CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current Assets:
Cash and Cash Equivalents	$ 24,638	$ 30,251
Receivables, Net	833,945	847,301
Unbilled Revenues	158,183	168,490
Fuel, Materials, Supplies and Inventory	286,296	328,721
Regulatory Assets	870,393	887,625
Prepayments and Other Current Assets	157,359	215,284
Total Current Assets	2,330,814	2,477,672
Property, Plant and Equipment, Net	22,071,496	21,350,510
Deferred Debits and Other Assets:
Regulatory Assets	3,580,981	3,638,688
Goodwill	3,519,401	3,519,401
Marketable Securities	565,460	544,642
Other Long-Term Assets	590,688	522,260
Total Deferred Debits and Other Assets	8,256,530	8,224,991
Total Assets	32,658,840	32,053,173
Current Liabilities:
Notes Payable	937,500	1,148,500
Long-Term Debt – Current Portion	1,483,883	773,883
Accounts Payable	587,174	884,521
Regulatory Liabilities	185,930	146,787
Other Current Liabilities	591,222	684,914
Total Current Liabilities	3,785,709	3,638,605
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	5,900,052	5,607,207
Regulatory Liabilities	696,740	702,255
Derivative Liabilities	402,138	413,676
Accrued Pension and SERP	1,073,510	1,141,514
Other Long-Term Liabilities	860,579	853,260
Total Deferred Credits and Other Liabilities	8,933,019	8,717,912
Capitalization:
Long-Term Debt	8,899,021	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	6,232,501	6,250,224
Retained Earnings	3,364,336	3,175,171
Accumulated Other Comprehensive Loss	(62,935)	(65,282)
Treasury Stock	(317,771)	(317,771)
Common Stockholder's Equity	10,885,523	10,711,734
Total Capitalization	19,940,112	19,696,656
Total Liabilities and Capitalization	32,658,840	32,053,173
The Connecticut Light And Power Company [Member]
Current Assets:
Cash and Cash Equivalents	5,837	6,579
Receivables, Net	371,504	359,132
Accounts Receivable from Affiliated Companies	22,805	16,851
Unbilled Revenues	50,436	50,373
Materials, Supplies and Inventory	57,324	52,050
Regulatory Assets	346,520	335,526
Prepayments and Other Current Assets	14,608	52,670
Total Current Assets	869,034	873,181
Property, Plant and Equipment, Net	7,940,398	7,632,392
Deferred Debits and Other Assets:
Regulatory Assets	1,343,011	1,391,564
Other Long-Term Assets	138,405	137,907
Total Deferred Debits and Other Assets	1,481,416	1,529,471
Total Assets	10,290,848	10,035,044
Current Liabilities:
Notes Payable to Eversource Parent	101,100	80,100
Long-Term Debt – Current Portion	400,000	250,000
Accounts Payable	229,435	289,532
Accounts Payable to Affiliated Companies	54,046	88,075
Obligations to Third Party Suppliers	52,854	55,520
Regulatory Liabilities	62,195	47,055
Derivative Liabilities	64,301	77,765
Other Current Liabilities	143,998	120,399
Total Current Liabilities	1,107,929	1,008,446
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	2,071,421	1,987,661
Regulatory Liabilities	101,863	100,138
Derivative Liabilities	402,002	412,750
Accrued Pension and SERP	301,691	300,208
Other Long-Term Liabilities	125,996	123,244
Total Deferred Credits and Other Liabilities	3,002,973	2,924,001
Capitalization:
Long-Term Debt	2,513,522	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	2,110,739	2,110,714
Retained Earnings	1,378,895	1,299,374
Accumulated Other Comprehensive Loss	238	(53)
Common Stockholder's Equity	3,550,224	3,470,387
Total Capitalization	6,179,946	6,102,597
Total Liabilities and Capitalization	10,290,848	10,035,044
NSTAR Electric Company [Member]
Current Assets:
Cash and Cash Equivalents	4,475	3,494
Receivables, Net	261,344	257,557
Accounts Receivable from Affiliated Companies	28,619	8,581
Unbilled Revenues	40,163	31,632
Taxes Receivable	3,532	39,738
Fuel, Materials, Supplies and Inventory	35,067	62,288
Regulatory Assets	270,230	289,400
Prepayments and Other Current Assets	17,730	14,906
Total Current Assets	661,160	707,596
Property, Plant and Equipment, Net	6,188,535	6,051,835
Deferred Debits and Other Assets:
Regulatory Assets	1,064,099	1,057,746
Prepaid PBOP	109,658	95,073
Other Long-Term Assets	71,657	60,572
Total Deferred Debits and Other Assets	1,245,414	1,213,391
Total Assets	8,095,109	7,972,822
Current Liabilities:
Notes Payable	0	126,500
Long-Term Debt – Current Portion	400,000	400,000
