CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current Assets:
Cash	$ 34,096	$ 43,364
Receivables, Net	807,510	765,391
Unbilled Revenues	193,983	224,982
Fuel, Materials and Supplies	281,721	303,233
Regulatory Assets Current	467,156	535,791
Marketable Securities - Current	115,987	92,427
Prepayments and Other Current Assets	168,022	121,861
Total Current Assets	2,068,475	2,087,049
Property, Plant and Equipment, Net	17,978,692	17,576,186
Deferred Debits and Other Assets:
Regulatory Assets Long Term	3,339,457	3,758,694
Goodwill	3,519,401	3,519,401
Marketable Securities	513,986	488,515
Other Long-Term Assets	370,434	365,692
Total Deferred Debits and Other Assets	7,743,278	8,132,302
Total Assets	27,790,445	27,795,537
Current Liabilities:
Notes Payable to Banks	905,000	1,093,000
Long-Term Debt - Current Portion	395,583	533,346
Accounts Payable - Current	561,699	742,251
Regulatory Liability Current	359,921	204,278
Other Liabilities - Current	580,605	702,776
Total Current Liabilities	2,802,808	3,275,651
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	4,270,050	4,029,026
Regulatory Liabilities Long-Term	503,955	502,984
Long-Term Derivative Liabilities	449,439	624,050
Accrued Pension, PBOP and SERP	825,001	896,844
Other Long-Term Liabilities	882,688	923,053
Total Deferred Credits and Other Liabilities	6,931,133	6,975,957
Capitalization:
Long-Term Debt	8,147,129	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	1,666,637	1,665,351
Capital Surplus, Paid In	6,201,555	6,192,765
Retained Earnings	2,241,025	2,125,980
Accumulated Other Comprehensive Loss	(41,507)	(46,031)
Treasury Stock	(313,903)	(326,537)
Common Shareholders' Equity	9,753,807	9,611,528
Total Capitalization	18,056,504	17,543,929
Total Liabilities and Capitalization	27,790,445	27,795,537
The Connecticut Light And Power Company [Member]
Current Assets:
Cash	10,486	7,237
Receivables, Net	359,636	319,670
Accounts Receivable from Affiliated Companies	85,134	13,777
Unbilled Revenues	95,491	92,401
Regulatory Assets Current	109,951	150,943
Materials and Supplies	49,525	54,606
Prepayments and Other Current Assets	56,238	53,082
Total Current Assets	766,461	691,716
Property, Plant and Equipment, Net	6,592,833	6,451,259
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,392,529	1,663,147
Other Long-Term Assets	196,935	174,380
Total Deferred Debits and Other Assets	1,589,464	1,837,527
Total Assets	8,948,758	8,980,502
Current Liabilities:
Notes Payable To Affiliated Companies	6,400	287,300
Long-Term Debt - Current Portion	312,000	150,000
Accounts Payable - Current	189,171	201,047
Accounts Payable to Affiliated Companies	44,031	56,531
Obligations to Third Party Suppliers	59,312	73,914
Accrued Taxes	52,900	37,186
Regulatory Liability Current	143,457	93,961
Derivative Liabilities - Current	85,611	92,233
Other Liabilities - Current	94,204	97,530
Total Current Liabilities	987,086	1,089,702
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,610,662	1,510,586
Regulatory Liabilities Long-Term	86,677	93,757
Long-Term Derivative Liabilities	445,342	617,072
Accrued Pension, PBOP and SERP	66,543	95,895
Other Long-Term Liabilities	154,001	163,588
Total Deferred Credits and Other Liabilities	2,363,225	2,480,898
Capitalization:
Long-Term Debt	2,679,591	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	1,753,668	1,682,047
Retained Earnings	989,786	961,482
Accumulated Other Comprehensive Loss	(1,150)	(1,387)
Common Shareholders' Equity	2,802,656	2,702,494
Total Capitalization	5,598,447	5,409,902
Total Liabilities and Capitalization	8,948,758	8,980,502
NSTAR Electric Company [Member]
Current Assets:
Cash	12,975	8,021
Receivables, Net	230,039	209,711
Accounts Receivable from Affiliated Companies	0	27,264
Unbilled Revenues	40,514	41,368
Fuel, Materials and Supplies	51,635	44,236
Regulatory Assets Current	178,640	204,144
Prepayments and Other Current Assets	1,012	36,710
Total Current Assets	514,815	571,454
Property, Plant and Equipment, Net	5,147,239	5,043,887
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,020,990	1,235,156
Other Long-Term Assets	64,963	60,624
Total Deferred Debits and Other Assets	1,085,953	1,295,780
Total Assets	6,748,007	6,911,121
Current Liabilities:
Notes Payable to Banks	194,500	103,500
Long-Term Debt - Current Portion	4,700	301,650
