The Connecticut Light and Power Company (CNLPM) 10-Q 1 Aug 14 2014 FY Quarterly report Financial data

DOCUMENT_AND_ENTITY_INFORMATIO

DOCUMENT AND ENTITY INFORMATION (USD $)	6 Months Ended
	Jun. 30, 2014	Jul. 31, 2014
Document And Entity [Line Items]	'	'
Entity Registrant Name	'NORTHEAST UTILITIES	'
Document Period End Date	30-Jun-14	'
Document Type	'10-Q	'
Entity Central Index Key	'0000072741	'
Current Fiscal Year End Date	'--12-31	'
Entity Common Stock, Shares Outstanding	'	316,385,790
Entity Public Float	$14,947,688,864	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Current Reporting Status	'Yes	'
Entity Voluntary Filers	'No	'
Entity Well-known Seasoned Issuer	'Yes	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'FY	'
Amendment Flag	'false	'
The Connecticut Light And Power Company [Member]	'	'
Document And Entity [Line Items]	'	'
Entity Registrant Name	'The Connecticut Light and Power Company	'
Entity Central Index Key	'0000023426	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Public Service Company Of New Hampshire [Member]	'	'
Document And Entity [Line Items]	'	'
Entity Registrant Name	'Public Service Company of New Hampshire	'
Entity Central Index Key	'0000315256	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Western Massachusetts Electric Company [Member]	'	'
Document And Entity [Line Items]	'	'
Entity Registrant Name	'Western Massachusetts Electric Company	'
Entity Central Index Key	'0000106170	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
NSTAR Electric Company [Member]	'	'
Document And Entity [Line Items]	'	'
Entity Registrant Name	'NSTAR Electric Company	'
Entity Central Index Key	'0000013372	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
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

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating Revenues	$1,677,614	$1,635,862	$3,968,204	$3,630,885
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	624,211	488,302	1,602,362	1,236,111
Operations and Maintenance	373,234	357,169	724,922	703,261
Depreciation	152,207	159,553	303,014	314,530
Amortization of Regulatory Assets/(Liabilities), Net	-3,542	54,574	54,356	108,623
Amortization of Rate Reduction Bonds	0	8,082	0	42,581
Energy Efficiency Programs	102,711	94,142	241,536	199,913
Taxes Other Than Income Taxes	134,803	123,464	280,335	256,345
Total Operating Expenses	1,383,624	1,285,286	3,206,525	2,861,364
Operating Income	293,990	350,576	761,679	769,521
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	87,491	85,999	174,868	171,294
Other Interest	5,004	851	7,603	-8,188
Total Interest Expense	92,495	86,850	182,471	163,106
Other Income/(Loss), Net	5,526	4,944	7,194	12,710
Income Before Income Tax Expense	207,021	268,670	586,402	619,125
Income Tax Expense	77,774	95,606	219,319	216,093
Net Income	129,247	173,064	367,083	403,032
Net Income Attributable to Noncontrolling Interests	1,880	2,043	3,759	3,922
Net Income Attributable to Controlling Interests	127,367	171,021	363,324	399,110
Diluted Earnings Per Common Share	$0.40	$0.54	$1.15	$1.26
Basic Earnings Per Common Share	$0.40	$0.54	$1.15	$1.27
Common Stock Dividends Per Share Declared	$0.39	$0.37	$0.79	$0.74
Weighted Average Common Shares Outstanding:	'	'	'	'
Basic	315,950,510	315,154,130	315,742,511	315,141,956
Diluted	317,112,801	315,962,619	317,002,461	315,982,578
The Connecticut Light And Power Company [Member]	'	'	'	'
Operating Revenues	587,324	569,329	1,321,938	1,193,425
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	199,785	184,854	481,165	414,113
Operations and Maintenance	131,762	123,760	241,276	232,655
Depreciation	46,581	45,122	92,712	87,570
Amortization of Regulatory Assets/(Liabilities), Net	19,615	463	49,546	11,249
Energy Efficiency Programs	35,296	20,854	77,991	43,668
Taxes Other Than Income Taxes	62,159	57,506	129,111	117,697
Total Operating Expenses	495,198	432,559	1,071,801	906,952
Operating Income	92,126	136,770	250,137	286,473
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	34,639	32,683	67,548	65,318
Other Interest	2,831	1,301	4,165	-1,640
Total Interest Expense	37,470	33,984	71,713	63,678
Other Income/(Loss), Net	3,130	2,897	4,202	7,084
Income Before Income Tax Expense	57,786	105,683	182,626	229,879
Income Tax Expense	20,401	37,826	65,942	77,014
Net Income	37,385	67,857	116,684	152,865
NSTAR Electric Company [Member]	'	'	'	'
Operating Revenues	561,513	570,420	1,227,701	1,162,677
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	242,907	189,843	561,989	403,896
Operations and Maintenance	78,981	87,891	164,905	180,192
Depreciation	46,915	45,441	93,540	90,882
Amortization of Regulatory Assets/(Liabilities), Net	-1,517	53,554	14,147	100,548
Amortization of Rate Reduction Bonds	0	0	0	15,054
Energy Efficiency Programs	40,255	50,679	88,584	102,382
Taxes Other Than Income Taxes	32,458	30,491	64,610	62,665
Total Operating Expenses	439,999	457,899	987,775	955,619
Operating Income	121,514	112,521	239,926	207,058
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	19,732	19,809	40,489	39,401
Other Interest	960	-2,620	1,263	-6,288
Total Interest Expense	20,692	17,189	41,752	33,113
Other Income/(Loss), Net	-246	375	-277	1,149
Income Before Income Tax Expense	100,576	95,707	197,897	175,094
Income Tax Expense	40,447	37,676	79,681	68,941
Net Income	60,129	58,031	118,216	106,153
Public Service Company Of New Hampshire [Member]	'	'	'	'
Operating Revenues	211,626	216,113	511,458	489,942
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	68,349	50,073	183,595	151,097
Operations and Maintenance	70,249	62,400	132,462	122,129
Depreciation	24,464	22,947	48,679	45,515
Amortization of Regulatory Assets/(Liabilities), Net	-20,393	1,081	-7,831	-1,969
Amortization of Rate Reduction Bonds	0	4,991	0	19,748
Energy Efficiency Programs	3,292	3,376	7,131	7,046
Taxes Other Than Income Taxes	16,635	16,918	34,348	33,932
Total Operating Expenses	162,596	161,786	398,384	377,498
Operating Income	49,030	54,327	113,074	112,444
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	11,390	10,811	22,916	22,606
Other Interest	-391	337	55	709
Total Interest Expense	10,999	11,148	22,971	23,315
Other Income/(Loss), Net	946	632	1,212	1,662
Income Before Income Tax Expense	38,977	43,811	91,315	90,791
Income Tax Expense	14,897	16,617	34,597	34,602
Net Income	24,080	27,194	56,718	56,189
Western Massachusetts Electric Company [Member]	'	'	'	'
Operating Revenues	108,289	115,015	245,698	239,968
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	37,619	32,254	87,050	72,298
Operations and Maintenance	23,686	23,136	46,265	44,064
Depreciation	10,317	9,310	20,638	18,280
Amortization of Regulatory Assets/(Liabilities), Net	343	685	741	814
Amortization of Rate Reduction Bonds	0	3,091	0	7,780
Energy Efficiency Programs	10,249	7,925	22,114	16,240
Taxes Other Than Income Taxes	8,396	6,206	16,479	12,494
Total Operating Expenses	90,610	82,607	193,287	171,970
Operating Income	17,679	32,408	52,411	67,998
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	6,104	6,078	12,165	12,032
Other Interest	603	198	188	537
Total Interest Expense	6,707	6,276	12,353	12,569
Other Income/(Loss), Net	594	419	1,168	1,423
Income Before Income Tax Expense	11,566	26,551	41,226	56,852
Income Tax Expense	4,548	10,137	16,106	21,836
Net Income	$7,018	$16,414	$25,120	$35,016

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Income	$129,247	$173,064	$367,083	$403,032
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	510	514	1,019	1,030
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	218	-591	458	-772
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	2,086	1,506	3,047	3,127
Other Comprehensive Income (Loss), Net of Tax, Total	2,814	1,429	4,524	3,385
Comprehensive Income Attributable to Noncontrolling Interests	-1,880	-2,043	-3,759	-3,922
Comprehensive Income	130,181	172,450	367,848	402,495
The Connecticut Light And Power Company [Member]	'	'	'	'
Net Income	37,385	67,857	116,684	152,865
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111	111	222	222
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	7	-20	15	-26
Other Comprehensive Income (Loss), Net of Tax, Total	118	91	237	196
Comprehensive Income	37,503	67,948	116,921	153,061
NSTAR Electric Company [Member]	'	'	'	'
Net Income	60,129	58,031	118,216	106,153
Public Service Company Of New Hampshire [Member]	'	'	'	'
Net Income	24,080	27,194	56,718	56,189
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	291	291	581	582
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	12	-34	26	-45
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	0	0	0	-3
Other Comprehensive Income (Loss), Net of Tax, Total	303	257	607	534
Comprehensive Income	24,383	27,451	57,325	56,723
Western Massachusetts Electric Company [Member]	'	'	'	'
Net Income	7,018	16,414	25,120	35,016
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	84	84	169	169
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	2	-6	4	-8
Other Comprehensive Income (Loss), Net of Tax, Total	86	78	173	161
Comprehensive Income	$7,104	$16,492	$25,293	$35,177

