income, AFUDC related to equity funds, and income/(loss) related to equity method investments. Investment income/(loss) primarily relates to debt and equity securities held in trust. For further information, see Note 5, "Marketable Securities," to the financial statements.
Other Taxes	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. Other Taxes Gross receipts taxes levied by the state of Connecticut are collected by CL&P and Yankee Gas from their respective customers.

SUMMARY OF SIGNIFICANT ACCOUN22

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	The total provision for uncollectible accounts and for uncollectible hardship accounts, which is included in the total provision, is included in Receivables, Net on the balance sheets, and was as follows: Total Provision for Uncollectible Accounts Uncollectible Hardship (Millions of Dollars) As of March 31, 2017 As of December 31, 2016 As of March 31, 2017 As of December 31, 2016 Eversource $ 203.2 $ 200.6 $ 118.0 $ 119.9 CL&P 88.7 86.4 69.8 67.7 NSTAR Electric 52.6 54.8 23.7 26.2 PSNH 10.4 9.9 — — WMECO 14.2 15.5 8.2 9.9
State Of Connecticut Gross Earnings Taxes	These gross receipts taxes are shown separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Three Months Ended (Millions of Dollars) March 31, 2017 March 31, 2016 Eversource $ 42.2 $ 42.2 CL&P 33.9 36.0
Schedule of Supplemental Cash Flow Information	Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of March 31, 2017 As of March 31, 2016 Eversource $ 220.5 $ 125.6 CL&P 104.2 52.6 NSTAR Electric 29.8 11.7 PSNH 28.7 26.8 WMECO 19.6 10.7

REGULATORY ACCOUNTING (Tables)

REGULATORY ACCOUNTING (Tables)	3 Months Ended
	Mar. 31, 2017
Regulated Operations [Abstract]
Schedule of Regulatory Assets	The components of regulatory assets were as follows: Eversource As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) Benefit Costs $ 1,782.5 $ 1,817.8 Derivative Liabilities 416.3 423.3 Income Taxes, Net 645.4 644.5 Storm Restoration Costs 375.8 385.3 Goodwill-related 459.3 464.4 Regulatory Tracker Mechanisms 578.9 576.6 Contractual Obligations - Yankee Companies 70.6 84.9 Other Regulatory Assets 110.9 129.5 Total Regulatory Assets 4,439.7 4,526.3 Less: Current Portion 875.0 887.6 Total Long-Term Regulatory Assets $ 3,564.7 $ 3,638.7 As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Benefit Costs $ 421.5 $ 429.9 $ 181.1 $ 85.1 $ 429.3 $ 438.6 $ 184.2 $ 86.7 Derivative Liabilities 413.5 2.5 — — 420.5 2.8 — — Income Taxes, Net 435.9 90.4 23.4 30.9 437.0 89.7 24.2 30.8 Storm Restoration Costs 225.1 118.5 17.0 15.2 239.8 112.5 17.1 15.9 Goodwill-related — 394.3 — — — 398.7 — — Regulatory Tracker Mechanisms 170.5 245.9 101.8 49.1 123.9 257.3 104.5 46.7 Other Regulatory Assets 71.1 46.1 31.6 9.0 76.6 47.5 32.7 11.3 Total Regulatory Assets 1,737.6 1,327.6 354.9 189.3 1,727.1 1,347.1 362.7 191.4 Less: Current Portion 370.1 276.5 111.3 66.0 335.5 289.4 117.2 64.1 Total Long-Term Regulatory Assets $ 1,367.5 $ 1,051.1 $ 243.6 $ 123.3 $ 1,391.6 $ 1,057.7 $ 245.5 $ 127.3
Schedule of Regulatory Liabilities	The components of regulatory liabilities were as follows: Eversource As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) Cost of Removal $ 469.6 $ 459.7 Benefit Costs 130.8 136.2 Regulatory Tracker Mechanisms 188.8 145.3 AFUDC - Transmission 65.8 65.8 Other Regulatory Liabilities 37.2 42.1 Total Regulatory Liabilities 892.2 849.1 Less: Current Portion 199.2 146.8 Total Long-Term Regulatory Liabilities $ 693.0 $ 702.3 As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Cost of Removal $ 42.5 $ 273.3 $ 44.8 $ 10.6 $ 38.8 $ 271.6 $ 44.1 $ 8.6 Benefit Costs — 109.8 — — — 113.1 — — Regulatory Tracker Mechanisms 44.5 62.2 15.0 12.7 37.2 63.7 10.7 14.7 AFUDC - Transmission 49.9 7.2 — 8.7 50.2 6.9 — 8.7 Other Regulatory Liabilities 23.2 0.2 3.0 — 21.0 0.2 2.7 0.1 Total Regulatory Liabilities 160.1 452.7 62.8 32.0 147.2 455.5 57.5 32.1 Less: Current Portion 58.9 62.2 17.2 12.9 47.1 63.7 12.7 14.9 Total Long-Term Regulatory Liabilities $ 101.2 $ 390.5 $ 45.6 $ 19.1 $ 100.1 $ 391.8 $ 44.8 $ 17.2

PROPERTY, PLANT AND EQUIPMENT24

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Tables)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Public Utility Property, Plant, and Equipment	The following tables summarize utility property, plant and equipment by asset category: Eversource As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) Distribution - Electric $ 13,893.9 $ 13,716.9 Distribution - Natural Gas 3,049.3 3,010.4 Transmission - Electric 8,600.1 8,517.4 Generation 1,225.6 1,224.2 Electric and Natural Gas Utility 26,768.9 26,468.9 Other (1) 585.1 591.6 Property, Plant and Equipment, Gross 27,354.0 27,060.5 Less: Accumulated Depreciation Electric and Natural Gas Utility (6,607.5 ) (6,480.4 ) Other (251.3 ) (242.0 ) Total Accumulated Depreciation (6,858.8 ) (6,722.4 ) Property, Plant and Equipment, Net 20,495.2 20,338.1 Construction Work in Progress 1,146.7 1,012.4 Total Property, Plant and Equipment, Net $ 21,641.9 $ 21,350.5 (1) These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service. As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Distribution $ 5,628.7 $ 5,471.5 $ 1,981.9 $ 851.8 $ 5,562.9 $ 5,402.3 $ 1,949.8 $ 841.9 Transmission 3,930.1 2,462.8 1,075.5 1,083.4 3,912.9 2,435.8 1,059.3 1,061.1 Generation — — 1,189.6 36.0 — — 1,188.2 36.0 Property, Plant and Equipment, Gross 9,558.8 7,934.3 4,247.0 1,971.2 9,475.8 7,838.1 4,197.3 1,939.0 Less: Accumulated Depreciation (2,125.4 ) (2,064.4 ) (1,277.7 ) (347.0 ) (2,082.4 ) (2,025.4 ) (1,254.7 ) (338.8 ) Property, Plant and Equipment, Net 7,433.4 5,869.9 2,969.3 1,624.2 7,393.4 5,812.7 2,942.6 1,600.2 Construction Work in Progress 321.5 239.0 107.3 70.6 239.0 239.1 96.7 78.1 Total Property, Plant and Equipment, Net $ 7,754.9 $ 6,108.9 $ 3,076.6 $ 1,694.8 $ 7,632.4 $ 6,051.8 $ 3,039.3 $ 1,678.3

