CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash	$ 23,947	$ 38,703
Receivables, Net	775,480	856,346
Unbilled Revenues	202,647	211,758
Taxes Receivable	305,359	337,307
Fuel, Materials and Supplies	336,476	349,664
Regulatory Assets Current	845,843	672,493
Prepayments and Other Current Assets	129,034	226,194
Total Current Assets	2,618,786	2,692,465
Property, Plant and Equipment, Net	19,892,441	18,647,041
Deferred Debits and Other Assets:
Regulatory Assets Long Term	3,737,960	4,054,086
Goodwill	3,519,401	3,519,401
Marketable Securities	516,478	515,025
Other Long-Term Assets	295,243	312,369
Total Deferred Debits and Other Assets	8,069,082	8,400,881
Total Assets	30,580,309	29,740,387
Current Liabilities:
Notes Payable	1,160,953	956,825
Long-Term Debt - Current Portion	228,883	245,583
Accounts Payable - Current	813,646	868,231
Regulatory Liability Current	107,759	235,022
Deferred Tax Liabilities Current		160,288
Other Liabilities - Current	678,549	668,432
Total Current Liabilities	2,989,790	3,134,381
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	5,147,678	4,467,473
Regulatory Liabilities Long-Term	513,595	515,144
Long-Term Derivative Liabilities	337,102	409,632
Accrued Pension, SERP and PBOP	1,407,288	1,638,558
Other Long-Term Liabilities	871,499	874,387
Total Deferred Credits and Other Liabilities	8,277,162	7,905,194
Capitalization:
Long-Term Debt	8,805,574	8,568,429
Noncontrolling Interest in Consolidated Subsidiary:
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	155,568	155,568
Common Shareholders' Equity:
Common Stock	1,669,313	1,666,796
Capital Surplus, Paid In	6,262,368	6,235,834
Retained Earnings	2,797,355	2,448,661
Accumulated Other Comprehensive Loss	(66,844)	(74,009)
Treasury Stock	(309,977)	(300,467)
Common Shareholders' Equity	10,352,215	9,976,815
Total Capitalization	19,313,357	18,700,812
Total Liabilities and Capitalization	30,580,309	29,740,387
The Connecticut Light And Power Company [Member]
Current Assets:
Cash	1,057	2,356
Receivables, Net	352,536	355,140
Accounts Receivable from Affiliated Companies	21,214	16,757
Unbilled Revenues	99,879	102,137
Taxes Receivable	137,643	116,148
Regulatory Assets Current	268,318	220,344
Materials and Supplies	43,124	46,664
Prepayments and Other Current Assets	32,234	37,822
Total Current Assets	956,005	897,368
Property, Plant and Equipment, Net	7,156,809	6,809,664
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,369,028	1,475,508
Other Long-Term Assets	111,115	161,860
Total Deferred Debits and Other Assets	1,480,143	1,637,368
Total Assets	9,592,957	9,344,400
Current Liabilities:
Notes Payable To Affiliated Companies	277,400	133,400
Long-Term Debt - Current Portion	0	162,000
Accounts Payable - Current	267,764	272,971
Accounts Payable to Affiliated Companies	66,456	65,594
Obligations to Third Party Suppliers	60,746	73,624
Regulatory Liability Current	61,155	124,722
Deferred Tax Liabilities Current		34,100
Derivative Liabilities - Current	91,820	88,459
Other Liabilities - Current	110,631	153,420
Total Current Liabilities	935,972	1,074,190
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,820,865	1,642,805
Regulatory Liabilities Long-Term	74,830	81,298
Long-Term Derivative Liabilities	336,189	406,199
Accrued Pension, SERP and PBOP	271,056	273,854
Other Long-Term Liabilities	133,446	148,844
Total Deferred Credits and Other Liabilities	2,636,386	2,553,000
Capitalization:
Long-Term Debt	2,763,682	2,664,243
Noncontrolling Interest in Consolidated Subsidiary:
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	116,200	116,200