CONSOLIDATED_STATEMENT_OF_CASH

CONSOLIDATED STATEMENT OF CASH FLOWS (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Operating Activities:	'	'
Net Income	$367,083	$403,032
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	303,014	314,530
Deferred Income Tax Expense (Benefit)	133,149	256,294
Pension and PBOP Expense, Net of PBOP Contributions	47,558	97,671
Pension and Other Postretirement Benefit Contributions	-40,640	-122,826
Regulatory (Underrecoveries)/Overrecoveries, Net	164,388	-4,793
Amortization of Regulatory Assets/(Liabilities), Net	54,356	108,623
Amortization of Rate Reduction Bonds	0	42,581
Other Noncash Income (Expense)	-9,359	19,932
Proceeds from DOE Damages Claim, Net	125,658	'
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-57,570	-101,229
Inventory	26,633	10,964
Taxes Receivable/(Accrued)	-62,900	-58,350
Change in Accounts Payable	-112,954	-127,379
Other Current Assets and Liabilities	-41,753	-70,026
Net Cash Flows Provided by Operating Activities	896,663	769,024
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-724,043	-700,252
Proceeds from Sales of Marketable Securities	256,309	342,251
Purchases of Marketable Securities	-257,168	-424,096
DecreaseInRestrictedCash	2,894	65,121
Other Investing Activities	579	-843
Net Cash Flows Used in Investing Activities	-721,429	-717,819
Financing Activities:	'	'
Cash Dividends on Common Stock	-237,161	-232,068
Cash Dividends on Preferred Stock	-3,759	-3,922
Increase/(Decrease) in Short-Term Debt	-213,000	-720,500
Issuance of Long-Term Debt	650,000	1,350,000
Retirements of Long-Term Debt	-376,650	-360,635
Retirements of Rate Reduction Bonds	0	-82,139
Other Financing Activities	-3,932	-11,634
Net Cash Flows Provided by/(Used in) Financing Activities	-184,502	-60,898
Net Increase/(Decrease) in Cash	-9,268	-9,693
Cash - Beginning of Year	43,364	45,748
Cash - End of Year	34,096	36,055
The Connecticut Light And Power Company [Member]	'	'
Operating Activities:	'	'
Net Income	116,684	152,865
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	92,712	87,570
Deferred Income Tax Expense (Benefit)	43,253	99,045
Pension and PBOP Expense, Net of PBOP Contributions	5,973	13,826
Regulatory (Underrecoveries)/Overrecoveries, Net	18,156	-36,902
Amortization of Regulatory Assets/(Liabilities), Net	49,546	11,249
Other Noncash Income (Expense)	-3,428	-13,476
Proceeds from DOE Damages Claim	65,370	0
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-129,209	-33,976
Taxes Receivable/(Accrued)	27,679	-14,081
Change in Accounts Payable	-26,995	-95,487
Other Current Assets and Liabilities	15,705	7,548
Net Cash Flows Provided by Operating Activities	275,446	178,181
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-221,365	-184,875
Other Investing Activities	1,575	884
Net Cash Flows Used in Investing Activities	-219,790	-183,991
Financing Activities:	'	'
Cash Dividends on Common Stock	-85,600	-76,000
Cash Dividends on Preferred Stock	-2,779	-2,779
Increase/(Decrease) in Short-Term Debt	0	-89,000
Issuance of Long-Term Debt	250,000	400,000
Increase/(Decrease) in Notes Payable to Affiliate	-280,900	-215,800
Capital Contributions from NU Parent	70,000	'
Other Financing Activities	-3,128	-6,345
Net Cash Flows Provided by/(Used in) Financing Activities	-52,407	10,076
Net Increase/(Decrease) in Cash	3,249	4,266
Cash - Beginning of Year	7,237	1
Cash - End of Year	10,486	4,267
NSTAR Electric Company [Member]	'	'
Operating Activities:	'	'
Net Income	118,216	106,153
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Bad Debt Expense	12,272	11,307
Depreciation	93,540	90,882
Deferred Income Tax Expense (Benefit)	-21,724	28,750
Pension and PBOP Expense, Net of PBOP Contributions	-8,281	-5,139
Regulatory (Underrecoveries)/Overrecoveries, Net	63,955	-33,901
Amortization of Regulatory Assets/(Liabilities), Net	14,147	100,548
Amortization of Rate Reduction Bonds	0	15,054
Other Noncash Income (Expense)	-29,142	-47,574
Proceeds from DOE Damages Claim	29,113	'
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-31,746	-60,174
Inventory	-7,399	3,294
Taxes Receivable/(Accrued)	65,692	-39,813
Change in Accounts Payable	-21,511	-8,686
Other Current Assets and Liabilities	3,158	-11,702
IncreaseDecreaseInAccountsPayableRelatedParties	107,363	-57,369
Net Cash Flows Provided by Operating Activities	387,653	91,630
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-213,508	-207,380
DecreaseInRestrictedCash	581	38,429
Other Investing Activities	-5	77
Net Cash Flows Used in Investing Activities	-212,932	-168,874
Financing Activities:	'	'
Cash Dividends on Common Stock	-253,000	-56,000
Cash Dividends on Preferred Stock	-980	-1,143
Increase/(Decrease) in Short-Term Debt	91,000	-23,000
Issuance of Long-Term Debt	300,000	200,000
Retirements of Long-Term Debt	-301,650	-1,650
Retirements of Rate Reduction Bonds	'	-43,493
Other Financing Activities	-5,137	0
Net Cash Flows Provided by/(Used in) Financing Activities	-169,767	74,714
Net Increase/(Decrease) in Cash	4,954	-2,530
Cash - Beginning of Year	8,021	13,695
Cash - End of Year	12,975	11,165
Public Service Company Of New Hampshire [Member]	'	'
Operating Activities:	'	'
Net Income	56,718	56,189
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	48,679	45,515
Deferred Income Tax Expense (Benefit)	61,093	25,450
Pension and PBOP Expense, Net of PBOP Contributions	3,249	14,228
Pension and Other Postretirement Benefit Contributions	-833	-45,721
Regulatory (Underrecoveries)/Overrecoveries, Net	18,849	4,844
Amortization of Regulatory Assets/(Liabilities), Net	-7,831	-1,969
Amortization of Rate Reduction Bonds	0	19,748
Other Noncash Income (Expense)	4,386	3,123
Proceeds from DOE Damages Claim	13,103	'
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	3,500	597
Inventory	8,013	-13,289
Taxes Receivable/(Accrued)	-55,243	21,584
Change in Accounts Payable	-7,146	26,159
Other Current Assets and Liabilities	-4,166	-17,743
Net Cash Flows Provided by Operating Activities	142,371	138,715
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-117,387	-109,565
DecreaseInRestrictedCash	-45	22,039
Other Investing Activities	-56	-13
Net Cash Flows Used in Investing Activities	-117,488	-87,539
Financing Activities:	'	'
Cash Dividends on Common Stock	-33,000	-34,000
Increase/(Decrease) in Short-Term Debt	8,500	118,900
Retirements of Long-Term Debt	'	-108,985
Retirements of Rate Reduction Bonds	0	-29,294
Other Financing Activities	-176	-225
Net Cash Flows Provided by/(Used in) Financing Activities	-24,676	-53,604
Net Increase/(Decrease) in Cash	207	-2,428
Cash - Beginning of Year	130	2,493
Cash - End of Year	337	65
Western Massachusetts Electric Company [Member]	'	'
Operating Activities:	'	'
Net Income	25,120	35,016
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	20,638	18,280
Deferred Income Tax Expense (Benefit)	15,234	33,317
Regulatory (Underrecoveries)/Overrecoveries, Net	28,115	-5,094
Amortization of Regulatory Assets/(Liabilities), Net	741	814
Amortization of Rate Reduction Bonds	0	7,780
Other Noncash Income (Expense)	1,462	572
Proceeds from DOE Damages Claim	18,073	'
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	44,859	-8,681
Taxes Receivable/(Accrued)	-19,555	21,081
Change in Accounts Payable	-26,494	21,389
Other Current Assets and Liabilities	-11,587	-5,166
Net Cash Flows Provided by Operating Activities	96,606	119,308
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-61,470	-96,051
Proceeds from Sales of Marketable Securities	44,449	41,604
Purchases of Marketable Securities	-44,754	-41,961
Other Investing Activities	0	4,601
Net Cash Flows Used in Investing Activities	-61,775	-91,807
Financing Activities:	'	'
Cash Dividends on Common Stock	-49,000	-20,000
Increase/(Decrease) in Notes Payable to Affiliate	15,900	3,300
Retirements of Rate Reduction Bonds	0	-9,352
Other Financing Activities	-22	-31
Net Cash Flows Provided by/(Used in) Financing Activities	-33,122	-26,083
Net Increase/(Decrease) in Cash	1,709	1,418
Cash - Beginning of Year	0	1
Cash - End of Year	$1,709	$1,419