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of March 31, 2017 As of December 31, 2016 (Millions of Dollars) 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: Level 2: Eversource $ 0.6 $ — $ 0.6 $ 6.0 $ — $ 6.0 Level 3: Eversource, CL&P 12.5 (8.6 ) 3.9 13.9 (9.4 ) 4.5 Long-Term Derivative Assets: Level 2: Eversource $ — $ — $ — $ 0.3 $ (0.1 ) $ 0.2 Level 3: Eversource, CL&P 78.3 (9.8 ) 68.5 77.3 (11.7 ) 65.6 Current Derivative Liabilities: Level 3: Eversource $ (72.9 ) $ — $ (72.9 ) $ (79.7 ) $ — $ (79.7 ) CL&P (70.7 ) — (70.7 ) (77.8 ) — (77.8 ) NSTAR Electric (2.2 ) — (2.2 ) (1.9 ) — (1.9 ) Long-Term Derivative Liabilities: Level 2: Eversource $ (0.3 ) $ — $ (0.3 ) $ — $ — $ — Level 3: Eversource (415.5 ) — (415.5 ) (413.7 ) — (413.7 ) CL&P (415.2 ) — (415.2 ) (412.8 ) — (412.8 ) NSTAR Electric (0.3 ) — (0.3 ) (0.9 ) — (0.9 ) (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists.
Fair Value Inputs, Liabilities, Quantitative Information	The following is a summary of Eversource's, including CL&P's and NSTAR Electric's, Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of March 31, 2017 As of December 31, 2016 Range Period Covered Range Period Covered Capacity Prices: Eversource, CL&P $ 5.00 — 8.70 per kW-Month 2020 - 2026 $ 5.50 — 8.70 per kW-Month 2020 - 2026 Forward Reserve: Eversource, CL&P $ 1.40 — 2.00 per kW-Month 2017 - 2024 $ 1.40 — 2.00 per kW-Month 2017 - 2024 REC Prices: Eversource, NSTAR Electric $ 27.00 — 30.00 per REC 2017 - 2018 $ 24.00 — 29.00 per REC 2017 - 2018
Rollforward Of Net Derivative Asset Liabilities Valued Using Unobservable Inputs	The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. For the Three Months Ended March 31, 2017 2016 (Millions of Dollars) Eversource CL&P NSTAR Eversource CL&P NSTAR Derivatives, Net: Fair Value as of Beginning of Period $ (423.3 ) $ (420.5 ) $ (2.8 ) $ (380.9 ) $ (380.8 ) $ (0.1 ) Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities (15.4 ) (14.6 ) (0.8 ) (28.9 ) (24.6 ) (4.3 ) Settlements 22.7 21.6 1.1 22.1 20.3 1.8 Fair Value as of End of Period $ (416.0 ) $ (413.5 ) $ (2.5 ) $ (387.7 ) $ (385.1 ) $ (2.6 )

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	3 Months Ended
	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities Reconciliation	The following is a summary of available-for-sale securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of March 31, 2017 As of December 31, 2016 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 $ 296.9 $ 2.4 $ (1.3 ) $ 298.0 $ 296.2 $ 1.1 $ (2.1 ) $ 295.2 Equity Securities 201.9 77.8 (0.5 ) 279.2 203.3 62.3 (1.2 ) 264.4
Investments Classified by Contractual Maturity Date	As of March 31, 2017 , 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) $ 60.6 $ 60.6 One to five years 47.4 48.1 Six to ten years 54.7 55.3 Greater than ten years 134.2 134.0 Total Debt Securities $ 296.9 $ 298.0 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC nuclear decommissioning trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets.
Fair Value on a Recurring Basis	The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of March 31, 2017 As of December 31, 2016 Level 1: Mutual Funds and Equities $ 279.2 $ 274.0 Money Market Funds 56.2 54.8 Total Level 1 $ 335.4 $ 328.8 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 57.0 $ 63.0 Corporate Debt Securities 41.6 41.1 Asset-Backed Debt Securities 19.8 18.5 Municipal Bonds 112.5 107.5 Other Fixed Income Securities 10.9 10.3 Total Level 2 $ 241.8 $ 240.4 Total Marketable Securities $ 577.2 $ 569.2

PENSION BENEFITS AND POSTRETI27

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS (Tables)	3 Months Ended
	Mar. 31, 2017
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit expense for the Pension, SERP and PBOP Plans are shown below. The net periodic benefit expense and the intercompany allocations, less the capitalized portions of pension, SERP and PBOP amounts, are included in Operations and Maintenance expense on the statements of income. Capitalized amounts relate to employees working on capital projects and are included in Property, Plant and Equipment, Net on the balance sheets. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric, PSNH and WMECO does not include the intercompany allocations or the corresponding capitalized portion, as these amounts are cash settled on a short-term basis. Pension and SERP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2017 March 31, 2016 Service Cost $ 18.7 $ 19.4 Interest Cost 46.3 46.5 Expected Return on Pension Plan Assets (83.5 ) (79.6 ) Actuarial Loss 33.6 31.5 Prior Service Cost 1.1 0.9 Total Net Periodic Benefit Expense $ 16.2 $ 18.7 Capitalized Pension Expense $ 5.4 $ 6.1 PBOP Eversource For the Three Months Ended (Millions of Dollars) March 31, 2017 March 31, 2016 Service Cost $ 2.4 $ 3.1 Interest Cost 7.2 9.7 Expected Return on Plan Assets (15.9 ) (15.7 ) Actuarial Loss 2.0 1.1 Prior Service Credit (5.3 ) (0.1 ) Total Net Periodic Benefit Income $ (9.6 ) $ (1.9 ) Capitalized PBOP Income $ (4.6 ) $ (0.9 ) Pension and SERP For the Three Months Ended March 31, 2017 For the Three Months Ended March 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Service Cost $ 4.8 $ 3.3 $ 2.5 $ 0.8 $ 5.0 $ 3.4 $ 2.5 $ 0.9 Interest Cost 10.5 8.3 5.2 2.1 10.6 8.3 5.1 2.1 Expected Return on Pension Plan Assets (18.0 ) (17.6 ) (9.9 ) (4.4 ) (18.2 ) (16.9 ) (9.7 ) (4.4 ) Actuarial Loss 6.9 8.6 2.8 1.5 6.7 8.4 2.5 1.4 Prior Service Cost 0.4 0.1 0.1 0.1 0.4 — 0.1 0.1 Total Net Periodic Benefit Expense $ 4.6 $ 2.7 $ 0.7 $ 0.1 $ 4.5 $ 3.2 $ 0.5 $ 0.1 Intercompany Allocations $ 2.5 $ 1.9 $ 0.8 $ 0.5 $ 3.3 $ 2.2 $ 1.0 $ 0.6 Capitalized Pension Expense $ 2.5 $ 1.7 $ 0.3 $ 0.1 $ 2.7 $ 1.8 $ 0.3 $ 0.2 PBOP For the Three Months Ended March 31, 2017 For the Three Months Ended March 31, 2016 (Millions of Dollars) CL&P NSTAR Electric PSNH WMECO CL&P NSTAR Electric PSNH WMECO Service Cost $ 0.5 $ 0.4 $ 0.3 $ 0.1 $ 0.5 $ 0.9 $ 0.3 $ 0.1 Interest Cost 1.4 2.1 0.8 0.3 1.4 4.0 0.8 0.3 Expected Return on Plan Assets (2.4 ) (6.6 ) (1.3 ) (0.5 ) (2.6 ) (6.4 ) (1.4 ) (0.6 ) Actuarial Loss 0.2 0.9 0.1 — 0.2 0.2 0.1 — Prior Service Cost/(Credit) 0.3 (4.3 ) 0.1 — — — — — Total Net Periodic Benefit Income $ — $ (7.5 ) $ — $ (0.1 ) $ (0.5 ) $ (1.3 ) $ (0.2 ) $ (0.2 ) Intercompany Allocations $ (0.3 ) $ (0.3 ) $ (0.1 ) $ — $ 0.2 $ 0.1 $ — $ — Capitalized PBOP Income $ (0.1 ) $ (3.8 ) $ — $ — $ (0.2 ) $ (0.6 ) $ — $ (0.1 )