Common Shareholders' Equity:
Common Stock	60,352	60,352
Capital Surplus, Paid In	1,910,663	1,804,869
Retained Earnings	1,170,278	1,072,477
Accumulated Other Comprehensive Loss	(576)	(931)
Common Shareholders' Equity	3,140,717	2,936,767
Total Capitalization	6,020,599	5,717,210
Total Liabilities and Capitalization	9,592,957	9,344,400
NSTAR Electric Company [Member]
Current Assets:
Cash	3,346	12,773
Receivables, Net	229,936	234,481
Accounts Receivable from Affiliated Companies	4,034	40,353
Unbilled Revenues	29,464	29,741
Taxes Receivable	70,236	144,601
Regulatory Assets Current	348,408	198,710
Materials and Supplies	75,487	74,179
Prepayments and Other Current Assets	11,448	10,815
Total Current Assets	772,359	745,653
Property, Plant and Equipment, Net	5,655,458	5,335,436
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,112,977	1,179,100
Other Long-Term Assets	62,467	61,880
Total Deferred Debits and Other Assets	1,175,444	1,240,980
Total Assets	7,603,261	7,322,069
Current Liabilities:
Notes Payable	62,500	302,000
Long-Term Debt - Current Portion	200,000	4,700
Accounts Payable - Current	228,250	217,311
Accounts Payable to Affiliated Companies	38,648	63,517
Obligations to Third Party Suppliers	56,718	34,824
Renewable Portfolio Standards Compliance Obligation	104,847	60,750
Regulatory Liability Current	3,281	49,611
Deferred Tax Liabilities Current	0	55,136
Other Liabilities - Current	72,007	90,939
Total Current Liabilities	766,251	878,788
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,760,339	1,527,667
Regulatory Liabilities Long-Term	264,352	262,738
Accrued Pension, SERP and PBOP	209,153	235,529
Other Long-Term Liabilities	120,939	129,279
Total Deferred Credits and Other Liabilities	2,354,783	2,155,213
Capitalization:
Long-Term Debt	1,829,766	1,781,541
Noncontrolling Interest in Consolidated Subsidiary:
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	43,000	43,000
Common Shareholders' Equity:
Common Stock	0	0
Capital Surplus, Paid In	995,378	994,130
Retained Earnings	1,613,538	1,468,955
Accumulated Other Comprehensive Loss	545	442
Common Shareholders' Equity	2,609,461	2,463,527
Total Capitalization	4,482,227	4,288,068
Total Liabilities and Capitalization	7,603,261	7,322,069
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash	1,733	489
Receivables, Net	77,546	80,151
Accounts Receivable from Affiliated Companies	2,352	3,194
Unbilled Revenues	38,207	40,181
Taxes Receivable	43,128	14,571
Fuel, Materials and Supplies	156,868	148,139
Regulatory Assets Current	104,971	111,705
Prepayments and Other Current Assets	24,302	27,821
Total Current Assets	449,107	426,251
Property, Plant and Equipment, Net	2,855,363	2,635,844
Deferred Debits and Other Assets:
Regulatory Assets Long Term	257,873	293,115
Other Long-Term Assets	34,176	32,963
Total Deferred Debits and Other Assets	292,049	326,078
Total Assets	3,596,519	3,388,173
Current Liabilities:
Notes Payable To Affiliated Companies	231,300	90,500
Accounts Payable - Current	87,925	93,349
Accounts Payable to Affiliated Companies	24,214	33,734
Regulatory Liability Current	6,898	16,044
Deferred Tax Liabilities Current	0	36,164
Other Liabilities - Current	43,921	38,969
Total Current Liabilities	394,258	308,760
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	705,894	587,292
Regulatory Liabilities Long-Term	47,851	51,372
Accrued Pension, SERP and PBOP	89,579	93,243
Other Long-Term Liabilities	50,746	50,155
Total Deferred Credits and Other Liabilities	894,070	782,062
Capitalization:
Long-Term Debt	1,071,017	1,070,021