SUMMARY_OF_SIGNIFICANT_ACCOUNT

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Significant Accounting Policies [Text Block]	'
	NORTHEAST UTILITIES AND SUBSIDIARIES
	THE CONNECTICUT LIGHT AND POWER COMPANY
	NSTAR ELECTRIC COMPANY AND SUBSIDIARY
	PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE AND SUBSIDIARY
	WESTERN MASSACHUSETTS ELECTRIC COMPANY
	COMBINED NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (Unaudited)
	Refer to the Glossary of Terms included in this combined Quarterly Report on Form 10-Q for abbreviations and acronyms used throughout the combined notes to the unaudited condensed consolidated financial statements.
	1.       SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	A.       Basis of Presentation
	NU is a public utility holding company primarily engaged through its wholly owned regulated utility subsidiaries in the energy delivery business. NU's wholly owned regulated utility subsidiaries consist of CL&P, NSTAR Electric, PSNH, WMECO, Yankee Gas and NSTAR Gas. NU provides energy delivery service to approximately 3.6 million electric and natural gas customers through these six regulated utilities in Connecticut, Massachusetts and New Hampshire.
	The unaudited condensed consolidated financial statements of NU, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements of NU, NSTAR Electric and PSNH and the unaudited condensed financial statements of CL&P and WMECO are herein collectively referred to as the "financial statements."
	The combined notes to the financial statements have been prepared pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures included in annual financial statements prepared in accordance with GAAP have been omitted pursuant to such rules and regulations. The accompanying financial statements should be read in conjunction with the entirety of this combined Quarterly Report on Form 10-Q, the first quarter 2014 combined Quarterly Report on Form 10-Q and the 2013 combined Annual Report on Form 10-K of NU, CL&P, NSTAR Electric, PSNH and WMECO, which were filed with the SEC. The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	The financial statements contain, in the opinion of management, all adjustments (including normal, recurring adjustments) necessary to present fairly NU's, CL&P's, NSTAR Electric's, PSNH's and WMECO's financial position as of June 30, 2014 and December 31, 2013, the results of operations and comprehensive income for the three and six months ended June 30, 2014 and 2013, and the cash flows for the six months ended June 30, 2014 and 2013. The results of operations and comprehensive income for the three and six months ended June 30, 2014 and 2013, and the cash flows for the six months ended June 30, 2014 and 2013 are not necessarily indicative of the results expected for a full year. The demand for electricity and natural gas is affected by weather conditions, economic conditions, and consumer conservation (including company-sponsored energy efficiency programs). Electric energy sales and revenues are typically higher in the winter and summer months than in the spring and fall months. Natural gas sales and revenues are typically higher in the winter months than during other periods of the year.
	NU consolidates CYAPC and YAEC as CL&P's, NSTAR Electric's, PSNH's and WMECO's combined ownership interest in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and WMECO and the CYAPC and YAEC companies have been eliminated in consolidation of the NU financial statements. For CL&P, NSTAR Electric, PSNH and WMECO, the investments in CYAPC and YAEC continue to be accounted for under the equity method.
	NU's utility subsidiaries are subject to the application of accounting guidance for entities with rate-regulated operations that considers the effect of regulation resulting from differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. NU's utility subsidiaries' energy delivery business is subject to rate-regulation that is based on cost recovery and meets the criteria for application of rate-regulated accounting. See Note 2, "Regulatory Accounting," for further information.
	Certain reclassifications of prior period data were made in the accompanying balance sheets for NU, CL&P, NSTAR Electric and PSNH, and in the statements of income for NU, NSTAR Electric, PSNH and WMECO. These reclassifications were made to conform to the current period presentation.
	B.       Accounting Standards
	Recently Adopted Accounting Standards: On January 1, 2014, as required, NU prospectively adopted the Financial Accounting Standards Board's (FASB) final Accounting Standards Updates (ASU) that required presentation of certain unrecognized tax benefits as reductions to deferred tax assets. Implementation of this guidance had an immaterial impact on the balance sheets and no impact on the results of operations or cash flows of NU, CL&P, NSTAR Electric, PSNH and WMECO.
	Accounting Standards Issued but not Yet Adopted: In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, effective January 1, 2017, which amends existing revenue recognition guidance and is required to be applied retrospectively (either to each reporting period presented or cumulatively at the date of initial application). Management is reviewing the requirements of the new ASU, however the ASU's impact is not expected to have a material impact on the financial statements of NU, CL&P, NSTAR Electric, PSNH and WMECO.
	C.       Provision for Uncollectible Accounts
	NU, including CL&P, NSTAR Electric, PSNH and WMECO, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectibility from individual customers. Management continuously assesses the collectibility of receivables, and adjusts collectibility estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the accounts are terminated and these balances are deemed to be uncollectible. The provision for uncollectible accounts, which is included in Receivables, Net on the balance sheets, was as follows:
	(Millions of Dollars)			As of June 30, 2014			As of December 31, 2013
	NU			$	197.4		$	171.3
	CL&P				91.8			82
	NSTAR Electric				44.4			41.7
	PSNH				9.2			7.4
	WMECO				12.9			10
	D.       Fair Value Measurements
	Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases or normal sales" (normal) and to the marketable securities held in trusts. Fair value measurement guidance is also applied to investment valuations used to calculate the funded status of pension and PBOP plans and nonrecurring fair value measurements of nonfinancial assets such as goodwill and AROs.
	Fair Value Hierarchy: In measuring fair value, NU uses observable market data when available and minimizes the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. NU evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and NU's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below:
	Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date.  Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable.
	Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products.
	Determination of Fair Value: The valuation techniques and inputs used in NU's fair value measurements are described in Note 4, "Derivative Instruments," Note 5, "Marketable Securities," and Note 9, "Fair Value of Financial Instruments," to the financial statements.
	E.       Other Income, Net
	Items included within Other Income, Net on the statements of income primarily consist of investment income/(loss), interest income, AFUDC related to equity funds, and equity in earnings. Investment income/(loss) primarily relates to debt and equity securities held in trust. For further information, see Note 5, "Marketable Securities," to the financial statements. For CL&P, NSTAR Electric, PSNH and WMECO, equity in earnings relate to investments in CYAPC, YAEC and MYAPC as well as NSTAR Electric's investment in two regional transmission companies, which are all accounted for on the equity method. On an NU consolidated basis, equity in earnings relate to the investment in MYAPC and NU's investment in two regional transmission companies.
	F.       Other Taxes
	Gross receipts taxes levied by the state of Connecticut are collected by CL&P and Yankee Gas from their respective customers. These gross receipts taxes are shown on a gross basis with collections in Operating Revenues and payments in Taxes Other Than Income Taxes on the statements of income as follows:
		For the Three Months Ended						For the Six Months Ended
	(Millions of Dollars)	30-Jun-14			30-Jun-13			30-Jun-14		30-Jun-13
	NU	$	35.2		$	33		$	79.6	$	71.4
	CL&P		30.9			29.8			66.5		61.8
	Certain sales taxes are also collected by NU's companies that serve customers in Connecticut and Massachusetts as agents for state and local governments and are recorded on a net basis with no impact on the statements of income.
	G.			Supplemental Cash Flow Information
	Non-cash investing activities include plant additions included in Accounts Payable as follows:
	(Millions of Dollars)				As of June 30, 2014			As of June 30, 2013
	NU				$	125.5		$	109.5
	CL&P					54			28.3
	NSTAR Electric					21.6			33.4
	PSNH					14.8			15.5
	WMECO					9.9			17
	In the first half of 2014, as a result of awards issued to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 8C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," NU recognized total proceeds of $125.7 million, which were net of $80.6 million in proceeds CY and YAEC returned to non-affiliated member companies.

REGULATORY_ACCOUNTING

REGULATORY ACCOUNTING	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Public Utilities Disclosure [Text Block]	'
	2.       REGULATORY ACCOUNTING
	The rates charged to the customers of NU's Regulated companies are designed to collect each company's costs to provide service, including a return on investment. Therefore, the accounting policies of the Regulated companies follow the application of accounting guidance for entities with rate-regulated operations and reflect the effects of the rate-making process.
	Management believes it is probable that each of the Regulated companies will recover their respective investments in long-lived assets, including regulatory assets. If management were to determine that it could no longer apply the accounting guidance applicable to rate-regulated enterprises to any of the Regulated companies' operations, or that management could not conclude it is probable that costs would be recovered from customers in future rates, the costs would be charged to net income in the period in which the determination is made.
	Regulatory Assets: The components of regulatory assets are as follows:
		As of June 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Benefit Costs	$	1,146.70		$	1,240.20
	Derivative Liabilities		431.4			638
	Income Taxes, Net		631.8			626.2
	Storm Restoration Costs		503.9			589.6
	Goodwill-related		515.7			525.9
	Regulatory Tracker Mechanisms		275.1			323.4
	Contractual Obligations - Yankee Companies		128.4			154.2
	Buy Out Agreements for Power Contracts		56.7			70.2
	Other Regulatory Assets		117			126.8
	Total Regulatory Assets		3,806.70			4,294.50
	Less: Current Portion		467.2			535.8
	Total Long-Term Regulatory Assets	$	3,339.50		$	3,758.70
			As of June 30, 2014									As of December 31, 2013
						NSTAR								NSTAR
	(Millions of Dollars)		CL&P			Electric		PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Benefit Costs		$	251.9		$	323.4	$	81.6	$	46.2	$	297.7	$	496.7	$	100.6	$	57.3
	Derivative Liabilities			424.6			6.3		-		-		630.4		7.7		-		-
	Income Taxes, Net			426.2			81.4		38		40.8		415.5		84		40.3		43.7
	Storm Restoration Costs			328			107.2		34.7		34		397.8		109.3		43.7		38.8
	Goodwill-related			-			442.8		-		-		-		451.5		-		-
	Regulatory Tracker Mechanisms			8.1			131.8		87.9		20.7		8		169.5		83.3		32.6
	Buy Out Agreements for Power Contracts			-			52		4.7		-		-		64.7		5.5		-
	Other Regulatory Assets			63.7			54.7		36		14.9		64.6		55.9		38.1		16.7
	Total Regulatory Assets			1,502.50			1,199.60		282.9		156.6		1,814.00		1,439.30		311.5		189.1
	Less: Current Portion			110			178.6		95.3		36.3		150.9		204.1		92.2		43
	Total Long-Term Regulatory Assets		$	1,392.50		$	1,021.00	$	187.6	$	120.3	$	1,663.10	$	1,235.20	$	219.3	$	146.1
	Benefit Costs: For information related to the Regulated companies' pension and other postretirement benefits, see Note 7, "Pension Benefits and Postretirement Benefits Other Than Pensions."
	Storm Restoration Costs: On March 12, 2014, the PURA approved recovery of $365 million of deferred storm restoration costs associated with five major storms that occurred in 2011 and 2012. CL&P will recover the $365 million with carrying charges in its distribution rates over a six-year period beginning December 1, 2014. On June 17, 2014, the PURA ordered CL&P to use the DOE Phase II Damages proceeds of $65.4 million to offset the $365 million in 2011 and 2012 deferred storm restoration costs, which are reflected in the deferred storm restoration costs regulatory asset. For further information on the DOE Phase II Damages proceeds received from the Yankee Companies, see Note 8C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," to the financial statements.
	Regulatory Costs in Other Long-Term Assets: The Regulated companies had $64.5 million ($3.4 million for CL&P, $33.9 million for NSTAR Electric, and $12 million for WMECO) and $65.1 million ($7.3 million for CL&P, $33.4 million for NSTAR Electric, and $10.1 million for WMECO) of additional regulatory costs as of June 30, 2014 and December 31, 2013, respectively, that were included in Other Long-Term Assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates.
	Regulatory Liabilities: The components of regulatory liabilities are as follows:
		As of June 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Cost of Removal	$	435.3		$	435.1
	Regulatory Tracker Mechanisms		305.2			151.2
	AFUDC - Transmission		67.4			68.1
	Other Regulatory Liabilities		56			52.9
	Total Regulatory Liabilities		863.9			707.3
	Less: Current Portion		359.9			204.3
	Total Long-Term Regulatory Liabilities	$	504		$	503
			As of June 30, 2014									As of December 31, 2013
						NSTAR								NSTAR
	(Millions of Dollars)		CL&P			Electric		PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Cost of Removal		$	22.8		$	255.7	$	48.7	$	-	$	29.1	$	250	$	49.7	$	-
	Regulatory Tracker Mechanisms			143.2			60.2		34.8		45.1		95.6		21.9		21.6		21.1
	AFUDC - Transmission			54.2			4		-		9.2		54.7		4.1		-		9.3
	Other Regulatory Liabilities			10			29.8		3.9		0.7		8.4		31.1		1		3.4
	Total Regulatory Liabilities			230.2			349.7		87.4		55		187.8		307.1		72.3		33.8
	Less: Current Portion			143.5			89.2		36.6		44.7		94		54		20.6		19.9
	Total Long-Term Regulatory Liabilities		$	86.7		$	260.5	$	50.8	$	10.3	$	93.8	$	253.1	$	51.7	$	13.9
	As a result of two FERC orders issued on June 19, 2014 in the pending base ROE complaint proceedings described in Note 8E, "Commitments and Contingencies – FERC Base ROE Complaints," in the second quarter of 2014, the Company recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact of these rulings. The aggregate pre-tax charge totaled $54.7 million at NU, which represented reserves of $31.4 million at CL&P, $10.3 million at NSTAR Electric, $3.8 million at PSNH and $9.2 million at WMECO. As of June 30, 2014, the cumulative reserves totaled $79.3 million at NU, $44.7 million at CL&P, $16.2 million at NSTAR Electric, $6.2 million at PSNH and $12.2 million at WMECO. As of December 31, 2013, as a result of the FERC ALJ initial decision in the third quarter of 2013, the Company had an aggregate pre-tax reserve of $24.6 million at NU, which represented reserves of $13.3 million at CL&P, $5.9 million at NSTAR Electric, $2.4 million at PSNH and $3 million at WMECO. These reserves were recorded in each electric subsidiary's respective transmission regulatory tracker mechanism and as a reduction of operating revenues.
	As a result of awards issued to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 8C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," the Yankee Companies returned the DOE Phase II Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, for the benefit of their respective customers, effective June 1, 2014. CL&P's refund obligation to customers of $65.4 million was recorded as an offset to the deferred storm restoration costs regulatory asset, as directed by PURA. NSTAR Electric's, PSNH's and WMECO's refund obligation to customers of $29.1 million, $13.1 million and $18.1 million, respectively, was recorded as a regulatory liability in each electric subsidiary's respective regulatory tracker mechanisms.