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Environmental Loss Contingencies by Site	The number of environmental sites and related reserves for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: As of March 31, 2017 As of December 31, 2016 Number of Sites Reserve (in millions) Number of Sites Reserve (in millions) Eversource 60 $ 58.2 61 $ 65.8 CL&P 14 5.3 14 4.9 NSTAR Electric 13 1.0 13 3.2 PSNH 11 5.3 11 5.3 WMECO 4 0.7 4 0.6
Schedule of Guarantor Obligations	The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries to external parties, as of March 31, 2017 : Company Description Maximum Exposure (in millions) Expiration Dates On behalf of subsidiaries: Eversource Gas Transmission LLC Access Northeast Project Capital Contributions Guaranty $ 185.1 2021 Various Surety Bonds (1) 38.7 2017 - 2018 Eversource Service and Rocky River Realty Company Lease Payments for Vehicles and Real Estate 8.8 2019 - 2024 (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.
Schedule of Complaints and Base ROE	A summary of the four separate complaints and the base ROEs pertinent to those complaints are as follows: Complaint 15-Month Time Period of Complaint (Beginning as of Complaint Filing Date) Original Base ROE Authorized by FERC at Time of Complaint Filing Date (1) Base ROE Subsequently Authorized by FERC for First Complaint Period and also Effective from October 16, 2014 through April 14, 2017 (1) Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions) FERC ALJ Recommendation of Base ROE on Second and Third Complaints (Issued March 22, 2016) First 10/1/2011 - 12/31/2012 11.14% 10.57% $— (2) N/A Second 12/27/2012 - 3/26/2014 11.14% N/A 39.1 (3) 9.59% Third 7/31/2014 - 10/30/2015 11.14% 10.57% — 10.90% Fourth 4/29/2016 - 7/28/2017 10.57% 10.57% — N/A (1) The total ROE between October 1, 2011 and October 15, 2014 was within a range of 11.14 percent to 13.1 percent . In 2014, as a result of a FERC order, the incentive cap was set at 11.74 percent for the first complaint period and also effective from October 16, 2014 through April 14, 2017. (2) CL&P, NSTAR Electric, PSNH and WMECO have refunded all amounts associated with the first complaint period, totaling $38.9 million (pre-tax and excluding interest) at Eversource (including $22.4 million at CL&P, $8.4 million at NSTAR Electric, $2.8 million at PSNH, and $5.3 million at WMECO), reflecting both the base ROE and incentive cap prescribed by the FERC order. (3) The reserve represents the difference between the ROEs billed during the second complaint period and a 10.57 percent base ROE and 11.74 percent incentive cap. The reserve was $21.4 million for CL&P, $8.5 million for NSTAR Electric, $3.1 million for PSNH, and $6.1 million for WMECO as of March 31, 2017.

PSNH GENERATION ASSET SALE - (T

PSNH GENERATION ASSET SALE - (Tables)	3 Months Ended
	Mar. 31, 2017
Regulated Operations [Abstract]
Schedule of Generation Assets and Liabilities	As of March 31, 2017 , PSNH's generation assets were as follows: (Millions of Dollars) Gross Plant $ 1,192.6 Accumulated Depreciation (564.1 ) Net Plant 628.5 Fuel 98.3 Materials and Supplies 48.5 Emission Allowances 19.7 Total Generation Assets $ 795.0

FAIR VALUE OF FINANCIAL INSTR30

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value, by Balance Sheet Grouping	Carrying amounts and estimated fair values are as follows: As of March 31, 2017 As of December 31, 2016 Eversource (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 156.6 $ 155.6 $ 158.3 Long-Term Debt 10,041.8 10,428.0 9,603.2 9,980.5 CL&P NSTAR Electric PSNH WMECO (Millions of Dollars) Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value Carrying Amount Fair Value As of March 31, 2017: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 113.5 $ 43.0 $ 43.1 $ — $ — $ — $ — Long-Term Debt 2,913.2 3,179.5 2,078.5 2,202.9 1,072.3 1,115.2 566.4 596.8 As of December 31, 2016: Preferred Stock Not Subject to Mandatory Redemption $ 116.2 $ 114.7 $ 43.0 $ 43.6 $ — $ — $ — $ — Long-Term Debt 2,766.0 3,049.6 2,078.1 2,201.6 1,072.0 1,109.7 566.5 589.0

ACCUMULATED OTHER COMPREHENSI31

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The changes in accumulated other comprehensive income/(loss) by component, net of tax, is as follows: For the Three Months Ended March 31, 2017 For the Three Months Ended March 31, 2016 Qualified Unrealized Qualified Unrealized Cash Flow Gains Cash Flow Gains/(Losses) Eversource (Millions of Dollars) Hedging on Marketable Defined Hedging on Marketable Defined Instruments Securities Benefit Plans Total Instruments Securities Benefit Plans Total Balance as of Beginning of Period $ (8.2 ) $ 0.4 $ (57.5 ) $ (65.3 ) $ (10.3 ) $ (1.9 ) $ (54.6 ) $ (66.8 ) OCI Before Reclassifications — 1.7 — 1.7 — 0.2 — 0.2 Amounts Reclassified from AOCL 0.5 — 1.0 1.5 0.5 — 0.9 1.4 Net OCI 0.5 1.7 1.0 3.2 0.5 0.2 0.9 1.6 Balance as of End of Period $ (7.7 ) $ 2.1 $ (56.5 ) $ (62.1 ) $ (9.8 ) $ (1.7 ) $ (53.7 ) $ (65.2 )

COMMON SHARES (Tables)

COMMON SHARES (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Schedule of Stock by Class	The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric, PSNH and WMECO that were authorized and issued, as well as the respective per share par values: Shares Authorized as of March 31, 2017 and Issued as of Par Value December 31, 2016 March 31, 2017 December 31, 2016 Eversource $ 5 380,000,000 333,878,402 333,878,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 100 100 PSNH $ 1 100,000,000 301 301 WMECO $ 25 1,072,471 434,653 434,653

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended March 31, 2017 March 31, 2016 Net Income Attributable to Common Shareholders $ 259.5 $ 244.2 Weighted Average Common Shares Outstanding: Basic 317,463,151 317,517,141 Dilutive Effect 661,385 963,909 Diluted 318,124,536 318,481,050 Basic and Diluted EPS $ 0.82 $ 0.77

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Eversource's segment information is as follows: For the Three Months Ended March 31, 2017 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Other Eliminations Total Operating Revenues $ 1,401.1 $ 403.6 $ 316.9 $ 236.3 $ (252.8 ) $ 2,105.1 Depreciation and Amortization (129.8 ) (21.7 ) (50.6 ) (9.2 ) 0.5 (210.8 ) Other Operating Expenses (1,041.9 ) (289.6 ) (90.0 ) (216.6 ) 252.8 (1,385.3 ) Operating Income $ 229.4 $ 92.3 $ 176.3 $ 10.5 $ 0.5 $ 509.0 Interest Expense $ (48.2 ) $ (10.6 ) $ (28.1 ) $ (19.7 ) $ 3.2 $ (103.4 ) Other Income, Net 5.0 0.3 4.9 328.9 (325.5 ) 13.6 Net Income Attributable to Common Shareholders 114.1 50.8 94.2 322.2 (321.8 ) 259.5 Cash Flows Used for Investments in Plant 236.2 64.5 192.6 30.3 — 523.6 For the Three Months Ended March 31, 2016 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Other Eliminations Total Operating Revenues $ 1,436.1 $ 342.6 $ 283.3 $ 214.2 $ (220.6 ) $ 2,055.6 Depreciation and Amortization (127.7 ) (15.8 ) (45.1 ) (6.9 ) 0.5 (195.0 ) Other Operating Expenses (1,088.9 ) (233.5 ) (73.0 ) (197.3 ) 220.6 (1,372.1 ) Operating Income $ 219.5 $ 93.3 $ 165.2 $ 10.0 $ 0.5 $ 488.5 Interest Expense $ (48.0 ) $ (10.1 ) $ (28.0 ) $ (14.1 ) $ 2.0 $ (98.2 ) Other Income/(Loss), Net — (0.3 ) 2.6 305.5 (305.8 ) 2.0 Net Income Attributable to Common Shareholders 108.4 50.9 85.7 302.5 (303.3 ) 244.2 Cash Flows Used for Investments in Plant 184.2 52.1 172.4 22.8 — 431.5 The following table summarizes Eversource's segmented total assets: Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Other Eliminations Total As of March 31, 2017 $ 18,343.3 $ 3,332.7 $ 9,015.6 $ 14,590.4 $ (12,926.8 ) $ 32,355.2 As of December 31, 2016 18,367.5 3,303.8 8,751.5 14,493.1 (12,862.7 ) 32,053.2

SUMMARY OF SIGNIFICANT ACCOUN35

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Basis of Presentation (Details) customer in Millions	3 Months Ended
	Mar. 31, 2017customerutility
Schedule of Equity Method Investments [Line Items]
Number of electric and natural gas customers | customer	3.7
Connecticut, Massachusetts and New Hampshire [Member]
Schedule of Equity Method Investments [Line Items]
Number of regulated utilities | utility	6

SUMMARY OF SIGNIFICANT ACCOUN36

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounting Standards (Details) $ in Millions	Mar. 31, 2017USD ($)
Accounting Policies [Abstract]
Available for sale securities subject to new accounting guidance	$ 49

