CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Current Assets:
Cash	$ 41,706	$ 43,364
Receivables, Net	848,510	765,391
Unbilled Revenues	181,284	224,982
Fuel, Materials and Supplies	333,869	303,233
Regulatory Assets Current	445,962	535,791
Marketable Securities - Current	114,722	92,427
Prepayments and Other Current Assets	135,497	121,861
Total Current Assets	2,101,550	2,087,049
Property, Plant and Equipment, Net	18,254,610	17,576,186
Deferred Debits and Other Assets:
Regulatory Assets Long Term	3,241,122	3,758,694
Goodwill	3,519,401	3,519,401
Marketable Securities	518,032	488,515
Other Long-Term Assets	347,596	365,692
Total Deferred Debits and Other Assets	7,626,151	8,132,302
Total Assets	27,982,311	27,795,537
Current Liabilities:
Notes Payable	1,046,961	1,093,000
Long-Term Debt - Current Portion	245,583	533,346
Accounts Payable - Current	608,639	742,251
Regulatory Liability Current	398,985	204,278
Other Liabilities - Current	629,508	702,776
Total Current Liabilities	2,929,676	3,275,651
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	4,257,996	4,029,026
Regulatory Liabilities Long-Term	509,889	502,984
Long-Term Derivative Liabilities	420,931	624,050
Accrued Pension, PBOP and SERP	787,550	896,844
Other Long-Term Liabilities	863,164	923,053
Total Deferred Credits and Other Liabilities	6,839,530	6,975,957
Capitalization:
Long-Term Debt	8,166,985	7,776,833
Noncontrolling Interest in Consolidated Subsidiary:
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	155,568	155,568
Common Shareholders' Equity:
Common Stock	1,666,767	1,665,351
Capital Surplus, Paid In	6,219,516	6,192,765
Retained Earnings	2,351,421	2,125,980
Accumulated Other Comprehensive Loss	(40,172)	(46,031)
Treasury Stock	(306,980)	(326,537)
Common Shareholders' Equity	9,890,552	9,611,528
Total Capitalization	18,213,105	17,543,929
Total Liabilities and Capitalization	27,982,311	27,795,537
The Connecticut Light And Power Company [Member]
Current Assets:
Cash	16,294	7,237
Receivables, Net	369,492	319,670
Accounts Receivable from Affiliated Companies	35,276	13,777
Unbilled Revenues	87,806	92,401
Regulatory Assets Current	116,531	150,943
Materials and Supplies	47,086	54,606
Accumulated Deferred Income Tax Asset	52,839
Prepaid Taxes	47,429	13,962
Prepayments and Other Current Assets	17,608	39,120
Total Current Assets	790,361	691,716
Property, Plant and Equipment, Net	6,700,798	6,451,259
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,369,025	1,663,147
Other Long-Term Assets	178,313	174,380
Total Deferred Debits and Other Assets	1,547,338	1,837,527
Total Assets	9,038,497	8,980,502
Current Liabilities:
Notes Payable To Affiliated Companies	105,400	287,300
Long-Term Debt - Current Portion	162,000	150,000
Accounts Payable - Current	228,379	201,047
Accounts Payable to Affiliated Companies	46,977	56,531
Obligations to Third Party Suppliers	67,630	73,914
Accrued Taxes	54,652	37,186
Regulatory Liability Current	195,663	93,961
Derivative Liabilities - Current	86,759	92,233
Other Liabilities - Current	107,284	97,530
Total Current Liabilities	1,054,744	1,089,702
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,581,344	1,510,586
Regulatory Liabilities Long-Term	87,696	93,757
Long-Term Derivative Liabilities	418,137	617,072
Accrued Pension, PBOP and SERP	63,756	95,895
Other Long-Term Liabilities	143,838	163,588
Total Deferred Credits and Other Liabilities	2,294,771	2,480,898
Capitalization:
Long-Term Debt	2,679,775	2,591,208
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	1,804,228	1,682,047
Retained Earnings	1,029,473	961,482
Accumulated Other Comprehensive Loss	(1,046)	(1,387)
Common Shareholders' Equity	2,893,007	2,702,494
Total Capitalization	5,688,982	5,409,902
Total Liabilities and Capitalization	9,038,497	8,980,502
NSTAR Electric Company [Member]
Current Assets:
Cash	11,040	8,021
Receivables, Net	275,902	209,711
Accounts Receivable from Affiliated Companies	47,215	27,264
Unbilled Revenues	39,372	41,368
Fuel, Materials and Supplies	65,073	44,236
Regulatory Assets Current	128,205	204,144
Prepayments and Other Current Assets	11,267	36,710
Total Current Assets	578,074	571,454
Property, Plant and Equipment, Net	5,211,681	5,043,887
Deferred Debits and Other Assets:
Regulatory Assets Long Term	998,030	1,235,156
Other Long-Term Assets	62,644	60,624
Total Deferred Debits and Other Assets	1,060,674	1,295,780
Total Assets	6,850,429	6,911,121
Current Liabilities:
Notes Payable	159,500	103,500
Long-Term Debt - Current Portion	4,700	301,650