PROPERTY_PLANT_AND_ACCUMULATED

PROPERTY, PLANT AND ACCUMULATED DEPRECIATION	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Property Plant And Equipment Disclosure [Text Block]	'
	3.       PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION
	The following tables summarize the investments in utility property, plant and equipment by asset category:
				As of June 30, 2014			As of December 31, 2013
	(Millions of Dollars)			NU			NU
	Distribution - Electric			$	12,145.00		$	11,950.20
	Distribution - Natural Gas				2,467.40			2,425.90
	Transmission				6,508.00			6,412.50
	Generation				1,167.90			1,152.30
	Electric and Natural Gas Utility				22,288.30			21,940.90
	Other (1)				506.5			508.7
	Property, Plant and Equipment, Gross				22,794.80			22,449.60
	Less: Accumulated Depreciation
		Electric and Natural Gas Utility			-5,575.80			-5,387.00
		Other			-207.7			-196.2
	Total Accumulated Depreciation				-5,783.50			-5,583.20
	Property, Plant and Equipment, Net				17,011.30			16,866.40
	Construction Work in Progress				967.4			709.8
	Total Property, Plant and Equipment, Net			$	17,978.70		$	17,576.20
	(1)       These assets represent unregulated property and are primarily comprised of building improvements, computer software, hardware and equipment and telecommunications assets at NU's unregulated companies.
		As of June 30, 2014										As of December 31, 2013
					NSTAR									NSTAR
	(Millions of Dollars)	CL&P			Electric			PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Distribution	$	5,035.20		$	4,754.40		$	1,629.10	$	766.3	$	4,930.70	$	4,694.70	$	1,608.20	$	756.6
	Transmission		3,108.10			1,798.90			713.5		841.1		3,071.90		1,772.30		695.7		826.4
	Generation		-			-			1,134.00		33.9		-		-		1,131.20		21.1
	Property, Plant and Equipment, Gross		8,143.30			6,553.30			3,476.60		1,641.30		8,002.60		6,467.00		3,435.10		1,604.10
	Less: Accumulated Depreciation		-1,867.90			-1,700.60			-1,045.30		-283.7		-1,804.10		-1,631.30		-1,021.80		-271.5
	Property, Plant and Equipment, Net		6,275.40			4,852.70			2,431.30		1,357.60		6,198.50		4,835.70		2,413.30		1,332.60
	Construction Work in Progress		317.4			294.5			88.6		61.1		252.8		208.2		54.3		48.5
	Total Property, Plant and Equipment, Net	$	6,592.80		$	5,147.20		$	2,519.90	$	1,418.70	$	6,451.30	$	5,043.90	$	2,467.60	$	1,381.10

DERIVATIVE_INSTRUMENTS

DERIVATIVE INSTRUMENTS	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Derivative Instruments and Hedging Activities Disclosure [Text Block]	'
	4.       DERIVATIVE INSTRUMENTS
	The Regulated companies purchase and procure energy and energy-related products for their customers, which are subject to price volatility. The costs associated with supplying energy to customers are recoverable through customer rates. The Regulated companies manage the risks associated with the price volatility of energy and energy-related products through the use of derivative and nonderivative contracts.
	Many of the derivative contracts meet the definition of, and are designated as, normal and qualify for accrual accounting under the applicable accounting guidance. The costs and benefits of derivative contracts that meet the definition of normal are recognized in Operating Expenses or Operating Revenues on the statements of income, as applicable, as electricity or natural gas is delivered.
	Derivative contracts that are not designated as normal are recorded at fair value as current or long-term Derivative Assets or Derivative Liabilities on the balance sheets. For the Regulated companies, regulatory assets or regulatory liabilities are recorded to offset the fair values of derivatives, as costs are recovered from, or refunded to, customers in their respective energy supply rates. For NU's unregulated wholesale marketing contracts that expired on December 31, 2013, changes in fair values of derivatives were included in Net Income.
	The gross fair values of derivative assets and liabilities with the same counterparty are offset and reported as net Derivative Assets or Derivative Liabilities, with current and long-term portions, on the balance sheets. Cash collateral posted or collected under master netting agreements is recorded as an offset to the derivative asset or liability. The following tables present the gross fair values of contracts categorized by risk type and the net amount recorded as current or long-term derivative asset or liability:
			As of June 30, 2014
			Commodity Supply and						Net Amount Recorded as
	(Millions of Dollars)		Price Risk Management			Netting (1)			Derivative Asset/(Liability)
	Current Derivative Assets:
	Level 2:
		NU (1)	$	0.4		$	-0.1		$	0.3
	Level 3:
		NU, CL&P (1)		16.4			-4.8			11.6
	Long-Term Derivative Assets:
	Level 3:
		NU, CL&P (1)	$	111.7		$	-17		$	94.7
	Current Derivative Liabilities:
	Level 2:
		NU (1)	$	-0.7		$	0.2		$	-0.5
	Level 3:
		NU		-87.8			-			-87.8
		CL&P		-85.6			-			-85.6
		NSTAR Electric		-2.2			-			-2.2
	Long-Term Derivative Liabilities:
	Level 3:
		NU	$	-449.4		$	-		$	-449.4
		CL&P		-445.3			-			-445.3
		NSTAR Electric		-4.1			-			-4.1
			As of December 31, 2013
			Commodity Supply and						Net Amount Recorded as
	(Millions of Dollars)		Price Risk Management			Netting (1)			Derivative Asset/(Liability)
	Current Derivative Assets:
	Level 2:
		NU (1)	$	1.9		$	-0.3		$	1.6
	Level 3:
		NU (1)		18.4			-9.8			8.6
		CL&P (1)		17.1			-9.8			7.3
		NSTAR Electric		1.2			-			1.2
	Long-Term Derivative Assets:
	Level 2:
		NU	$	0.2		$	-		$	0.2
	Level 3:
		NU (1)		116.2			-42.2			74
		CL&P (1)		113.6			-42.2			71.4
	Current Derivative Liabilities:
	Level 3:
		NU	$	-93.7		$	-		$	-93.7
		CL&P		-92.2			-			-92.2
		NSTAR Electric		-1.5			-			-1.5
	Long-Term Derivative Liabilities:
	Level 3:
		NU	$	-624.1		$	-		$	-624.1
		CL&P		-617.1			-			-617.1
		NSTAR Electric		-7			-			-7
	Amounts represent derivative assets and liabilities that NU elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists.
	For further information on the fair value of derivative contracts, see Note 1D, "Summary of Significant Accounting Policies - Fair Value Measurements," to the financial statements.
	Derivatives Not Designated as Hedges
	Commodity Supply and Price Risk Management: As required by regulation, CL&P, along with UI, has capacity-related contracts with generation facilities. CL&P has a sharing agreement with UI, with 80 percent of each contract allocated to CL&P and 20 percent allocated to UI. The combined capacity of these contracts is 787 MW. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the forward capacity market price received in the ISO-NE capacity markets. In addition, CL&P has a contract to purchase 0.1 million MWh of energy per year through 2020.
	NSTAR Electric has a renewable energy contract to purchase 0.1 million MWh of energy per year through 2018 and a capacity-related contract to purchase up to 35 MW per year through 2019.
	As of June 30, 2014 and December 31, 2013, NU had NYMEX future contracts in order to reduce variability associated with the purchase price of approximately 6.6 million and 9.1 million MMBtu of natural gas, respectively.
	The following table presents the current change in fair value, primarily recovered through rates from customers, associated with NU's derivative contracts not designated as hedges:
				Amounts Recognized on Derivatives
				For the Three Months Ended June 30,							For the Six Months Ended June 30,
(Millions of Dollars)			2014			2013				2014			2013
NU
Balance Sheets:
	Regulatory Assets and Liabilities		$	111.6		$	22.2			$	166		$	50.1
Statements of Income:
	Purchased Power, Fuel and Transmission			-			0.5				-			0.8
Credit Risk
Certain of NU's derivative contracts contain credit risk contingent features. These features require NU to maintain investment grade credit ratings from the major rating agencies and to post collateral for contracts in a net liability position over specified credit limits. As of June 30, 2014, NSTAR Gas had derivative contracts in a net liability position that were subject to credit risk contingent features. If NSTAR Gas' credit rating was downgraded below investment grade, NU would have been required to post approximately $0.6 million in collateral. As of December 31, 2013, there were no derivative contracts in a net liability position that were subject to credit risk contingent features.
Valuation of Derivative Instruments
Derivative contracts classified as Level 2 in the fair value hierarchy relate to the financial contracts for natural gas futures. Prices are obtained from broker quotes and are based on actual market activity. The contracts are valued using NYMEX natural gas prices. Valuations of these contracts also incorporate discount rates using the yield curve approach.
The fair value of derivative contracts classified as Level 3 utilizes significant unobservable inputs. The fair value is modeled using income techniques, such as discounted cash flow valuations adjusted for assumptions relating to exit price. Significant observable inputs for valuations of these contracts include energy and energy-related product prices in future years for which quoted prices in an active market exist. Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements. The future power and capacity prices for periods that are not quoted in an active market or established at auction are based on available market data and are escalated based on estimates of inflation to address the full time period of the contract.
Valuations of derivative contracts using a discounted cash flow methodology include assumptions regarding the timing and likelihood of scheduled payments and also reflect non-performance risk, including credit, using the default probability approach based on the counterparty's credit rating for assets and the Company's credit rating for liabilities. Valuations incorporate estimates of premiums or discounts that would be required by a market participant to arrive at an exit price, using historical market transactions adjusted for the terms of the contract.
The following is a summary of NU's, including CL&P's and NSTAR Electric's, Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts:
	As of June 30, 2014									As of December 31, 2013
		Range						Period Covered			Range					Period Covered
Energy Prices:
NU	$	63	-	66	per MWh			2018 - 2020		$	49	-	77	per MWh		2018 - 2029
CL&P	$	63	-	66	per MWh			2018 - 2020		$	56	-	58	per MWh		2018 - 2029
Capacity Prices:
NU	$	3.13	-	13		per kW-Month		2016 - 2026		$	5.07	-	11.82		per kW-Month	2017 - 2029
CL&P	$	7	-	13		per kW-Month		2018 - 2026		$	5.07	-	10.42		per kW-Month	2017 - 2026
NSTAR Electric	$	3.13	-	11.13		per kW-Month		2016 - 2019		$	5.07	-	7.38		per kW-Month	2017 - 2019
Forward Reserve:
NU, CL&P	$	3.3	-	9.5		per kW-Month		2014 - 2024		$	3.3	-	3.3		per kW-Month	2014 - 2024
REC Prices:
NU	$	38	-	70	per REC			2014 - 2018		$	36	-	87	per REC		2014 - 2029
NSTAR Electric	$	38	-	70	per REC			2014 - 2018		$	36	-	70	per REC		2014 - 2018
Exit price premiums of 8 percent through 25 percent are also applied on these contracts and reflect the most recent market activity available for similar type contracts.
Significant increases or decreases in future energy or capacity prices in isolation would decrease or increase, respectively, the fair value of the derivative liability. Any increases in the risk premiums would increase the fair value of the derivative liabilities. Changes in these fair values are recorded as a regulatory asset or liability and would not impact net income.
Valuations using significant unobservable inputs: The following tables present changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis.
		For the Three Months Ended June 30,						For the Six Months Ended June 30,
		2014			2013			2014			2013
(Millions of Dollars)		NU			NU			NU			NU
Derivatives, Net:
Fair Value as of Beginning of Period		$	-564.3		$	-833.1		$	-635.2		$	-878.6
Net Realized/Unrealized Gains Included in:
	Net Income		-			1.3			-			7.1
	Regulatory Assets and Liabilities		111.8			22.7			161.3			48.9
Settlements			21.6			21			43			34.5
Fair Value as of End of Period		$	-430.9		$	-788.1		$	-430.9		$	-788.1
		For the Three Months Ended June 30,
		2014							2013
(Millions of Dollars)		CL&P			NSTAR Electric				CL&P			NSTAR Electric
Derivatives, Net:
Fair Value as of Beginning of Period		$	-557		$	-7.3			$	-819.6		$	-13.6
Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities			112.2			-0.4				21.9			-0.5
Settlements			20.2			1.4				21.9			1
Fair Value as of End of Period		$	-424.6		$	-6.3			$	-775.8		$	-13.1
		For the Six Months Ended June 30,
		2014							2013
(Millions of Dollars)		CL&P			NSTAR Electric				CL&P			NSTAR Electric
Derivatives, Net:
Fair Value as of Beginning of Period		$	-630.6		$	-7.3			$	-866.2		$	-14.9
Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities			164.5			-0.5				46.3			0.2
Settlements			41.5			1.5				44.1			1.6
Fair Value as of End of Period		$	-424.6		$	-6.3			$	-775.8		$	-13.1