SUMMARY OF SIGNIFICANT ACCOUN37

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts Narrative (Details)	3 Months Ended
	Mar. 31, 2017
Maximum [Member] | The Connecticut Light And Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of accounts receivable recoverable under financial or medical duress	180 days
Minimum [Member] | Yankee Gas Services Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of accounts receivable recoverable under financial or medical duress	90 days

SUMMARY OF SIGNIFICANT ACCOUN38

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	$ 203.2	$ 200.6
Uncollectible Hardship	118	119.9
The Connecticut Light And Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	88.7	86.4
Uncollectible Hardship	69.8	67.7
NSTAR Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	52.6	54.8
Uncollectible Hardship	23.7	26.2
Public Service Company Of New Hampshire [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	10.4	9.9
Uncollectible Hardship	0	0
Western Massachusetts Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Provision for Uncollectible Accounts	14.2	15.5
Uncollectible Hardship	$ 8.2	$ 9.9

SUMMARY OF SIGNIFICANT ACCOUN39

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Gross Tax Receipts [Line Items]
Excise and sales taxes	$ 42.2	$ 42.2
The Connecticut Light And Power Company [Member]
Schedule of Gross Tax Receipts [Line Items]
Excise and sales taxes	$ 33.9	$ 36

SUMMARY OF SIGNIFICANT ACCOUN40

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Supplemental Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	$ 220.5	$ 125.6
The Connecticut Light And Power Company [Member]
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	104.2	52.6
NSTAR Electric Company [Member]
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	29.8	11.7
Public Service Company Of New Hampshire [Member]
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	28.7	26.8
Western Massachusetts Electric Company [Member]
Schedule of Supplemental Cash Flow [Line Items]
Capital expenditures incurred but not yet paid	$ 19.6	$ 10.7

REGULATORY ACCOUNTING - Compone

REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 4,439,700	$ 4,526,300
Less: Current Portion	875,037	887,625
Total Long-Term Regulatory Assets	3,564,700	3,638,688
Benefit Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	1,782,500	1,817,800
Derivative Liabilities [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	416,300	423,300
Income Taxes, Net [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	645,400	644,500
Storm Restoration Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	375,800	385,300
Goodwill-related [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	459,300	464,400
Regulatory Tracker Mechanisms [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	578,900	576,600
Contractusl Obligations - Yankee Companies [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	70,600	84,900
Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	110,900	129,500
The Connecticut Light And Power Company [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	1,737,600	1,727,100
Less: Current Portion	370,083	335,526
Total Long-Term Regulatory Assets	1,367,486	1,391,564
The Connecticut Light And Power Company [Member] | Benefit Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	421,500	429,300
The Connecticut Light And Power Company [Member] | Derivative Liabilities [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	413,500	420,500
The Connecticut Light And Power Company [Member] | Income Taxes, Net [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	435,900	437,000
The Connecticut Light And Power Company [Member] | Storm Restoration Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	225,100	239,800
The Connecticut Light And Power Company [Member] | Goodwill-related [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
The Connecticut Light And Power Company [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	170,500	123,900
The Connecticut Light And Power Company [Member] | Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	71,100	76,600
NSTAR Electric Company [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	1,327,600	1,347,100
Less: Current Portion	276,476	289,400
Total Long-Term Regulatory Assets	1,051,090	1,057,746
NSTAR Electric Company [Member] | Benefit Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	429,900	438,600
NSTAR Electric Company [Member] | Derivative Liabilities [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	2,500	2,800
NSTAR Electric Company [Member] | Income Taxes, Net [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	90,400	89,700
NSTAR Electric Company [Member] | Storm Restoration Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	118,500	112,500
NSTAR Electric Company [Member] | Goodwill-related [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	394,300	398,700
NSTAR Electric Company [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	245,900	257,300
NSTAR Electric Company [Member] | Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	46,100	47,500
Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	354,900	362,700
Less: Current Portion	111,274	117,240
Total Long-Term Regulatory Assets	243,643	245,525
Public Service Company Of New Hampshire [Member] | Benefit Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	181,100	184,200
Public Service Company Of New Hampshire [Member] | Derivative Liabilities [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
Public Service Company Of New Hampshire [Member] | Income Taxes, Net [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	23,400	24,200
Public Service Company Of New Hampshire [Member] | Storm Restoration Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	17,000	17,100
Public Service Company Of New Hampshire [Member] | Goodwill-related [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
Public Service Company Of New Hampshire [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	101,800	104,500
Public Service Company Of New Hampshire [Member] | Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	31,600	32,700
Western Massachusetts Electric Company [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	189,300	191,400
Less: Current Portion	66,033	64,123
Total Long-Term Regulatory Assets	123,317	127,291
Western Massachusetts Electric Company [Member] | Benefit Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	85,100	86,700
Western Massachusetts Electric Company [Member] | Derivative Liabilities [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
Western Massachusetts Electric Company [Member] | Income Taxes, Net [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	30,900	30,800
Western Massachusetts Electric Company [Member] | Storm Restoration Costs [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	15,200	15,900
Western Massachusetts Electric Company [Member] | Goodwill-related [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
Western Massachusetts Electric Company [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	49,100	46,700
Western Massachusetts Electric Company [Member] | Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 9,000	$ 11,300

REGULATORY ACCOUNTING - Regulat

REGULATORY ACCOUNTING - Regulatory Costs in Other Long-Term Assets (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	$ 91.4	$ 86.3
The Connecticut Light And Power Company [Member]
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	5	5.9
NSTAR Electric Company [Member]
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	33.3	35
Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	12.9	8.2
Western Massachusetts Electric Company [Member]
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	$ 22.1	$ 20.1

REGULATORY ACCOUNTING - Compo43

REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 892,200	$ 849,100
Less: Current Portion	199,160	146,787
Total Long-Term Regulatory Liabilities	692,989	702,255
Cost of Removal [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	469,600	459,700
Benefit Costs [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	130,800	136,200
Regulatory Tracker Mechanisms [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	188,800	145,300
AFUDC - Transmission [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	65,800	65,800
Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	37,200	42,100
The Connecticut Light And Power Company [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	160,100	147,200
Less: Current Portion	58,946	47,055
Total Long-Term Regulatory Liabilities	101,241	100,138
The Connecticut Light And Power Company [Member] | Cost of Removal [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	42,500	38,800
The Connecticut Light And Power Company [Member] | Benefit Costs [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
The Connecticut Light And Power Company [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	44,500	37,200
The Connecticut Light And Power Company [Member] | AFUDC - Transmission [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	49,900	50,200
The Connecticut Light And Power Company [Member] | Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	23,200	21,000
NSTAR Electric Company [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	452,700	455,500
Less: Current Portion	62,154	63,653
Total Long-Term Regulatory Liabilities	390,458	391,823
NSTAR Electric Company [Member] | Cost of Removal [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	273,300	271,600
NSTAR Electric Company [Member] | Benefit Costs [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	109,800	113,100
NSTAR Electric Company [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	62,200	63,700
NSTAR Electric Company [Member] | AFUDC - Transmission [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	7,200	6,900
NSTAR Electric Company [Member] | Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	200	200
Public Service Company Of New Hampshire [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	62,800	57,500
Less: Current Portion	17,224	12,659
Total Long-Term Regulatory Liabilities	45,600	44,779
Public Service Company Of New Hampshire [Member] | Cost of Removal [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	44,800	44,100
Public Service Company Of New Hampshire [Member] | Benefit Costs [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
Public Service Company Of New Hampshire [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	15,000	10,700
Public Service Company Of New Hampshire [Member] | AFUDC - Transmission [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
Public Service Company Of New Hampshire [Member] | Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	3,000	2,700
Western Massachusetts Electric Company [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	32,000	32,100
Less: Current Portion	12,897	14,888
Total Long-Term Regulatory Liabilities	19,119	17,227
Western Massachusetts Electric Company [Member] | Cost of Removal [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	10,600	8,600
Western Massachusetts Electric Company [Member] | Benefit Costs [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
Western Massachusetts Electric Company [Member] | Regulatory Tracker Mechanisms [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	12,700	14,700
Western Massachusetts Electric Company [Member] | AFUDC - Transmission [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	8,700	8,700
Western Massachusetts Electric Company [Member] | Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 0	$ 100