Accounts Payable	151,056	232,599
Accounts Payable to Affiliated Companies	8,389	91,532
Obligations to Third Party Suppliers	67,254	55,863
Renewable Portfolio Standards Compliance Obligations	44,258	75,571
Regulatory Liabilities	48,350	63,653
Other Current Liabilities	48,736	71,122
Total Current Liabilities	768,043	1,116,840
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,898,526	1,836,292
Regulatory Liabilities	394,527	391,823
Accrued Pension and SERP	111,994	111,827
Other Long-Term Liabilities	130,023	123,194
Total Deferred Credits and Other Liabilities	2,535,070	2,463,136
Capitalization:
Long-Term Debt	2,025,929	1,678,116
Noncontrolling Interest - Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,047,178	1,045,378
Retained Earnings	1,675,529	1,625,984
Accumulated Other Comprehensive Loss	360	368
Common Stockholder's Equity	2,723,067	2,671,730
Total Capitalization	4,791,996	4,392,846
Total Liabilities and Capitalization	8,095,109	7,972,822
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash and Cash Equivalents	192	4,646
Receivables, Net	81,937	84,450
Accounts Receivable from Affiliated Companies	3,781	4,185
Unbilled Revenues	41,723	41,004
Taxes Receivable	27,122	6,177
Fuel, Materials, Supplies and Inventory	150,066	162,354
Regulatory Assets	132,424	117,240
Prepayments and Other Current Assets	20,514	22,731
Total Current Assets	457,759	442,787
Property, Plant and Equipment, Net	3,118,456	3,039,313
Deferred Debits and Other Assets:
Regulatory Assets	249,612	245,525
Other Long-Term Assets	47,075	37,720
Total Deferred Debits and Other Assets	296,687	283,245
Total Assets	3,872,902	3,765,345
Current Liabilities:
Notes Payable to Eversource Parent	194,100	160,900
Long-Term Debt – Current Portion	180,000	70,000
Accounts Payable	78,218	85,716
Accounts Payable to Affiliated Companies	21,207	29,154
Regulatory Liabilities	13,696	12,659
Other Current Liabilities	46,415	43,253
Total Current Liabilities	533,636	401,682
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	821,799	785,385
Regulatory Liabilities	43,845	44,779
Accrued Pension and SERP	101,143	94,652
Other Long-Term Liabilities	50,051	49,442
Total Deferred Credits and Other Liabilities	1,016,838	974,258
Capitalization:
Long-Term Debt	892,333	1,002,048
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	843,134	843,134
Retained Earnings	591,288	549,286
Accumulated Other Comprehensive Loss	(4,327)	(5,063)
Common Stockholder's Equity	1,430,095	1,387,357
Total Capitalization	2,322,428	2,389,405
Total Liabilities and Capitalization	3,872,902	3,765,345
Western Massachusetts Electric Company [Member]
Current Assets:
Cash and Cash Equivalents	0	0
Receivables, Net	54,178	54,940
Accounts Receivable from Affiliated Companies	11,393	14,425
Unbilled Revenues	17,335	15,329
Fuel, Materials, Supplies and Inventory	5,784	8,618
Regulatory Assets	67,310	64,123
Prepayments and Other Current Assets	1,821	2,595
Total Current Assets	157,821	160,030
Property, Plant and Equipment, Net	1,719,824	1,678,262
Deferred Debits and Other Assets:
Regulatory Assets	124,899	127,291
Other Long-Term Assets	33,780	29,062
Total Deferred Debits and Other Assets	158,679	156,353
Total Assets	2,036,324	1,994,645
Current Liabilities:
Notes Payable to Eversource Parent	68,700	51,000
Accounts Payable	32,258	56,036
Accounts Payable to Affiliated Companies	28,484	19,478
Obligations to Third Party Suppliers	9,458	10,508
Renewable Portfolio Standards Compliance Obligations	11,114	20,383
Regulatory Liabilities	11,062	14,888
Other Current Liabilities	12,574	14,984
Total Current Liabilities	173,650	187,277
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	523,028	490,793
Regulatory Liabilities	20,887	17,227
Accrued Pension and SERP	19,798	20,390
Other Long-Term Liabilities	45,471	41,308
Total Deferred Credits and Other Liabilities	609,184	569,718
Capitalization:
Long-Term Debt	566,293	566,536
Common Shareholders' Equity:
Common Shares	10,866	10,866
Capital Surplus, Paid In	444,398	444,398
Retained Earnings	234,051	218,212
Accumulated Other Comprehensive Loss	(2,118)	(2,362)
Common Stockholder's Equity	687,197	671,114
Total Capitalization	1,253,490	1,237,650
Total Liabilities and Capitalization	$ 2,036,324	$ 1,994,645