MARKETABLE_SECURITIES

MARKETABLE SECURITIES	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Marketable Securities [Text Block]	'
	5.       MARKETABLE SECURITIES
	NU maintains trusts to fund certain non-qualified executive benefits and WMECO maintains a spent nuclear fuel trust to fund WMECO's prior period spent nuclear fuel liability. These trusts hold marketable securities. These trusts are not subject to regulatory oversight by state or federal agencies. In addition, CYAPC and YAEC maintain legally restricted trusts, each of which holds marketable securities, for settling the decommissioning obligations of their nuclear power plants.
	In accordance with applicable accounting guidance, the Company elected to record mutual funds designated as available-for-sale at fair value and certain other equity investments as trading securities, with the changes in fair values recorded in Other Income, Net on the statements of income. As of June 30, 2014, the mutual funds and equity investments were classified as Level 1 in the fair value hierarchy and totaled $59.6 million and $24.9 million, respectively. As of December 31, 2013, the mutual funds were classified as Level 1, and totaled $57.2 million. Net gains on the mutual funds were $2.2 million and $0.1 million for the three months ended June 30, 2014 and 2013, respectively, and $2.4 million and $4.3 million for the six months ended June 30, 2014 and 2013, respectively. Net gains on the equity investments were $0.9 million and $1.4 million for the three and six months ended June 30, 2014, respectively. Dividend income is recorded in Other Income, Net on the statements of income when dividends are declared. All other marketable securities are accounted for as available-for-sale.
	Available-for-Sale Securities: The following is a summary of NU's and WMECO's available-for-sale securities. These securities are recorded at fair value and included in current and long-term Marketable Securities on the balance sheets.
			As of June 30, 2014
						Pre-Tax			Pre-Tax
			Amortized			Unrealized			Unrealized
	(Millions of Dollars)		Cost			Gains			Losses			Fair Value
	NU
		Debt Securities (1)	$	308.3		$	7.3		$	-0.3		$	315.3
		Equity Securities (1)		163.5			66.7			-			230.2
	WMECO
		Debt Securities (2)		58			-			-			58
			As of December 31, 2013
						Pre-Tax			Pre-Tax
			Amortized			Unrealized			Unrealized
	(Millions of Dollars)		Cost			Gains			Losses			Fair Value
	NU
		Debt Securities (1)	$	299.2		$	2.5		$	-2.1		$	299.6
		Equity Securities (1)		163.6			60.5			-			224.1
	WMECO
		Debt Securities (2)		57.9			-			-			57.9
	(1)       NU's amounts include CYAPC's and YAEC's marketable securities held in nuclear decommissioning trusts of $444.3 million and $424 million as of June 30, 2014 and December 31, 2013, respectively, the majority of which are legally restricted and can only be used for the decommissioning of the nuclear power plants owned by these companies. Unrealized gains and losses for the nuclear decommissioning trusts are offset in Other Long-Term Liabilities on the balance sheets, with no impact on the statements of income. All of the equity securities accounted for as available-for-sale securities are held in the CYAPC and YAEC trusts.
	Unrealized gains and losses on debt securities held by WMECO are recorded in Other Long-Term Assets on the balance sheets.
	Unrealized Losses and Other-than-Temporary Impairment: There have been no significant unrealized losses, other-than-temporary impairments or credit losses for NU or WMECO. Factors considered in determining whether a credit loss exists include the duration and severity of the impairment, adverse conditions specifically affecting the issuer, and the payment history, ratings and rating changes of the security. For asset-backed debt securities, underlying collateral and expected future cash flows are also evaluated.
	Realized Gains and Losses: Realized gains and losses on available-for-sale securities are recorded in Other Income, Net for NU's benefit trust, Other Long-Term Assets for WMECO, and offset in Other Long-Term Liabilities for CYAPC and YAEC. NU utilizes the specific identification basis method for the NU benefit trust and the average cost basis method for the WMECO trust and the CYAPC and YAEC nuclear decommissioning trusts to compute the realized gains and losses on the sale of available-for-sale securities.
	Contractual Maturities: As of June 30, 2014, the contractual maturities of available-for-sale debt securities are as follows:
			NU						WMECO
			Amortized						Amortized
	(Millions of Dollars)		Cost			Fair Value			Cost			Fair Value
	Less than one year (1)		$	75.9		$	75.8		$	19.2		$	19.2
	One to five years			73.9			74.6			31.9			32
	Six to ten years			56.1			57.7			2.7			2.7
	Greater than ten years			102.4			107.2			4.2			4.1
	Total Debt Securities		$	308.3		$	315.3		$	58		$	58
	(1)       Amounts in the Less than one year NU category include securities in the CYAPC and YAEC nuclear decommissioning trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets.
	Fair Value Measurements: The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy:
					NU						WMECO
					As of						As of
	(Millions of Dollars)				30-Jun-14			31-Dec-13			30-Jun-14			31-Dec-13
	Level 1:
		Mutual Funds and Equities			$	314.7		$	281.3		$	-		$	-
		Money Market Funds				42.3			32.9			2			10.9
	Total Level 1				$	357		$	314.2		$	2		$	10.9
	Level 2:
		U.S. Government Issued Debt Securities (Agency and Treasury)			$	40.6		$	61.4		$	-		$	6.8
		Corporate Debt Securities				61.8			53.6			15.8			15.1
		Asset-Backed Debt Securities				36.5			30.4			15.2			9
		Municipal Bonds				109.5			105.5			11.7			11.2
		Other Fixed Income Securities				24.6			15.8			13.3			4.9
	Total Level 2				$	273		$	266.7		$	56		$	47
	Total Marketable Securities				$	630		$	580.9		$	58		$	57.9
	U.S. government issued debt securities are valued using market approaches that incorporate transactions for the same or similar bonds and adjustments for yields and maturity dates. Corporate debt securities are valued using a market approach, utilizing recent trades of the same or similar instrument and also incorporating yield curves, credit spreads and specific bond terms and conditions. Asset-backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset-backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates and tranche information. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.