PROPERTY, PLANT AND EQUIPMENT44

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Investment in Utility Property, plant and equipment by asset (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 13,893,900	$ 13,716,900
Distribution - Natural Gas	3,049,300	3,010,400
Transmission	8,600,100	8,517,400
Generation	1,225,600	1,224,200
Electric and Natural Gas Utility	26,768,900	26,468,900
Other	585,100	591,600
Property, Plant and Equipment, Gross	27,354,000	27,060,500
Less: Accumulated Depreciation
Electric and Natural Gas Utility	(6,607,500)	(6,480,400)
Other	(251,300)	(242,000)
Total Accumulated Depreciation	(6,858,800)	(6,722,400)
Property, Plant and Equipment, Net	20,495,200	20,338,100
Construction Work in Progress	1,146,700	1,012,400
Net Plant	21,641,898	21,350,510
The Connecticut Light And Power Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	5,628,700	5,562,900
Transmission	3,930,100	3,912,900
Generation	0	0
Property, Plant and Equipment, Gross	9,558,800	9,475,800
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,125,400)	(2,082,400)
Property, Plant and Equipment, Net	7,433,400	7,393,400
Construction Work in Progress	321,500	239,000
Net Plant	7,754,894	7,632,392
NSTAR Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	5,471,500	5,402,300
Transmission	2,462,800	2,435,800
Generation	0	0
Property, Plant and Equipment, Gross	7,934,300	7,838,100
Less: Accumulated Depreciation
Total Accumulated Depreciation	(2,064,400)	(2,025,400)
Property, Plant and Equipment, Net	5,869,900	5,812,700
Construction Work in Progress	239,000	239,100
Net Plant	6,108,944	6,051,835
Public Service Company Of New Hampshire [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	1,981,900	1,949,800
Transmission	1,075,500	1,059,300
Generation	1,189,600	1,188,200
Property, Plant and Equipment, Gross	4,247,000	4,197,300
Less: Accumulated Depreciation
Total Accumulated Depreciation	(1,277,700)	(1,254,700)
Property, Plant and Equipment, Net	2,969,300	2,942,600
Construction Work in Progress	107,300	96,700
Net Plant	3,076,608	3,039,313
Western Massachusetts Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	851,800	841,900
Transmission	1,083,400	1,061,100
Generation	36,000	36,000
Property, Plant and Equipment, Gross	1,971,200	1,939,000
Less: Accumulated Depreciation
Total Accumulated Depreciation	(347,000)	(338,800)
Property, Plant and Equipment, Net	1,624,200	1,600,200
Construction Work in Progress	70,600	78,100
Net Plant	$ 1,694,818	$ 1,678,262

DERIVATIVE INSTRUMENTS - Gross

DERIVATIVE INSTRUMENTS - Gross Fair Value of Contracts (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Current Derivative Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	$ 0.6	$ 6
Netting	0	0
Net Amount Recorded as a Derivative	0.6	6
Current Derivative Assets [Member] | Eversource and The Connecticut Light And Power Company [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	12.5	13.9
Netting	(8.6)	(9.4)
Net Amount Recorded as a Derivative	3.9	4.5
Long-term Derivative Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	0	0.3
Netting	0	(0.1)
Net Amount Recorded as a Derivative	0	0.2
Long-term Derivative Assets [Member] | Eversource and The Connecticut Light And Power Company [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	78.3	77.3
Netting	(9.8)	(11.7)
Net Amount Recorded as a Derivative	68.5	65.6
Current Derivative Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(72.9)	(79.7)
Netting	0	0
Net Amount Recorded as a Derivative	(72.9)	(79.7)
Current Derivative Liabilities [Member] | The Connecticut Light And Power Company [Member] | Fair Value, Inputs, Level 3 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(70.7)	(77.8)
Netting	0	0
Net Amount Recorded as a Derivative	(70.7)	(77.8)
Current Derivative Liabilities [Member] | NSTAR Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(2.2)	(1.9)
Netting	0	0
Net Amount Recorded as a Derivative	(2.2)	(1.9)
Long-Term Derivative Liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(0.3)	0
Netting	0	0
Net Amount Recorded as a Derivative	(0.3)	0
Long-Term Derivative Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(415.5)	(413.7)
Netting	0	0
Net Amount Recorded as a Derivative	(415.5)	(413.7)
Long-Term Derivative Liabilities [Member] | The Connecticut Light And Power Company [Member] | Fair Value, Inputs, Level 3 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(415.2)	(412.8)
Netting	0	0
Net Amount Recorded as a Derivative	(415.2)	(412.8)
Long-Term Derivative Liabilities [Member] | NSTAR Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(0.3)	(0.9)
Netting	0	0
Net Amount Recorded as a Derivative	$ (0.3)	$ (0.9)

DERIVATIVE INSTRUMENTS - Deriva

DERIVATIVE INSTRUMENTS - Derivative Contracts at Fair Value (Details) MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017USD ($)MMBTUMWhMW	Mar. 31, 2016USD ($)	Dec. 31, 2016MMBTU
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 (up to) | MW	787
Amount of natural gas to be purchased under futures contracts | MMBTU	5.4		9.2
Losses deferred as regulatory costs | $	$ 26.5	$ 30.5
The Connecticut Light And Power Company [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts	80.00%
Amount of energy to be purchased under renewable energy contract (in mwh) | MWh	0.1
NSTAR Electric Company [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of power to be purchased under capacity-related contract (up to) | MW	35
Amount of energy to be purchased under renewable energy contract (in mwh) | MWh	0.1

DERIVATIVE INSTRUMENTS - Unobse

DERIVATIVE INSTRUMENTS - Unobservable Inputs Utilized (Details) - Fair Value, Inputs, Level 3 [Member] - $ / KWmo	Mar. 31, 2017	Dec. 31, 2016
Eversource and The Connecticut Light And Power Company [Member] | Minimum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Capacity Prices (in USDPerKiloWattMonth)	5	5.50
Forward Reserve (in USDPerKiloWattMonth)	1.40	1.40
Eversource and The Connecticut Light And Power Company [Member] | Maximum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Capacity Prices (in USDPerKiloWattMonth)	8.70	8.70
Forward Reserve (in USDPerKiloWattMonth)	2	2
Eversource and NSTAR Electric Company [Member] | Minimum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
REC Prices (in USDPerKiloWattMonth)	27	24
Eversource and NSTAR Electric Company [Member] | Maximum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
REC Prices (in USDPerKiloWattMonth)	30	29

DERIVATIVE INSTRUMENTS - Unob48

DERIVATIVE INSTRUMENTS - Unobservable Inputs Narrative (Details) - Fair Value, Inputs, Level 3 [Member]	3 Months Ended
	Mar. 31, 2017
Minimum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	2.00%
Maximum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts	19.00%

DERIVATIVE INSTRUMENTS - Deri49

DERIVATIVE INSTRUMENTS - Derivative Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	$ (423.3)	$ (380.9)
Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities	(15.4)	(28.9)
Settlements	22.7	22.1
Fair Value as of End of Period	(416)	(387.7)
The Connecticut Light And Power Company [Member]
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	(420.5)	(380.8)
Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities	(14.6)	(24.6)
Settlements	21.6	20.3
Fair Value as of End of Period	(413.5)	(385.1)
NSTAR Electric Company [Member]
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	(2.8)	(0.1)
Net Realized/Unrealized Losses Included in Regulatory Assets and Liabilities	(0.8)	(4.3)
Settlements	1.1	1.8
Fair Value as of End of Period	$ (2.5)	$ (2.6)

MARKETABLE SECURITIES - Trading

MARKETABLE SECURITIES - Trading Securities (Details) - Fair Value, Inputs, Level 1 [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of securities under fair value option		$ 9.6
Other Income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net gain (loss) under fair value option	$ 0.2

MARKETABLE SECURITIES - Schedul

MARKETABLE SECURITIES - Schedule of Available for Sale Securities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 296.9	$ 296.2
Pre-Tax Unrealized Gains	2.4	1.1
Pre-Tax Unrealized Losses	(1.3)	(2.1)
Fair Value	298	295.2
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	201.9	203.3
Pre-Tax Unrealized Gains	77.8	62.3
Pre-Tax Unrealized Losses	(0.5)	(1.2)
Fair Value	$ 279.2	$ 264.4

MARKETABLE SECURITIES - Availab

MARKETABLE SECURITIES - Available for Sale Securities Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Debt, equity and marketable securities held in nuclear decommissioning trust	$ 482.3	$ 466.7

