CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and Cash Equivalents	$ 30,251	$ 23,947
Receivables, Net	847,301	775,480
Unbilled Revenues	168,490	202,647
Taxes Receivable	80,471	305,359
Fuel, Materials, Supplies and Inventory	328,721	336,476
Regulatory Assets	887,625	845,843
Prepayments and Other Current Assets	134,813	129,034
Total Current Assets	2,477,672	2,618,786
Property, Plant and Equipment, Net	21,350,510	19,892,441
Deferred Debits and Other Assets:
Regulatory Assets	3,638,688	3,737,960
Goodwill	3,519,401	3,519,401
Marketable Securities	544,642	516,478
Other Long-Term Assets	522,260	295,243
Total Deferred Debits and Other Assets	8,224,991	8,069,082
Total Assets	32,053,173	30,580,309
Current Liabilities:
Notes Payable	1,148,500	1,160,953
Long-Term Debt – Current Portion	773,883	228,883
Accounts Payable	884,521	813,646
Regulatory Liabilities	146,787	107,759
Other Current Liabilities	684,914	678,549
Total Current Liabilities	3,638,605	2,989,790
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	5,607,207	5,147,678
Regulatory Liabilities	702,255	513,595
Derivative Liabilities	413,676	337,102
Accrued Pension, SERP and PBOP	1,141,514	1,407,288
Other Long-Term Liabilities	853,260	871,499
Total Deferred Credits and Other Liabilities	8,717,912	8,277,162
Capitalization:
Long-Term Debt	8,829,354	8,805,574
Noncontrolling Interest - Preferred Stock of Subsidiaries	155,568	155,568
Common Shareholders' Equity:
Common Shares	1,669,392	1,669,313
Capital Surplus, Paid In	6,250,224	6,262,368
Retained Earnings	3,175,171	2,797,355
Accumulated Other Comprehensive Loss	(65,282)	(66,844)
Treasury Stock	(317,771)	(309,977)
Common Shareholders' Equity	10,711,734	10,352,215
Total Capitalization	19,696,656	19,313,357
Commitments and Contingencies (Note 11)
Total Liabilities and Capitalization	32,053,173	30,580,309
The Connecticut Light And Power Company [Member]
Current Assets:
Cash and Cash Equivalents	6,579	1,057
Receivables, Net	359,132	352,536
Accounts Receivable from Affiliated Companies	16,851	21,214
Unbilled Revenues	50,373	99,879
Taxes Receivable	19,700	137,643
Materials, Supplies and Inventory	52,050	43,124
Regulatory Assets	335,526	268,318
Prepayments and Other Current Assets	32,970	32,234
Total Current Assets	873,181	956,005
Property, Plant and Equipment, Net	7,632,392	7,156,809
Deferred Debits and Other Assets:
Regulatory Assets	1,391,564	1,369,028
Other Long-Term Assets	137,907	111,115
Total Deferred Debits and Other Assets	1,529,471	1,480,143
Total Assets	10,035,044	9,592,957
Current Liabilities:
Notes Payable to Eversource Parent	80,100	277,400
Long-Term Debt – Current Portion	250,000	0
Accounts Payable	289,532	267,764
Accounts Payable to Affiliated Companies	88,075	66,456
Obligations to Third Party Suppliers	55,520	60,746
Regulatory Liabilities	47,055	61,155
Derivative Liabilities	77,765	91,820
Other Current Liabilities	120,399	110,631
Total Current Liabilities	1,008,446	935,972
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,987,661	1,820,865
Regulatory Liabilities	100,138	74,830
Derivative Liabilities	412,750	336,189
Accrued Pension, SERP and PBOP	300,208	271,056
Other Long-Term Liabilities	123,244	133,446
Total Deferred Credits and Other Liabilities	2,924,001	2,636,386
Capitalization:
Long-Term Debt	2,516,010	2,763,682
Noncontrolling Interest - Preferred Stock of Subsidiaries	116,200	116,200
Common Shareholders' Equity:
Common Shares	60,352	60,352
Capital Surplus, Paid In	2,110,714	1,910,663
Retained Earnings	1,299,374	1,170,278
Accumulated Other Comprehensive Loss	(53)	(576)
Common Shareholders' Equity	3,470,387	3,140,717
Total Capitalization	6,102,597	6,020,599
Commitments and Contingencies (Note 11)
Total Liabilities and Capitalization	10,035,044	9,592,957
NSTAR Electric Company [Member]
Current Assets:
Cash and Cash Equivalents	3,494	3,346
Receivables, Net	257,557	229,936
Accounts Receivable from Affiliated Companies	8,581	4,034
Unbilled Revenues	31,632	29,464
Taxes Receivable	39,738	70,236
Materials, Supplies and Inventory	62,288	75,487
Regulatory Assets	289,400	348,408
Prepayments and Other Current Assets	14,906	11,448
Total Current Assets	707,596	772,359
Property, Plant and Equipment, Net	6,051,835	5,655,458
Deferred Debits and Other Assets:
Regulatory Assets	1,057,746	1,112,977
Prepaid PBOP	95,073	0
Other Long-Term Assets	60,572	62,467
Total Deferred Debits and Other Assets	1,213,391	1,175,444
Total Assets	7,972,822	7,603,261
Current Liabilities:
Notes Payable	126,500	62,500
Long-Term Debt – Current Portion	400,000	200,000
Accounts Payable	232,599	228,250
Accounts Payable to Affiliated Companies	91,532	38,648
Obligations to Third Party Suppliers	55,863	56,718
Renewable Portfolio Standards Compliance Obligations	75,571	104,847
Regulatory Liabilities	63,653	3,281
Other Current Liabilities	71,122	72,007
Total Current Liabilities	1,116,840	766,251
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,836,292	1,760,339
Regulatory Liabilities	391,823	264,352
Accrued Pension, SERP and PBOP	111,827	209,153
Other Long-Term Liabilities	123,194	120,939
Total Deferred Credits and Other Liabilities	2,463,136	2,354,783
Capitalization:
Long-Term Debt	1,678,116	1,829,766
Noncontrolling Interest - Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,045,378	995,378
Retained Earnings	1,625,984	1,613,538
Accumulated Other Comprehensive Loss	368	545
Common Shareholders' Equity	2,671,730	2,609,461
Total Capitalization	4,392,846	4,482,227
Commitments and Contingencies (Note 11)
Total Liabilities and Capitalization	7,972,822	7,603,261
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash and Cash Equivalents	4,646	1,733
Receivables, Net	84,450	77,546
Accounts Receivable from Affiliated Companies	4,185	2,352
Unbilled Revenues	41,004	38,207
Taxes Receivable	6,177	43,128
Fuel, Materials, Supplies and Inventory	162,354	156,868
Regulatory Assets	117,240	104,971
Prepayments and Other Current Assets	22,731	24,302
Total Current Assets	442,787	449,107
Property, Plant and Equipment, Net	3,039,313	2,855,363
Deferred Debits and Other Assets:
Regulatory Assets	245,525	257,873
Other Long-Term Assets	37,720	34,176
Total Deferred Debits and Other Assets	283,245	292,049
Total Assets	3,765,345	3,596,519
Current Liabilities:
Notes Payable to Eversource Parent	160,900	231,300
Long-Term Debt – Current Portion	70,000	0
Accounts Payable	85,716	87,925
Accounts Payable to Affiliated Companies	29,154	24,214
Regulatory Liabilities	12,659	6,898
Other Current Liabilities	43,253	43,921
Total Current Liabilities	401,682	394,258
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	785,385	705,894
Regulatory Liabilities	44,779	47,851
Accrued Pension, SERP and PBOP	94,652	89,579
Other Long-Term Liabilities	49,442	50,746
Total Deferred Credits and Other Liabilities	974,258	894,070
Capitalization:
Long-Term Debt	1,002,048	1,071,017
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	843,134	748,634
Retained Earnings	549,286	494,901
Accumulated Other Comprehensive Loss	(5,063)	(6,361)
Common Shareholders' Equity	1,387,357	1,237,174
Total Capitalization	2,389,405	2,308,191
Commitments and Contingencies (Note 11)
Total Liabilities and Capitalization	3,765,345	3,596,519
Western Massachusetts Electric Company [Member]
Current Assets:
Cash and Cash Equivalents	0	834
Receivables, Net	54,940	50,912
Accounts Receivable from Affiliated Companies	14,425	18,633
Unbilled Revenues	15,329	15,065
Taxes Receivable	1,067	33,407
Materials, Supplies and Inventory	8,618	5,992
Regulatory Assets	64,123	56,166
Prepayments and Other Current Assets	1,528	1,890
Total Current Assets	160,030	182,899
Property, Plant and Equipment, Net	1,678,262	1,575,306
Deferred Debits and Other Assets:
Regulatory Assets	127,291	135,010
Other Long-Term Assets	29,062	24,875
Total Deferred Debits and Other Assets	156,353	159,885
Total Assets	1,994,645	1,918,090
Current Liabilities:
Notes Payable to Eversource Parent	51,000	143,400
Accounts Payable	56,036	58,364
Accounts Payable to Affiliated Companies	19,478	19,896
Obligations to Third Party Suppliers	10,508	9,654
Renewable Portfolio Standards Compliance Obligations	20,383	6,395
Regulatory Liabilities	14,888	13,122
Other Current Liabilities	14,984	13,878
Total Current Liabilities	187,277	264,709
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	490,793	470,539
Regulatory Liabilities	17,227	11,597
Accrued Pension, SERP and PBOP	20,390	19,515
Other Long-Term Liabilities	41,308	36,819
Total Deferred Credits and Other Liabilities	569,718	538,470
Capitalization:
Long-Term Debt	566,536	517,329
Common Shareholders' Equity:
Common Shares	10,866	10,866
Capital Surplus, Paid In	444,398	391,398
Retained Earnings	218,212	198,140
Accumulated Other Comprehensive Loss	(2,362)	(2,822)
Common Shareholders' Equity	671,114	597,582
Total Capitalization	1,237,650	1,114,911
Commitments and Contingencies (Note 11)
Total Liabilities and Capitalization	$ 1,994,645	$ 1,918,090