SHORT_TERM_AND_LONG_TERM_DEBT

SHORT TERM AND LONG TERM DEBT	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Debt Disclosure	'
	6.       SHORT-TERM AND LONG-TERM DEBT
	Credit Agreements and Commercial Paper Programs: Effective July 23, 2014, NU parent, CL&P, PSNH, WMECO, NSTAR Gas and Yankee Gas amended their joint $1.45 billion revolving credit facility to extend the expiration date an additional year to September 6, 2019. The revolving credit facility is to be used primarily to backstop NU parent's $1.45 billion commercial paper program. The commercial paper program allows NU parent to issue commercial paper as a form of short-term debt. As of June 30, 2014 and December 31, 2013, NU had $710.5 million and $1.01 billion, respectively, in short-term borrowings outstanding under the NU parent commercial paper program, leaving $739.5 million and $435.5 million of available borrowing capacity as of June 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of June 30, 2014 and December 31, 2013 was 0.25 percent and 0.24 percent, respectively, which is generally based on A2/P2 rated commercial paper. As of June 30, 2014, there were intercompany loans from NU of $6.4 million to CL&P, $95 million to PSNH and $15.9 million to WMECO. As of December 31, 2013, there were intercompany loans from NU of $287.3 million to CL&P and $86.5 million to PSNH.
	Effective July 23, 2014, NSTAR Electric amended its $450 million revolving credit facility to extend the expiration date an additional year to September 6, 2019. This facility serves to backstop NSTAR Electric's existing $450 million commercial paper program. As of June 30, 2014 and December 31, 2013, NSTAR Electric had $194.5 million and $103.5 million, respectively, in short-term borrowings outstanding under its commercial paper program, leaving $255.5 million and $346.5 million of available borrowing capacity as of June 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of June 30, 2014 and December 31, 2013 was 0.16 percent and 0.13 percent, respectively, which is generally based on A2/P1 rated commercial paper.
	Amounts outstanding under the commercial paper programs are generally included in Notes Payable for NU and NSTAR Electric and classified in current liabilities on the balance sheets as all borrowings are outstanding for no more than 364 days at one time. Intercompany loans from NU to CL&P, PSNH and WMECO are included in Notes Payable to NU Parent and classified in current liabilities on the balance sheets. See the Long-Term Debt portion of this Note immediately below for further information on the Yankee Gas $100 million bond issuance and its impact on the NU balance sheet as of December 31, 2013.
	Short-Term Borrowing Limits: The amount of short-term borrowings that may be incurred by NSTAR Electric is subject to periodic approval by the FERC. On June 11, 2014, the FERC granted authorization to allow NSTAR Electric to issue total short-term debt securities in an aggregate principal amount not to exceed $655 million outstanding at any one time, effective October 24, 2014 through October 23, 2016.
	Long-Term Debt: On January 2, 2014, Yankee Gas issued $100 million of 4.82 percent Series L First Mortgage Bonds, due to mature in 2044. The proceeds, net of issuance costs, were used to repay the $75 million 4.80 percent Series G First Mortgage Bonds that matured on January 1, 2014 and to pay $25 million in short-term borrowings. In accordance with applicable accounting guidance, these amounts were classified as Long-Term Debt on NU's balance sheet as of December 31, 2013.
	On March 7, 2014, NSTAR Electric issued $300 million of 4.40 percent debentures, due to mature in 2044. The proceeds, net of issuance costs, were used to repay the $300 million of 4.875 percent debentures that matured on April 15, 2014.
	On April 24, 2014, CL&P issued $250 million of 4.30 percent 2014 Series A First Mortgage Bonds, due to mature in April 2044. The proceeds, net of issuance costs, were used to repay short-term borrowings.
	On July 15, 2014, PSNH repaid at maturity the $50 million of 5.25 percent Series L First Mortgage Bonds using short-term debt.
	Working Capital: Each of NU, CL&P, NSTAR Electric, PSNH and WMECO use its available capital resources to fund its respective construction expenditures, meet debt requirements, pay operating costs, including storm-related costs, pay dividends and fund other corporate obligations, such as pension contributions. The current growth in NU's transmission construction expenditures utilizes a significant amount of cash for projects that have a long-term return on investment and recovery period. In addition, NU's Regulated companies recover their electric and natural gas distribution construction expenditures as the related project costs are depreciated over the life of the assets. This impacts the timing of the revenue stream designed to fully recover the total investment plus a return on the equity portion of the cost and related financing costs. These factors have resulted in current liabilities exceeding current assets by approximately $730 million, $220 million and $200 million at NU, CL&P and NSTAR Electric, respectively, as of June 30, 2014.
	As of June 30, 2014, $366.7 million of NU's obligations classified as current liabilities relates to long-term debt that will be paid in the next 12 months, consisting of $312 million for CL&P, $4.7 million at NSTAR Electric and $50 million for PSNH. In addition, $28.9 million relates to the amortization of the purchase accounting fair value adjustment that will be amortized in the next twelve months. NU, with its strong credit ratings, has several options available in the financial markets to repay or refinance these maturities with the issuance of new long-term debt. NU, CL&P, NSTAR Electric, PSNH and WMECO will reduce their short-term borrowings with cash received from operating cash flows or with the issuance of new long-term debt, determined considering capital requirements and maintenance of NU's credit rating and profile. Management expects the future operating cash flows of NU, CL&P, NSTAR Electric, PSNH and WMECO, along with the access to financial markets, will be sufficient to meet any future operating requirements and capital investment forecasted opportunities.