MARKETABLE SECURITIES - Sched53

MARKETABLE SECURITIES - Schedule of Contractual Maturities (Details) $ in Millions	Mar. 31, 2017USD ($)
Amortized Cost
Less than one year	$ 60.6
One to five years	47.4
Six to ten years	54.7
Greater than ten years	134.2
Total Debt Securities	296.9
Fair Value
Less than one year	60.6
One to five years	48.1
Six to ten years	55.3
Greater than ten years	134
Total Debt Securities	$ 298

MARKETABLE SECURITIES - Sched54

MARKETABLE SECURITIES - Schedule of Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	$ 577.2	$ 569.2
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	335.4	328.8
Fair Value, Inputs, Level 1 [Member] | Mutual Funds and Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	279.2	274
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	56.2	54.8
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	241.8	240.4
Fair Value, Inputs, Level 2 [Member] | U.S. Government Issued Debt Securities (Agency and Treasury) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	57	63
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	41.6	41.1
Fair Value, Inputs, Level 2 [Member] | Asset-Backed Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	19.8	18.5
Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	112.5	107.5
Fair Value, Inputs, Level 2 [Member] | Other Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities recorded at fair value on a recurring basis	$ 10.9	$ 10.3

SHORT-TERM AND LONG-TERM DEBT -

SHORT-TERM AND LONG-TERM DEBT - Commercial Paper Programs and Credit Agreements (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Eversource Parent [Member]
Line of Credit Facility [Line Items]
Amount outstanding during period	$ 0	$ 0
Eversource Parent [Member] | Commercial Paper [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	1,450,000,000
Short-term borrowings outstanding	801,000,000	1,000,000,000
Remaining borrowing capacity	$ 649,000,000	$ 428,000,000
Weighted average interest rate (as a percentage)	1.12%	0.88%
Eversource Parent [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,450,000,000
Debt instrument term	5 years
The Connecticut Light And Power Company [Member]
Line of Credit Facility [Line Items]
Notes payable to Eversource Parent	$ 3,400,000	$ 80,100,000
Public Service Company Of New Hampshire [Member]
Line of Credit Facility [Line Items]
Notes payable to Eversource Parent	144,900,000	160,900,000
Western Massachusetts Electric Company [Member]
Line of Credit Facility [Line Items]
Notes payable to Eversource Parent	71,400,000	51,000,000
NSTAR Electric Company [Member]
Line of Credit Facility [Line Items]
Amount outstanding during period	0	0
NSTAR Electric Company [Member] | Commercial Paper [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	450,000,000
Short-term borrowings outstanding	174,500,000	126,500,000
Remaining borrowing capacity	$ 275,500,000	$ 323,500,000
Weighted average interest rate (as a percentage)	0.86%	0.71%
NSTAR Electric Company [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 450,000,000
Debt instrument term	5 years

SHORT-TERM AND LONG-TERM DEBT56

SHORT-TERM AND LONG-TERM DEBT - Long-Term Debt Issuances (Details) - Senior Notes [Member]	Mar. 31, 2017USD ($)
Eversource Parent [Member] | Series K Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 300,000,000
Interest rate stated percentage	2.75%
The Connecticut Light And Power Company [Member] | 2017 Series A First and Refunding Mortgage Bonds Due 2027 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 300,000,000
Interest rate stated percentage	3.20%

SHORT-TERM AND LONG-TERM DEBT57

SHORT-TERM AND LONG-TERM DEBT - Long-Term Debt Repayments (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2017	Mar. 31, 2016
Debt Instrument [Line Items]
Repayments of debt		$ 150,000	$ 0
The Connecticut Light And Power Company [Member]
Debt Instrument [Line Items]
Repayments of debt		$ 150,000	$ 0
2007 Series A First and Refunding Mortgage Bonds [Member] | Senior Notes [Member] | The Connecticut Light And Power Company [Member]
Debt Instrument [Line Items]
Repayments of debt	$ 150,000
Interest rate stated percentage	5.375%	5.375%

SHORT-TERM AND LONG - Long-Term

SHORT-TERM AND LONG - Long-Term Debt Issuance Authorization (Details) - Senior Notes [Member] - USD ($) $ in Millions	Mar. 30, 2017	Jan. 04, 2017
The Connecticut Light And Power Company [Member]
Debt Instrument [Line Items]
Amount of debt authorized (up to)		$ 1,325
NSTAR Electric Company [Member]
Debt Instrument [Line Items]
Amount of debt authorized (up to)	$ 700

PENSION BENEFITS AND POSTRETI59

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Pension Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Prior service credit as a result of remeasurement	$ 5.3

PENSION BENEFITS AND POSTRETI60

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS - Components of Periodic Benefit Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 18.7	$ 19.4
Interest Cost	46.3	46.5
Expected Return on Pension Plan Assets	(83.5)	(79.6)
Actuarial Loss	33.6	31.5
Prior Service Cost/(Credit)	1.1	0.9
Total Net Periodic Benefit Income	16.2	18.7
Capitalized PBOP Income	5.4	6.1
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.4	3.1
Interest Cost	7.2	9.7
Expected Return on Pension Plan Assets	(15.9)	(15.7)
Actuarial Loss	2	1.1
Prior Service Cost/(Credit)	(5.3)	(0.1)
Total Net Periodic Benefit Income	(9.6)	(1.9)
Capitalized PBOP Income	(4.6)	(0.9)
The Connecticut Light And Power Company [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	4.8	5
Interest Cost	10.5	10.6
Expected Return on Pension Plan Assets	(18)	(18.2)
Actuarial Loss	6.9	6.7
Prior Service Cost/(Credit)	0.4	0.4
Total Net Periodic Benefit Income	4.6	4.5
Intercompany Allocations	2.5	3.3
Capitalized PBOP Income	2.5	2.7
The Connecticut Light And Power Company [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.5	0.5
Interest Cost	1.4	1.4
Expected Return on Pension Plan Assets	(2.4)	(2.6)
Actuarial Loss	0.2	0.2
Prior Service Cost/(Credit)	0.3	0
Total Net Periodic Benefit Income	0	(0.5)
Intercompany Allocations	(0.3)	0.2
Capitalized PBOP Income	(0.1)	(0.2)
NSTAR Electric Company [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	3.3	3.4
Interest Cost	8.3	8.3
Expected Return on Pension Plan Assets	(17.6)	(16.9)
Actuarial Loss	8.6	8.4
Prior Service Cost/(Credit)	0.1	0
Total Net Periodic Benefit Income	2.7	3.2
Intercompany Allocations	1.9	2.2
Capitalized PBOP Income	1.7	1.8
NSTAR Electric Company [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.4	0.9
Interest Cost	2.1	4
Expected Return on Pension Plan Assets	(6.6)	(6.4)
Actuarial Loss	0.9	0.2
Prior Service Cost/(Credit)	(4.3)	0
Total Net Periodic Benefit Income	(7.5)	(1.3)
Intercompany Allocations	(0.3)	0.1
Capitalized PBOP Income	(3.8)	(0.6)
Public Service Company Of New Hampshire [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.5	2.5
Interest Cost	5.2	5.1
Expected Return on Pension Plan Assets	(9.9)	(9.7)
Actuarial Loss	2.8	2.5
Prior Service Cost/(Credit)	0.1	0.1
Total Net Periodic Benefit Income	0.7	0.5
Intercompany Allocations	0.8	1
Capitalized PBOP Income	0.3	0.3
Public Service Company Of New Hampshire [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.3	0.3
Interest Cost	0.8	0.8
Expected Return on Pension Plan Assets	(1.3)	(1.4)
Actuarial Loss	0.1	0.1
Prior Service Cost/(Credit)	0.1	0
Total Net Periodic Benefit Income	0	(0.2)
Intercompany Allocations	(0.1)	0
Capitalized PBOP Income	0	0
Western Massachusetts Electric Company [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.8	0.9
Interest Cost	2.1	2.1
Expected Return on Pension Plan Assets	(4.4)	(4.4)
Actuarial Loss	1.5	1.4
Prior Service Cost/(Credit)	0.1	0.1
Total Net Periodic Benefit Income	0.1	0.1
Intercompany Allocations	0.5	0.6
Capitalized PBOP Income	0.1	0.2
Western Massachusetts Electric Company [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.1	0.1
Interest Cost	0.3	0.3
Expected Return on Pension Plan Assets	(0.5)	(0.6)
Actuarial Loss	0	0
Prior Service Cost/(Credit)	0	0
Total Net Periodic Benefit Income	(0.1)	(0.2)
Intercompany Allocations	0	0
Capitalized PBOP Income	$ 0	$ (0.1)