Accounts Payable - Current	128,056	202,100
Accounts Payable to Affiliated Companies	62,625	75,707
Obligations to Third Party Suppliers	37,298
Power Contract Obligation	35,783	30,842
Renewable Portfolio Standards Compliance Obligation	34,905	39,686
Accrued Taxes	42,338	7,946
Deferred Tax Liabilities Current	9,622	50,128
Regulatory Liability Current	97,215	53,958
Other Liabilities - Current	62,436	39,936
Total Current Liabilities	674,478	910,912
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,425,306	1,466,835
Regulatory Liabilities Long-Term	266,524	253,108
Accrued Pension, PBOP and SERP	142,249	118,010
Other Long-Term Liabilities	112,853	142,214
Due To Related Parties Noncurrent	0	64,172
Total Deferred Credits and Other Liabilities	1,946,932	2,044,339
Capitalization:
Long-Term Debt	1,792,707	1,499,417
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	993,163	992,625
Retained Earnings	1,400,149	1,420,828
Common Shareholders' Equity	2,393,312	2,413,453
Total Capitalization	4,229,019	3,955,870
Total Liabilities and Capitalization	6,850,429	6,911,121
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash	2,750	130
Receivables, Net	77,602	76,331
Accounts Receivable from Affiliated Companies	6,271	90
Unbilled Revenues	33,088	38,344
Fuel, Materials and Supplies	141,381	128,736
Regulatory Assets Current	102,473	92,194
Prepayments and Other Current Assets	22,270	24,100
Total Current Assets	385,835	359,925
Property, Plant and Equipment, Net	2,560,635	2,467,556
Deferred Debits and Other Assets:
Regulatory Assets Long Term	178,204	219,346
Other Long-Term Assets	54,748	39,891
Total Deferred Debits and Other Assets	232,952	259,237
Total Assets	3,179,422	3,086,718
Current Liabilities:
Notes Payable To Affiliated Companies	153,300	86,500
Long-Term Debt - Current Portion	0	50,000
Accounts Payable - Current	58,801	82,920
Accounts Payable to Affiliated Companies	22,932	22,040
Deferred Tax Liabilities Current	29,936	28,596
Regulatory Liability Current	29,165	20,643
Other Liabilities - Current	38,725	51,729
Total Current Liabilities	332,859	342,428
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	566,298	500,166
Regulatory Liabilities Long-Term	50,614	51,723
Other Postretirement Benefit Plan Liability	14,320	15,272
Other Long-Term Liabilities	46,874	46,247
Total Deferred Credits and Other Liabilities	678,106	613,408
Capitalization:
Long-Term Debt	999,230	999,006
Common Shareholders' Equity:
Common Stock	0	0
Capital Surplus, Paid In	702,923	701,911
Retained Earnings	473,969	438,515
Accumulated Other Comprehensive Loss	(7,665)	(8,550)
Common Shareholders' Equity	1,169,227	1,131,876
Total Capitalization	2,168,457	2,130,882
Total Liabilities and Capitalization	3,179,422	3,086,718
Western Massachusetts Electric Company [Member]
Current Assets:
Cash	1,737	0
Receivables, Net	50,835	49,018
Accounts Receivable from Affiliated Companies	14,522	47,607
Unbilled Revenues	12,664	16,562
Taxes Receivable	11,504	432
Regulatory Assets Current	38,907	43,024
Marketable Securities - Current	22,107	26,628
Prepayments and Other Current Assets	6,688	10,479
Total Current Assets	158,964	193,750
Property, Plant and Equipment, Net	1,432,368	1,381,060
Deferred Debits and Other Assets:
Regulatory Assets Long Term	109,690	146,088
Marketable Securities	35,963	31,243
Other Long-Term Assets	50,902	40,679
Total Deferred Debits and Other Assets	196,555	218,010
Total Assets	1,787,887	1,792,820
Current Liabilities:
Notes Payable To Affiliated Companies	13,200	0
Long-Term Debt - Current Portion	50,000
Accounts Payable - Current	36,558	62,961
Accounts Payable to Affiliated Companies	13,312	9,230
Accrued Interest	2,839	7,525
Deferred Tax Liabilities Current	1,920	13,098
Regulatory Liability Current	43,462	19,858
Counterparty Deposit	626	7,688
Other Liabilities - Current	11,758	20,629
Total Current Liabilities	173,675	140,989
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	413,701	396,933
Regulatory Liabilities Long-Term	10,289	13,873
Other Postretirement Benefit Plan Liability	2,623	3,911
Other Long-Term Liabilities	38,372	28,619
Total Deferred Credits and Other Liabilities	464,985	443,336
Capitalization:
Long-Term Debt	578,686	629,389
Common Shareholders' Equity:
Common Stock	10,866	10,866
Capital Surplus, Paid In	391,136	390,743
Retained Earnings	171,800	181,014
Accumulated Other Comprehensive Loss	(3,261)	(3,517)
Common Shareholders' Equity	570,541	579,106
Total Capitalization	1,149,227	1,208,495
Total Liabilities and Capitalization	$ 1,787,887	$ 1,792,820