PENSION_BENEFITS_AND_POSTRETIR

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Pension and Other Postretirement Benefits Disclosure [Text Block]	'
	7.       Pension Benefits and Postretirement Benefits Other than Pensions
	The components of net periodic benefit expense for the Pension, SERP and PBOP Plans are detailed below. The net periodic benefit expense less the capitalized portion of pension and PBOP amounts is included in Operations and Maintenance on the statements of income. Capitalized pension and PBOP amounts relate to employees working on capital projects and are included in Property, Plant and Equipment, Net. Intercompany allocations are not included in the CL&P, NSTAR Electric, PSNH and WMECO net periodic benefit expense amounts.
		Pension and SERP				Pension and SERP
		For the Three Months Ended				For the Six Months Ended
		30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	19.1	$	24.6	$	41.5	$	51.1
	Interest Cost		56.3		51.9		113		103.5
	Expected Return on Plan Assets		-77.7		-68.6		-155.4		-139
	Actuarial Loss		31.7		52.6		64.7		105.5
	Prior Service Cost		1.1		1		2.1		2.1
	Total Net Periodic Benefit Expense	$	30.5	$	61.5	$	65.9	$	123.2
	Capitalized Pension Expense	$	8.7	$	19.9	$	18.4	$	36.6
		PBOP				PBOP
		For the Three Months Ended				For the Six Months Ended
		30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	3.2	$	3.7	$	6.3	$	8.5
	Interest Cost		12.1		10.9		24.7		23.6
	Expected Return on Plan Assets		-15.8		-13.9		-31.6		-27.7
	Actuarial Loss		3		4.7		6		13
	Prior Service Credit		-0.7		-0.5		-1.4		-1.1
	Total Net Periodic Benefit Expense	$	1.8	$	4.9	$	4	$	16.3
	Capitalized PBOP Expense	$	0.4	$	1.5	$	0.8	$	5
		Pension and SERP
		For the Three Months Ended June 30, 2014								For the Three Months Ended June 30, 2013
				NSTAR								NSTAR
	(Millions of Dollars)	CL&P		Electric		PSNH		WMECO		CL&P		Electric(1)		PSNH		WMECO
	Service Cost	$	5	$	3	$	2.3	$	0.8	$	6.3	$	7.3	$	3.2	$	1.2
	Interest Cost		12.4		10.3		5.8		2.5		12.1		14.7		5.9		2.5
	Expected Return on Plan Assets		-18.7		-15.7		-9.3		-4.4		-18.4		-20.2		-9.2		-4.4
	Actuarial Loss		8.2		5.9		2.8		1.7		13.9		14.6		5.4		2.9
	Prior Service Cost/(Credit)		0.5		-		0.1		0.1		0.5		-0.1		0.1		0.1
	Total Net Periodic Benefit Expense	$	7.4	$	3.5	$	1.7	$	0.7	$	14.4	$	16.3	$	5.4	$	2.3
	Intercompany Allocations	$	7.5	$	1.4	$	2.1	$	1.4	$	11.3	$	-2.2	$	2.6	$	2
	Capitalized Pension Expense	$	4.4	$	1	$	0.8	$	0.6	$	7	$	6.5	$	1.7	$	1.3
		Pension and SERP
		For the Six Months Ended June 30, 2014								For the Six Months Ended June 30, 2013
				NSTAR								NSTAR
	(Millions of Dollars)	CL&P		Electric		PSNH		WMECO		CL&P		Electric(1)		PSNH		WMECO
	Service Cost	$	10.2	$	7.6	$	5.1	$	1.9	$	12.4	$	16.5	$	6.5	$	2.4
	Interest Cost		25.7		20.6		12.3		5.2		24.2		29		11.9		5
	Expected Return on Plan Assets		-38		-31.5		-19.5		-9		-36.9		-42.2		-16.8		-8.7
	Actuarial Loss		17.3		11.7		6		3.5		28		29.1		10.8		5.9
	Prior Service Cost/(Credit)		0.9		-		0.3		0.2		0.9		-0.1		0.3		0.2
	Total Net Periodic Benefit Expense	$	16.1	$	8.4	$	4.2	$	1.8	$	28.6	$	32.3	$	12.7	$	4.8
	Intercompany Allocations	$	14.3	$	3.8	$	4.2	$	2.7	$	22.1	$	-4.1	$	5.2	$	4
	Capitalized Pension Expense	$	9.3	$	2.9	$	1.7	$	1.4	$	14	$	11.8	$	3.9	$	2.6
		PBOP
		For the Three Months Ended June 30, 2014								For the Three Months Ended June 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	0.5	$	0.8	$	0.3	$	0.1	$	0.9	$	0.6	$	0.2
	Interest Cost		1.9		4.8		1		0.4		2		1		0.4
	Expected Return on Plan Assets		-2.5		-6.5		-1.3		-0.6		-2.5		-1.3		-0.6
	Actuarial Loss/(Gain)		1		-0.2		0.6		0.1		1.9		0.9		0.3
	Prior Service Credit		-		-0.5		-		-		-		-		-
	Total Net Periodic Benefit Expense/(Income)	$	0.9	$	-1.6	$	0.6	$	0	$	2.3	$	1.2	$	0.3
	Intercompany Allocations	$	1.1	$	-	$	0.3	$	0.2	$	1.9	$	0.4	$	0.3
	Capitalized PBOP Expense/(Income)	$	0.5	$	-0.5	$	0.2	$	-	$	1.2	$	0.4	$	0.2
		PBOP
		For the Six Months Ended June 30, 2014								For the Six Months Ended June 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	1.1	$	1.6	$	0.7	$	0.2	$	1.7	$	1.1	$	0.4
Interest Cost		4		9.7		2.1		0.8		3.9		2		0.8
Expected Return on Plan Assets		-5.2		-13		-2.7		-1.1		-5		-2.6		-1.2
Actuarial Loss/(Gain)		2.1		-0.3		1.1		0.2		3.7		1.8		0.6
Prior Service Credit		-		-0.9		-		-		-		-		-
Total Net Periodic Benefit Expense/(Income)	$	2	$	-2.9	$	1.2	$	0.1	$	4.3	$	2.3	$	0.6
Intercompany Allocations	$	2.2	$	0.1	$	0.6	$	0.4	$	3.6	$	0.8	$	0.6
Capitalized PBOP Expense/(Income)	$	1	$	-1	$	0.4	$	0.1	$	2.4	$	0.7	$	0.4
NSTAR Electric's pension amounts for the three and six months ended June 30, 2013 do not include SERP expense.
For the three and six months ended June 30, 2013, the net periodic PBOP expense allocated to NSTAR Electric was a benefit of $2 million and an expense of $2.3 million, respectively.
As of December 31, 2013, the funded status of the NSTAR Pension Plan was recorded on NSTAR Electric's balance sheet while the total SERP obligation and PBOP Plan funded status were recorded on NSTAR Electric & Gas' balance sheet. As of December 31, 2013, all NSTAR employees were employed by NSTAR Electric & Gas. On January 1, 2014, NSTAR Electric & Gas was merged into NUSCO and, concurrently, all employees were transferred to the company they predominately provide services for: NUSCO, NSTAR Electric or NSTAR Gas. As a result of the employee transfers, the pension and PBOP assets and liabilities were attributed by participant and transferred to the respective company's balance sheets.
As of June 30, 2014, the liabilities associated with the Pension, SERP and PBOP plans for NSTAR Electric were $85.8 million for the Pension Plan, $3.6 million for the SERP Plans ($0.4 million of which is included in other current liabilities) and $61.2 million for the PBOP Plan. As of December 31, 2013, the liability associated with the NSTAR Pension Plan for NSTAR Electric was $118 million. This change had no impact on the income statement or net assets of NSTAR Electric or NU.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Commitments and Contingencies Disclosure [Text Block]	'
	8.       COMMITMENTS AND CONTINGENCIES
	A.       Environmental Matters
	General: NU, CL&P, NSTAR Electric, PSNH and WMECO are subject to environmental laws and regulations intended to mitigate or remove the effect of past operations and improve or maintain the quality of the environment. These laws and regulations require the removal or the remedy of the effect on the environment of the disposal or release of certain specified hazardous substances at current and former operating sites. NU, CL&P, NSTAR Electric, PSNH and WMECO have an active environmental auditing and training program and believe that they are substantially in compliance with all enacted laws and regulations.
	The number of environmental sites and reserves related to these sites for which remediation or long-term monitoring, preliminary site work or site assessment are being performed are as follows:
		As of June 30, 2014					As of December 31, 2013
				Reserve						Reserve
		Number of Sites		(in millions)			Number of Sites			(in millions)
	NU		66	$	34.5			68		$	35.4
	CL&P		17		4.2			18			3.4
	NSTAR Electric		14		1.2			12			1.2
	PSNH		13		5.3			15			5.4
	WMECO		5		0.6			5			0.4
	Included in the NU number of sites and reserve amounts above are former MGP sites that were operated several decades ago and manufactured gas from coal and other processes, which resulted in certain by-products remaining in the environment that may pose a potential risk to human health and the environment. The reserve balance related to these former MGP sites was $29.8 million and $31.4 million as of June 30, 2014 and December 31, 2013, respectively, and relates primarily to the natural gas business segment.
	B.       Long-Term Contractual Arrangements
	The following is an update to the current status of long-term contractual arrangements set forth in Note 12B of the NU 2013 Form 10-K.
	Renewable Energy: Renewable energy contracts include non-cancelable commitments under contracts of NSTAR Electric and WMECO for the purchase of energy and capacity from renewable energy facilities.
		July - December
	(Millions of Dollars)	2014		2015		2016			2017			2018		Thereafter		Total
	Renewable Energy
	NSTAR Electric	$	43.6	$	86.3	$	93.7		$	89.8		$	53.3	$	302.8	$	669.5
	WMECO		-		-		2.4			2.4			2.4		28.9		36.1
	C.       Contractual Obligations – Yankee Companies
	Spent Nuclear Fuel Litigation - DOE Phase II Damages - On November 15, 2013, the Court of Federal Claims issued an award to CYAPC for $126.3 million, YAEC for $73.3 million and MYAPC for $35.8 million for lawsuits against the DOE seeking recovery of actual damages incurred in the years following 2001 and 2002 (DOE Phase II Damages). On January 14, 2014, the Yankee Companies received a letter from the U.S. Department of Justice stating that the DOE will not appeal the court's final judgment.
	On March 28, 2014, CYAPC, YAEC and MYAPC received payment of $90 million, $73.3 million and $35.8 million, respectively, of the DOE Phase II Damages proceeds. On April 24, 2014, CYAPC received payment of the remaining $36.3 million proceeds. On April 28, 2014, the Yankee Companies made the required informational filing with FERC in accordance with the process and methodology outlined in the 2013 FERC order. The Yankee Companies returned the DOE Phase II Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, for the benefit of their respective customers, on June 1, 2014.
	As of June 30, 2014, CL&P's refund obligation to customers of $65.4 million was recorded as an offset to the deferred storm restoration costs regulatory asset, as directed by PURA. NSTAR Electric's, PSNH's and WMECO's refund obligation to customers of $29.1 million, $13.1 million and $18.1 million, respectively, was recorded as a regulatory liability in each company's respective regulatory tracker mechanisms. For further information, see Note 2, "Regulatory Accounting," to the financial statements.
	DOE Phase III Damages - On August 15, 2013, the Yankee Companies each filed subsequent lawsuits against the DOE seeking recovery of actual damages incurred in the years 2009 through 2012. Responsive pleading from the U.S. Department of Justice was filed on November 18, 2013, and discovery has begun.
	D.       Guarantees and Indemnifications
	NU parent provides credit assurances on behalf of its subsidiaries, including CL&P, NSTAR Electric, PSNH and WMECO, in the form of guarantees in the normal course of business.
	NU provided guarantees and various indemnifications on behalf of external parties as a result of the sales of former subsidiaries of NU Enterprises and the termination of an unregulated business, with maximum exposures either not specified or not material.
	NU also issued a guaranty under which, beginning at the time the Northern Pass Transmission line goes into commercial operation, NU will guarantee the financial obligations of NPT under the TSA in an amount not to exceed $25 million. NU's obligations under the guaranty expire upon the full, final and indefeasible payment of the guaranteed obligations.
	Management does not anticipate a material impact to Net Income as a result of these various guarantees and indemnifications.
	The following table summarizes NU's guarantees of its subsidiaries, including CL&P, NSTAR Electric, PSNH and WMECO, as of June 30, 2014:
				Maximum Exposure
	Subsidiary		Description	(in millions)			Expiration Dates
	Various		Surety Bonds	$	67		2014 - 2016 (1)
	Various		New England Hydro Companies' Long-Term Debt	$	2.5		Unspecified
	NUSCO and RRR		Lease Payments for Vehicles and Real Estate	$	16		2019 and 2024
	(1)       Surety bond expiration dates reflect termination dates, the majority of which will be renewed or extended.
	Certain surety bonds contain credit ratings triggers that would require NU parent to post collateral in the event that the unsecured debt credit ratings of NU are downgraded.
	E.       FERC Base ROE Complaints
	On September 30, 2011, a complaint was filed jointly at FERC under Sections 206 and 306 of the Federal Power Act by several New England state attorneys general, state regulatory commissions, consumer advocates and other parties (the “Complainants”). The Complainants alleged that the base ROE of 11.14 percent that has been utilized since 2006 in the calculation of formula rates for transmission service under the ISO-NE Open Access Transmission Tariff by NETOs, including CL&P, NSTAR Electric, PSNH and WMECO, was unjust and unreasonable and asserted that the rate was excessive due to changes in the capital markets. Complainants sought an order to reduce the base ROE, effective October 1, 2011, and to require refunds. The FERC set the case for trial before a FERC ALJ after settlement negotiations were unsuccessful in August 2012.
	On August 6, 2013, the FERC ALJ issued an initial decision finding that the base ROE in effect from October 1, 2011 through December 31, 2012 (refund period) was not reasonable, and recommended separate base ROEs for the refund period of 10.6 percent and for the period beginning when FERC issues its final decision (prospective period) of 9.7 percent, leaving policy considerations and additional adjustments to the FERC. In the third quarter of 2013, the Company recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact from the FERC ALJ's initial decision for the refund period. The aggregate after-tax charge to third quarter 2013 earnings totaled $14.3 million at NU, which represented reserves of $7.7 million at CL&P, $3.4 million at NSTAR Electric, $1.4 million at PSNH and $1.8 million at WMECO.
	On June 19, 2014, FERC issued an order partially affirming and partially reversing the ALJ's initial decision. FERC set a single tentative base ROE of 10.57 percent for the refund period and prospective period. FERC also modified its traditional methodology by adopting a two-step discounted cash flow analysis that it utilizes to determine the ROEs of both natural gas and oil pipeline projects. Using this methodology, FERC determined a new zone of reasonableness of 7.03 percent to 11.74 percent, and set the tentative base ROE at the 75th percentile of this new zone. FERC also stated that a utility's total ROE inclusive of transmission incentive ROE adders, should not exceed the top of the new zone of reasonableness produced by this methodology. FERC instituted a paper hearing on the long-term growth rate portion of the methodology, before it issues a final determination on the base ROE. On July 21, 2014, the NETOs and Complainants filed rehearing requests in this proceeding.
	On December 27, 2012, a second complaint was filed jointly at FERC by several additional consumer groups and municipal parties, which challenged the NETOs' base ROE and sought refunds for the 15-month period beginning January 1, 2013. On June 19, 2014, the FERC issued a second order finding that the complaint raised issues of material fact, and set this complaint for trial, should settlement negotiations be unsuccessful. FERC stated that it could issue an order in this case by mid-2016. On July 21, 2014, the NETOs filed a rehearing request in this proceeding.
	Though NU cannot predict the ultimate outcome of this proceeding, in the second quarter of 2014, the Company recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact from the FERC's two orders issued on June 19, 2014 for the two refund periods. The aggregate after-tax charge to second quarter 2014 earnings totaled $32.1 million at NU, which represented reserves of $18.5 million at CL&P, $6.1 million at NSTAR Electric, $2 million at PSNH and $5.5 million at WMECO.
	As of June 30, 2014, the cumulative pre-tax reserves totaled $79.3 million at NU, $44.7 million at CL&P, $16.2 million at NSTAR Electric, $6.2 million at PSNH and $12.2 million at WMECO. As of December 31, 2013, the pre-tax reserves totaled $24.6 million at NU, $13.3 million at CL&P, $5.9 million at NSTAR Electric, $2.4 million at PSNH and $3 million at WMECO. The reserves were recorded in each electric subsidiary's respective transmission regulatory tracker mechanism and as a reduction of operating revenues. See Note 2, “Regulatory Accounting” for further information.
	On July 31, 2014, the Complainants filed an additional complaint with FERC. At this time, the Company cannot determine the outcome of this complaint.
	F.        CPSL
	Since 2006, NSTAR Electric has been recovering incremental costs related to the DPU-approved Safety and Reliability Programs. From 2006 through 2011, cumulative costs associated with the CPSL program resulted in an incremental revenue requirement to customers of approximately $83 million. These amounts included incremental operations and maintenance costs and the related revenue requirement for specific capital investments relative to the CPSL programs.
	On May 28, 2010, the DPU issued an order on NSTAR Electric's 2006 CPSL cost recovery filing (the May 2010 Order). In October 2010, NSTAR Electric filed a reconciliation of the cumulative CPSL program activity for the periods 2006 through 2009 with the DPU in order to determine a proposed rate adjustment. The DPU allowed the proposed rates to go into effect January 1, 2011, subject to final reconciliation of CPSL program costs through a future DPU proceeding. In February 2013, NSTAR Electric updated the October 2010 filing with final activity through 2011. NSTAR Electric recorded its 2006 through 2011 revenues under the CPSL programs based on the May 2010 Order.
	NSTAR Electric cannot predict the timing of a final DPU order related to its CPSL filings for the period 2006 through 2011. While management does not believe that any subsequent DPU order would result in revenues that are materially different than the amounts already recognized, it is reasonably possible that an order could have a material impact on NSTAR Electric's results of operations, financial position and cash flows.
	G.       Basic Service Bad Debt Adder
	In accordance with a generic DPU order, electric utilities in Massachusetts recover the energy-related portion of bad debt costs in their Basic Service rates. In 2007, NSTAR Electric filed its 2006 Basic Service reconciliation with the DPU proposing an adjustment related to the increase of its Basic Service bad debt charge-offs. The DPU issued an order approving the implementation of a revised Basic Service rate but instructed NSTAR Electric to reduce distribution rates by an amount equal to the increase in its Basic Service bad debt charge-offs. This adjustment to NSTAR Electric's distribution rates would eliminate the fully reconciling nature of the Basic Service bad debt adder.
	In 2010, NSTAR Electric filed an appeal of the DPU's order with the SJC. In 2012, the SJC vacated the DPU order and remanded the matter to the DPU for further review. The DPU has not taken any action on the remand.
	NSTAR Electric deferred approximately $34 million of costs associated with energy-related bad debt as a regulatory asset through 2011 as NSTAR Electric had concluded that it was probable that these costs would ultimately be recovered from customers. Due to the delays and the duration of the proceedings, NSTAR Electric concluded that while an ultimate outcome on the matter in its favor remained "more likely than not," it could no longer be deemed "probable." As a result, NSTAR Electric recognized a reserve related to the regulatory asset in 2012. NSTAR Electric will continue to maintain the reserve until the proceeding has been concluded with the DPU.