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Schedule of Environmental Matters (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)site	Dec. 31, 2016USD ($)site
Site Contingency [Line Items]
Number of Sites | site	60	61
Reserve | $	$ 58.2	$ 65.8
The Connecticut Light And Power Company [Member]
Site Contingency [Line Items]
Number of Sites | site	14	14
Reserve | $	$ 5.3	$ 4.9
NSTAR Electric Company [Member]
Site Contingency [Line Items]
Number of Sites | site	13	13
Reserve | $	$ 1	$ 3.2
Public Service Company Of New Hampshire [Member]
Site Contingency [Line Items]
Number of Sites | site	11	11
Reserve | $	$ 5.3	$ 5.3
Western Massachusetts Electric Company [Member]
Site Contingency [Line Items]
Number of Sites | site	4	4
Reserve | $	$ 0.7	$ 0.6

COMMITMENTS AND CONTINGENCIES62

COMMITMENTS AND CONTINGENCIES - Environmental Matters Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Site Contingency [Line Items]
Reserve	$ 58.2	$ 65.8
MGP Site accrual [Member]
Site Contingency [Line Items]
Reserve	$ 53	$ 59

COMMITMENTS AND CONTINGENCIES63

COMMITMENTS AND CONTINGENCIES - Guarantees and Indemnifications Narrative (Details) $ in Millions	Mar. 31, 2017USD ($)
Access Northeast [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure (up to)	$ 206
Guarantee Of Financial Obligations Of Npt [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure (up to)	25
Guarantee Of Npt Letters Of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure (up to)	$ 14

COMMITMENTS AND CONTINGENCIES64

COMMITMENTS AND CONTINGENCIES - Schedule of Guarantees and Indemnifications (Details) $ in Millions	Mar. 31, 2017USD ($)
Access Northeast Project Capital Contributions Guarantee Expiring In 2021 [Member]
Loss Contingencies [Line Items]
Maximum Exposure	$ 185.1
Various Subsidiary Surety Bonds And Performance Guarantees Expiring Between 2016 And 2018 [Member]
Loss Contingencies [Line Items]
Maximum Exposure	38.7
Guarantee Of Rocky River Reality And Nusco Lease Payments For Real Estate And Vehicles Expiring 2019 Through 2024 [Member]
Loss Contingencies [Line Items]
Maximum Exposure	$ 8.8

COMMITMENTS AND CONTINGENCIES65

COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) - USD ($) $ in Millions	Apr. 14, 2017	Apr. 29, 2016	Mar. 31, 2017	Mar. 26, 2014
FERC ROE First, Second and Third Complaints [Member]
Loss Contingencies [Line Items]
Base ROE percentage challenged by complainants			11.14%
FERC ROE Complaints [Member]
Loss Contingencies [Line Items]
Period of complaint			15 months
Basis point change			10.00%
Estimate of possible loss for each 10 basis point change to base ROE			$ 3
FERC ROE Fourth Complaint [Member]
Loss Contingencies [Line Items]
Base ROE percentage of complaint period		10.57%
Maximum percentage cap of ROE for incentive projects		11.74%
Loss contingency, estimate of possible earnings impact			0
FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			0
FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Base ROE percentage of complaint period				10.57%
Loss contingency, estimate of possible earnings impact			39.1
The Connecticut Light And Power Company [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			21.4
NSTAR Electric Company [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			8.5
Public Service Company Of New Hampshire [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			3.1
Western Massachusetts Electric Company [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			$ 6.1
Subsequent Event [Member] | FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Base ROE percentage challenged by complainants	11.14%

COMMITMENTS AND CONTINGENCIES66

COMMITMENTS AND CONTINGENCIES - Schedule of Complaints and Base ROEs (Details) - USD ($) $ in Millions	3 Months Ended	15 Months Ended			16 Months Ended	30 Months Ended	36 Months Ended
	Mar. 31, 2017	Jul. 30, 2017	Mar. 26, 2014	Dec. 31, 2012	Oct. 30, 2015	Mar. 31, 2017	Oct. 15, 2014
FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)				11.14%
Base ROE Subsequently Authorized by FERC for first complaint period and prospectively from October 16, 2014 (in percentage)				10.57%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	$ 0					$ 0
Percentage of maximum ROE for any incentive project						11.74%
Customer Refund Payments	38.9
FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)			11.14%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	39.1					$ 39.1
FERC ALJ Recommendation of base ROE on Second and Third Complaints (Issued March 22, 2016) (in percentage)			9.59%
Percentage of maximum ROE for any incentive project			11.74%
FERC ROE Third Complaint [Member]
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)					11.14%
Base ROE Subsequently Authorized by FERC for first complaint period and prospectively from October 16, 2014 (in percentage)					10.57%
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	0					0
FERC ALJ Recommendation of base ROE on Second and Third Complaints (Issued March 22, 2016) (in percentage)					10.90%
FERC ROE Fourth Complaint [Member]
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	0					0
Scenario, Forecast [Member] | FERC ROE Fourth Complaint [Member]
Loss Contingencies [Line Items]
Original Base ROE Authorized by FERC at Time of Complaint (in percentage)		10.57%
Base ROE Subsequently Authorized by FERC for first complaint period and prospectively from October 16, 2014 (in percentage)		10.57%
The Connecticut Light And Power Company [Member] | FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Customer Refund Payments	22.4
The Connecticut Light And Power Company [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	21.4					21.4
NSTAR Electric Company [Member] | FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Customer Refund Payments	8.4
NSTAR Electric Company [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	8.5					8.5
Public Service Company Of New Hampshire [Member] | FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Customer Refund Payments	2.8
Public Service Company Of New Hampshire [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	3.1					3.1
Western Massachusetts Electric Company [Member] | FERC ROE First Complaint [Member]
Loss Contingencies [Line Items]
Customer Refund Payments	5.3
Western Massachusetts Electric Company [Member] | FERC ROE Second Complaint [Member]
Loss Contingencies [Line Items]
Reserve (Pre-Tax and Excluding Interest) as of March 31, 2017 (in millions)	$ 6.1					$ 6.1
Minimum [Member] | FERC ROE First, Second and Third Complaints [Member]
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project							11.14%
Maximum [Member] | FERC ROE First, Second and Third Complaints [Member]
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project							13.10%

PSNH GENERATION ASSET SALE - Na

PSNH GENERATION ASSET SALE - Narrative (Details) $ in Thousands	Jun. 10, 2015USD ($)senator	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Regulatory Assets [Line Items]
Equity return related to clean air project forgone	$ 25,000
Other current liabilities		$ 639,366	$ 684,914
Accrued Pension and SERP		1,077,593	1,141,514
Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Other current liabilities		52,771	43,253
Accrued Pension and SERP		91,911	$ 94,652
Electricity Generation Plant, Non-Nuclear [Member] | Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Number of state senators | senator	2
Payments for restructuring	$ 5,000
Accounts payable		30,100
Other current liabilities		21,700
Asset retirement obligation		20,300
Accrued Pension and SERP		$ 23,700

PSNH GENERATION ASSET SALE - PS

PSNH GENERATION ASSET SALE - PSNH Generation Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Regulatory Assets [Line Items]
Gross Plant	$ 27,354,000	$ 27,060,500
Accumulated Depreciation	(6,858,800)	(6,722,400)
Net Plant	21,641,898	21,350,510
Emission Allowances	361,779	328,721
Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Gross Plant	4,247,000	4,197,300
Accumulated Depreciation	(1,277,700)	(1,254,700)
Net Plant	3,076,608	3,039,313
Emission Allowances	165,725	$ 162,354
Electricity Generation Plant, Non-Nuclear [Member] | Public Service Company Of New Hampshire [Member]
Regulatory Assets [Line Items]
Gross Plant	1,192,600
Accumulated Depreciation	(564,100)
Net Plant	628,500
Fuel	98,300
Materials and Supplies	48,500
Emission Allowances	19,700
Total Generation Assets	$ 795,000