Accounts Payable - Current	150,615	207,559
Accounts Payable to Affiliated Companies	69,949	75,707
Accrued Taxes	44,308	7,946
Deferred Tax Liabilities Current	54,434	50,128
Regulatory Liability Current	89,161	53,958
Other Liabilities - Current	109,048	110,464
Total Current Liabilities	716,715	910,912
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,377,432	1,466,835
Regulatory Liabilities Long-Term	260,480	253,108
Accrued Pension, PBOP and SERP	150,151	118,010
Other Long-Term Liabilities	129,837	142,214
DueToRelatedPartiesNoncurrent	0	64,172
Total Deferred Credits and Other Liabilities	1,917,900	2,044,339
Capitalization:
Long-Term Debt	1,792,702	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	992,625	992,625
Retained Earnings	1,285,065	1,420,828
Common Shareholders' Equity	2,277,690	2,413,453
Total Capitalization	4,113,392	3,955,870
Total Liabilities and Capitalization	6,748,007	6,911,121
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash	337	130
Receivables, Net	69,646	76,331
Accounts Receivable from Affiliated Companies	54	90
Unbilled Revenues	36,971	38,344
Taxes Receivable	45,957	2,180
Fuel, Materials and Supplies	120,723	128,736
Regulatory Assets Current	95,270	92,194
Prepayments and Other Current Assets	21,770	21,920
Total Current Assets	390,728	359,925
Property, Plant and Equipment, Net	2,519,921	2,467,556
Deferred Debits and Other Assets:
Regulatory Assets Long Term	187,592	219,346
Other Long-Term Assets	53,779	39,891
Total Deferred Debits and Other Assets	241,371	259,237
Total Assets	3,152,020	3,086,718
Current Liabilities:
Notes Payable To Affiliated Companies	95,000	86,500
Long-Term Debt - Current Portion	50,000	50,000
Accounts Payable - Current	58,910	82,920
Accounts Payable to Affiliated Companies	18,760	22,040
Deferred Tax Liabilities Current	25,397	28,596
Regulatory Liability Current	36,627	20,643
Other Liabilities - Current	35,440	51,729
Total Current Liabilities	320,134	342,428
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	563,291	500,166
Regulatory Liabilities Long-Term	50,843	51,723
Accrued Pension, PBOP and SERP	15,055	15,272
Other Long-Term Liabilities	46,598	46,247
Total Deferred Credits and Other Liabilities	675,787	613,408
Capitalization:
Long-Term Debt	999,157	999,006
Common Shareholders' Equity:
Common Stock	0	0
Capital Surplus, Paid In	702,652	701,911
Retained Earnings	462,233	438,515
Accumulated Other Comprehensive Loss	(7,943)	(8,550)
Common Shareholders' Equity	1,156,942	1,131,876
Total Capitalization	2,156,099	2,130,882
Total Liabilities and Capitalization	3,152,020	3,086,718
Western Massachusetts Electric Company [Member]
Current Assets:
Cash	1,709	0
Receivables, Net	49,404	49,018
Accounts Receivable from Affiliated Companies	4,445	47,607
Unbilled Revenues	15,617	16,562
Taxes Receivable	15,228	432
Regulatory Assets Current	36,251	43,024
Marketable Securities - Current	19,408	26,628
Prepayments and Other Current Assets	10,730	10,479
Total Current Assets	152,792	193,750
Property, Plant and Equipment, Net	1,418,673	1,381,060
Deferred Debits and Other Assets:
Regulatory Assets Long Term	120,303	146,088
Marketable Securities	38,640	31,243
Other Long-Term Assets	50,438	40,679
Total Deferred Debits and Other Assets	209,381	218,010
Total Assets	1,780,846	1,792,820
Current Liabilities:
Notes Payable To Affiliated Companies	15,900	0
Accounts Payable - Current	28,502	62,961
Accounts Payable to Affiliated Companies	7,533	9,230
Accrued Interest	7,524	7,525
Deferred Tax Liabilities Current	57	13,098
Regulatory Liability Current	44,745	19,858
Other Liabilities - Current	16,518	20,629
CounterPartyDeposit	188	7,688
Total Current Liabilities	120,967	140,989
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	423,013	396,933
Regulatory Liabilities Long-Term	10,317	13,873
Accrued Pension, PBOP and SERP	2,805	3,911
Other Long-Term Liabilities	39,121	28,619
Total Deferred Credits and Other Liabilities	475,256	443,336
Capitalization:
Long-Term Debt	628,932	629,389
Common Shareholders' Equity:
Common Stock	10,866	10,866
Capital Surplus, Paid In	391,035	390,743
Retained Earnings	157,134	181,014
Accumulated Other Comprehensive Loss	(3,344)	(3,517)
Common Shareholders' Equity	555,691	579,106
Total Capitalization	1,184,623	1,208,495
Total Liabilities and Capitalization	$ 1,780,846	$ 1,792,820