Common Shareholders' Equity:
Common Stock	0	0
Capital Surplus, Paid In	748,634	748,240
Retained Earnings	494,901	486,459
Accumulated Other Comprehensive Loss	(6,361)	(7,369)
Common Shareholders' Equity	1,237,174	1,227,330
Total Capitalization	2,308,191	2,297,351
Total Liabilities and Capitalization	3,596,519	3,388,173
Western Massachusetts Electric Company [Member]
Current Assets:
Cash	834
Receivables, Net	50,912	51,066
Accounts Receivable from Affiliated Companies	18,633	7,851
Unbilled Revenues	15,065	15,146
Taxes Receivable	33,407	18,126
Regulatory Assets Current	56,166	51,923
Marketable Securities - Current	0	28,658
Prepayments and Other Current Assets	7,882	7,607
Total Current Assets	182,899	180,377
Property, Plant and Equipment, Net	1,575,306	1,461,321
Deferred Debits and Other Assets:
Regulatory Assets Long Term	135,010	146,307
Marketable Securities	0	29,452
Other Long-Term Assets	24,875	18,731
Total Deferred Debits and Other Assets	159,885	194,490
Total Assets	1,918,090	1,836,188
Current Liabilities:
Notes Payable To Affiliated Companies	143,400	21,400
Long-Term Debt - Current Portion	0	50,000
Accounts Payable - Current	58,364	53,732
Accounts Payable to Affiliated Companies	19,896	14,328
Regulatory Liability Current	13,122	22,486
Deferred Tax Liabilities Current	0	18,089
Other Liabilities - Current	29,927	24,080
Total Current Liabilities	264,709	204,115
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	470,539	416,822
Regulatory Liabilities Long-Term	11,597	10,835
Other Postretirement Benefit Plan Liability		17,705
Accrued Pension, SERP and PBOP	19,515
Other Long-Term Liabilities	36,819	33,747
Total Deferred Credits and Other Liabilities	538,470	479,109
Capitalization:
Long-Term Debt	517,329	575,184
Common Shareholders' Equity:
Common Stock	10,866	10,866
Capital Surplus, Paid In	391,398	391,256
Retained Earnings	198,140	178,834
Accumulated Other Comprehensive Loss	(2,822)	(3,176)
Common Shareholders' Equity	597,582	577,780
Total Capitalization	1,114,911	1,152,964
Total Liabilities and Capitalization	1,918,090	1,836,188
Eversource Parent [Member]
Current Assets:
Cash	67	138
Accounts Receivable from Affiliated Companies	23,689	6,725
Notes Receivable from Affiliated Companies	850,300	741,150
Prepayments and Other Current Assets	41,254	41,366
Total Current Assets	915,310	789,379
Deferred Debits and Other Assets:
Equity Method Investments	8,915,178	8,387,976
Notes Receivable, Related Parties, Noncurrent	128,800	106,300
Deferred Tax Assets, Net, Noncurrent	143,054	177,908
Goodwill	3,231,811	3,231,811
Other Long-Term Assets	48,314	34,483
Total Deferred Debits and Other Assets	12,467,157	11,938,478
Total Assets	13,382,467	12,727,857
Current Liabilities:
Notes Payable	1,098,453	654,825
Long-Term Debt - Current Portion	28,883	28,883
Accounts Payable - Current	78	141
Accounts Payable to Affiliated Companies	15,601	150,268
Other Liabilities - Current	60,999	71,778
Total Current Liabilities	1,204,014	905,895
Deferred Credits and Other Liabilities:
Other Long-Term Liabilities	134,908	125,608
Total Deferred Credits and Other Liabilities	134,908	125,608
Capitalization:
Long-Term Debt	1,691,330	1,719,539
Common Shareholders' Equity:
Common Stock	1,669,313	1,666,796
Capital Surplus, Paid In	6,262,368	6,235,834
Retained Earnings	2,797,355	2,448,661
Accumulated Other Comprehensive Loss	(66,844)	(74,009)
Treasury Stock	(309,977)	(300,467)
Common Shareholders' Equity	10,352,215	9,976,815
Total Capitalization	12,043,545	11,696,354
Total Liabilities and Capitalization	$ 13,382,467	$ 12,727,857