FAIR VALUE OF FINANCIAL INSTR69

FAIR VALUE OF FINANCIAL INSTRUMENTS - Carrying Amounts and Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	$ 155,568	$ 155,568
Carrying Amount | Fair Value, Inputs, Level 2 [Member]
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	10,041,800	9,603,200
Fair Value | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	156,600	158,300
Long-Term Debt	10,428,000	9,980,500
The Connecticut Light And Power Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
The Connecticut Light And Power Company [Member] | Carrying Amount | Fair Value, Inputs, Level 2 [Member]
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	2,913,200	2,766,000
The Connecticut Light And Power Company [Member] | Fair Value | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	113,500	114,700
Long-Term Debt	3,179,500	3,049,600
NSTAR Electric Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
NSTAR Electric Company [Member] | Carrying Amount | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
Long-Term Debt	2,078,500	2,078,100
NSTAR Electric Company [Member] | Fair Value | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,100	43,600
Long-Term Debt	2,202,900	2,201,600
Public Service Company Of New Hampshire [Member] | Carrying Amount | Fair Value, Inputs, Level 2 [Member]
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	1,072,300	1,072,000
Public Service Company Of New Hampshire [Member] | Fair Value | Fair Value, Inputs, Level 2 [Member]
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	1,115,200	1,109,700
Western Massachusetts Electric Company [Member] | Carrying Amount | Fair Value, Inputs, Level 2 [Member]
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	566,400	566,500
Western Massachusetts Electric Company [Member] | Fair Value | Fair Value, Inputs, Level 2 [Member]
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	$ 596,800	$ 589,000

ACCUMULATED OTHER COMPREHENSI70

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Accumulated Other Comprehensive Income (loss) by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent [Roll Forward]
Balance as of Beginning of Period	$ (65,282)
OCI Before Reclassifications	1,700	$ 200
Amounts Reclassified from AOCL	1,500	1,400
Net OCI	3,141	1,669
Balance as of End of Period	(62,141)
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Balance as of Beginning of Period	(65,300)	(66,800)
Balance as of End of Period	(62,100)	(65,200)
Qualified Cash Flow Hedging Instruments [Member]
AOCI Attributable to Parent [Roll Forward]
Balance as of Beginning of Period	(8,200)	(10,300)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCL	500	500
Net OCI	500	500
Balance as of End of Period	(7,700)	(9,800)
Unrealized Gains/(Losses) on Marketable Securities [Member]
AOCI Attributable to Parent [Roll Forward]
Balance as of Beginning of Period	400	(1,900)
OCI Before Reclassifications	1,700	200
Amounts Reclassified from AOCL	0	0
Net OCI	1,700	200
Balance as of End of Period	2,100	(1,700)
Defined Benefit Plans [Member]
AOCI Attributable to Parent [Roll Forward]
Balance as of Beginning of Period	(57,500)	(54,600)
OCI Before Reclassifications	0	0
Amounts Reclassified from AOCL	1,000	900
Net OCI	1,000	900
Balance as of End of Period	$ (56,500)	$ (53,700)

COMMON SHARES - Schedule of Com

COMMON SHARES - Schedule of Common Shares (Details) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 5	$ 5
Authorized (in shares)	380,000,000	380,000,000
Issued (in shares)	333,878,402	333,878,402
The Connecticut Light And Power Company [Member]
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 10	$ 10
Authorized (in shares)	24,500,000	24,500,000
Issued (in shares)	6,035,205	6,035,205
NSTAR Electric Company [Member]
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 1	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	100	100
Public Service Company Of New Hampshire [Member]
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 1	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	301	301
Western Massachusetts Electric Company [Member]
Class of Stock [Line Items]
Per Value (in dollars per share)	$ 25	$ 25
Authorized (in shares)	1,072,471	1,072,471
Issued (in shares)	434,653	434,653

COMMON SHARES - Narrative (Deta

COMMON SHARES - Narrative (Details) - shares	Mar. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Treasury stock (in shares)	16,992,594	16,992,594
Common stock outstanding (in shares)	316,885,808	316,885,808

COMMON SHAREHOLDERS' EQUITY A73

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Class of Stock [Line Items]
Noncontrolling Interest - Preferred Stock of Subsidiaries	$ 155,568		$ 155,568
The Connecticut Light And Power Company [Member]
Class of Stock [Line Items]
Net income attributable to noncontrolling interests	1,900
Noncontrolling Interest - Preferred Stock of Subsidiaries	116,200		116,200
NSTAR Electric Company [Member]
Class of Stock [Line Items]
Net income attributable to noncontrolling interests		$ 1,900
Noncontrolling Interest - Preferred Stock of Subsidiaries	$ 43,000		$ 43,000

EARNINGS PER SHARE - Narrative

EARNINGS PER SHARE - Narrative (Details) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Antidilutive share awards excluded from computation (in shares)	0	0

EARNINGS PER SHARE - Schedule o

EARNINGS PER SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 259,458	$ 244,153
Weighted Average Common Shares Outstanding:
Basic (in shares)	317,463,151	317,517,141
Dilutive Effect (in shares)	661,385	963,909
Diluted (in shares)	318,124,536	318,481,050
Basic and Diluted EPS (in dollars per share)	$ 0.82	$ 0.77

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)companiessegment
Segment Reporting Information [Line Items]
Number of companies that transmit hydro electricity imported from The Hydro-Quebec System in Canada | companies	2
Amount of natural gas transmission purchased from Enbridge by Yankee Gas and NSTAR Gas | $	$ 62.5
The Connecticut Light And Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
NSTAR Electric Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Public Service Company Of New Hampshire [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Western Massachusetts Electric Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1

SEGMENT INFORMATION - Schedule

SEGMENT INFORMATION - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,105,135	$ 2,055,635
Depreciation and Amortization	(210,800)	(195,000)
Other Operating Expenses	(1,385,300)	(1,372,100)
Operating Income/(Loss)	509,019	488,536
Interest Expense	(103,429)	(98,212)
Other Income/(Loss), Net	13,577	2,011
Net Income Attributable to Common Shareholders	259,458	244,153
Cash Flows Used for Investments in Plant	523,560	431,472
Assets	32,355,176		$ 32,053,173
Operating Segments [Member] | Electric Distribution [Member]
Segment Reporting Information [Line Items]
Operating Revenues	1,401,100	1,436,100
Depreciation and Amortization	(129,800)	(127,700)
Other Operating Expenses	(1,041,900)	(1,088,900)
Operating Income/(Loss)	229,400	219,500
Interest Expense	(48,200)	(48,000)
Other Income/(Loss), Net	5,000	0
Net Income Attributable to Common Shareholders	114,100	108,400
Cash Flows Used for Investments in Plant	236,200	184,200
Assets	18,343,300		18,367,500
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Operating Revenues	403,600	342,600
Depreciation and Amortization	(21,700)	(15,800)
Other Operating Expenses	(289,600)	(233,500)
Operating Income/(Loss)	92,300	93,300
Interest Expense	(10,600)	(10,100)
Other Income/(Loss), Net	300	(300)
Net Income Attributable to Common Shareholders	50,800	50,900
Cash Flows Used for Investments in Plant	64,500	52,100
Assets	3,332,700		3,303,800
Operating Segments [Member] | Electric Transmission [Member]
Segment Reporting Information [Line Items]
Operating Revenues	316,900	283,300
Depreciation and Amortization	(50,600)	(45,100)
Other Operating Expenses	(90,000)	(73,000)
Operating Income/(Loss)	176,300	165,200
Interest Expense	(28,100)	(28,000)
Other Income/(Loss), Net	4,900	2,600
Net Income Attributable to Common Shareholders	94,200	85,700
Cash Flows Used for Investments in Plant	192,600	172,400
Assets	9,015,600		8,751,500
Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Operating Revenues	236,300	214,200
Depreciation and Amortization	(9,200)	(6,900)
Other Operating Expenses	(216,600)	(197,300)
Operating Income/(Loss)	10,500	10,000
Interest Expense	(19,700)	(14,100)
Other Income/(Loss), Net	328,900	305,500
Net Income Attributable to Common Shareholders	322,200	302,500
Cash Flows Used for Investments in Plant	30,300	22,800
Assets	14,590,400		14,493,100
Eliminations [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(252,800)	(220,600)
Depreciation and Amortization	500	500
Other Operating Expenses	252,800	220,600
Operating Income/(Loss)	500	500
Interest Expense	3,200	2,000
Other Income/(Loss), Net	(325,500)	(305,800)
Net Income Attributable to Common Shareholders	(321,800)	(303,300)
Cash Flows Used for Investments in Plant	0	$ 0
Assets	$ (12,926,800)		$ (12,862,700)