FAIR_VALUE_OF_FINANCIAL_INSTRU

FAIR VALUE OF FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Fair Value Disclosures [Text Block]	'
	9.       FAIR VALUE OF FINANCIAL INSTRUMENTS
	The following methods and assumptions were used to estimate the fair value of each of the following financial instruments:
	Preferred Stock and Long-Term Debt: The fair value of CL&P's and NSTAR Electric's preferred stock is based upon pricing models that incorporate interest rates and other market factors, valuations or trades of similar securities and cash flow projections. The fair value of fixed-rate long-term debt securities is based upon pricing models that incorporate quoted market prices for those issues or similar issues adjusted for market conditions, credit ratings of the respective companies and treasury benchmark yields. Adjustable rate long-term debt securities are assumed to have a fair value equal to their carrying value. The fair values provided in the tables below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows:
		As of June 30, 2014				As of December 31, 2013
		NU				NU
		Carrying		Fair		Carrying		Fair
	(Millions of Dollars)	Amount		Value		Amount		Value
	Preferred Stock Not Subject to Mandatory Redemption	$	155.6	$	150.1	$	155.6	$	152.7
	Long-Term Debt		8,542.70		9,008.40		8,310.20		8,443.10
		As of June 30, 2014
		CL&P				NSTAR Electric				PSNH				WMECO
		Carrying		Fair		Carrying		Fair		Carrying		Fair		Carrying		Fair
	(Millions of Dollars)	Amount		Value		Amount		Value		Amount		Value		Amount		Value
	Preferred Stock Not Subject to Mandatory Redemption	$	116.2	$	110.3	$	43	$	39.8	$	-	$	-	$	-	$	-
	Long-Term Debt		2,991.60		3,344.50		1,797.40		1,949.80		1,049.20		1,105.80		628.9		665.3
		As of December 31, 2013
		CL&P				NSTAR Electric				PSNH				WMECO
		Carrying		Fair		Carrying		Fair		Carrying		Fair		Carrying		Fair
	(Millions of Dollars)	Amount		Value		Amount		Value		Amount		Value		Amount		Value
	Preferred Stock Not Subject to Mandatory Redemption	$	116.2	$	110.5	$	43	$	42.2	$	-	$	-	$	-	$	-
	Long-Term Debt		2,741.20		2,952.80		1,801.10		1,888.00		1,049.00		1,073.90		629.4		640.1
	Derivative Instruments: Derivative instruments are carried at fair value. For further information, see Note 4, "Derivative Instruments," to the financial statements.
	Other Financial Instruments: Investments in marketable securities are carried at fair value. For further information, see Note 1D, "Summary of Significant Accounting Policies - Fair Value Measurements," and Note 5, "Marketable Securities," to the financial statements. The carrying value of other financial instruments included in current assets and current liabilities, including cash and cash equivalents and special deposits, approximates their fair value due to the short-term nature of these instruments.

ACCUMULATED_OTHER_COMPREHENSIV

ACCUMULATED OTHER COMPREHENSIVE INCOME	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Comprehensive Income Note [Text Block]	'
	10.       ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)
	The changes in accumulated other comprehensive income/(loss) by component, net of tax, is as follows:
			For the Six Months Ended June 30, 2014												For the Six Months Ended June 30, 2013
						Unrealized			Pension,								Unrealized		Pension,
			Qualified			Gains/(Losses)			SERP and						Qualified		Gains/(Losses)		SERP and
			Cash Flow			on Available-			PBOP						Cash Flow		on Available-		PBOP
			Hedging			for-Sale			Benefit						Hedging		for-Sale		Benefit
	(Millions of Dollars)		Instruments			Securities			Plans			Total			Instruments		Securities		Plans		Total
	AOCI as of Beginning of Period		$	-14.4		$	0.4		$	-32		$	-46		$	-16.4	$	1.3	$	-57.8	$	-72.9
	OCI Before Reclassifications			-			0.5			1.2			1.7			-		-0.7		-		-0.7
	Amounts Reclassified from AOCI			1			-			1.8			2.8			1		-		3.1		4.1
	Net OCI			1			0.5			3			4.5			1		-0.7		3.1		3.4
	AOCI as of End of Period		$	-13.4		$	0.9		$	-29		$	-41.5		$	-15.4	$	0.6	$	-54.7	$	-69.5
	NU's qualified cash flow hedging instruments represent interest rate swap agreements on debt issuances that were settled in prior years. The settlement amount was recorded in AOCI and is being amortized into Net Income over the term of the underlying debt instrument. CL&P, PSNH and WMECO continue to amortize interest rate swaps settled in prior years from AOCI into Interest Expense over the remaining life of the associated long-term debt, which are not material to their respective financial statements.
	The following table sets forth the amounts reclassified from AOCI by component and the impacted line item on the statements of income:
		For the Three Months Ended						For the Six Months Ended
		June 30,						June 30,
		Amounts Reclassified						Amounts Reclassified						Statements of Income
		from AOCI						from AOCI						Line Item Impacted
	(Millions of Dollars)	2014			2013			2014			2013
	Qualified Cash Flow Hedging Instruments	$	-0.8		$	-0.8		$	-1.7		$	-1.7		Interest Expense
	Tax Benefit		0.3			0.3			0.7			0.7		Income Tax Expense
	Qualified Cash Flow Hedging Instruments, Net of Tax	$	-0.5		$	-0.5		$	-1		$	-1
	Pension, SERP and PBOP Benefit Plan Costs:
	Amortization of Actuarial Losses	$	-1.2		$	-2.2		$	-2.9		$	-4.7		Operations and Maintenance (1)
	Amortization of Prior Service Cost		-			-			-0.1			-0.1		Operations and Maintenance (1)
	Total Pension, SERP and PBOP Benefit Plan Costs		-1.2			-2.2			-3			-4.8
	Tax Benefit		0.5			0.7			1.2			1.7		Income Tax Expense
	Pension, SERP and PBOP Benefit Plan Costs, Net of Tax	$	-0.7		$	-1.5		$	-1.8		$	-3.1
	Total Amounts Reclassified from AOCI, Net of Tax	$	-1.2		$	-2		$	-2.8		$	-4.1
	These amounts are included in the computation of net periodic Pension, SERP and PBOP costs. See Note 7, "Pension Benefits and Postretirement Benefits Other Than Pensions," for further information.

COMMON_SHARES

COMMON SHARES	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Stock by Class [Text Block]	'
	11.       COMMON SHARES
	The following table sets forth the NU common shares and the shares of common stock of CL&P, NSTAR Electric, PSNH and WMECO that were authorized and issued and the respective per share par values:
		Shares
				Authorized as of
		Per Share		June 30, 2014 and	Issued as of
		Par Value		31-Dec-13	30-Jun-14	31-Dec-13
	NU	$	5	380,000,000	333,327,485	333,113,492
	CL&P	$	10	24,500,000	6,035,205	6,035,205
	NSTAR Electric	$	1	100,000,000	100	100
	PSNH	$	1	100,000,000	301	301
	WMECO	$	25	1,072,471	434,653	434,653
	As of June 30, 2014 and December 31, 2013, there were 17,108,131 and 17,796,672 NU common shares held as treasury shares, respectively. As of June 30, 2014 and December 31, 2013, NU common shares outstanding were 316,219,354 and 315,273,559, respectively.

COMMON_SHARESHOLDERS_EQUITY_AN

COMMON SHARESHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (NU)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Stockholders' Equity Note Disclosure [Text Block]	'
	12	COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS
	A summary of the changes in Common Shareholders' Equity and Noncontrolling Interests of NU is as follows:
			For the Three Months Ended
			30-Jun-14				30-Jun-13
					Noncontrolling				Noncontrolling
					Interest -				Interest -
			Common		Preferred		Common		Preferred
			Shareholders'		Stock of		Shareholders'		Stock of
	(Millions of Dollars)		Equity		Subsidiaries		Equity		Subsidiaries
	Balance as of Beginning of Period		$	9,723.90	$	155.6	$	9,345.20	$	155.6
	Net Income			129.2		-		173.1		-
	Dividends on Common Shares			-124.1		-		-115.6		-
	Dividends on Preferred Stock			-1.9		-1.9		-2		-2
	Issuance of Common Shares			0.2		-		0.3		-
	Other Transactions, Net			23.7		-		4.2		-
	Net Income Attributable to Noncontrolling Interests			-		1.9		-		2
	Other Comprehensive Income			2.8		-		1.4		-
	Balance as of End of Period		$	9,753.80	$	155.6	$	9,406.60	$	155.6
			For the Six Months Ended
			30-Jun-14				30-Jun-13
					Noncontrolling				Noncontrolling
					Interest -				Interest -
			Common		Preferred		Common		Preferred
			Shareholders'		Stock of		Shareholders'		Stock of
	(Millions of Dollars)		Equity		Subsidiaries		Equity		Subsidiaries
	Balance as of Beginning of Period		$	9,611.50	$	155.6	$	9,237.10	$	155.6
	Net Income			367.1		-		403		-
	Dividends on Common Shares			-247.9		-		-232.1		-
	Dividends on Preferred Stock			-3.8		-3.8		-3.9		-3.9
	Issuance of Common Shares			5.4		-		8.8		-
	Other Transactions, Net			17		-		-9.7		-
	Net Income Attributable to Noncontrolling Interests			-		3.8		-		3.9
	Other Comprehensive Income			4.5		-		3.4		-
	Balance as of End of Period		$	9,753.80	$	155.6	$	9,406.60	$	155.6

EARNINGS_PER_SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Earnings Per Share [Text Block]	'
	13.       EARNINGS PER SHARE
	Basic EPS is computed based upon the weighted average number of common shares outstanding during each period. Diluted EPS is computed on the basis of the weighted average number of common shares outstanding plus the potential dilutive effect of certain share-based compensation awards as if they were converted into common shares. There were no antidilutive share awards outstanding for the three and six months ended June 30, 2014 or for the three months ended June 30, 2013. For the six months ended June 30, 2013, there were 3,150 antidilutive share awards excluded from the computation.
	The following table sets forth the components of basic and diluted EPS:
			For the Three Months Ended				For the Six Months Ended
	(Millions of Dollars, except share information)		30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	Net Income Attributable to Controlling Interest		$	127.4	$	171	$	363.3	$	399.1
	Weighted Average Common Shares Outstanding:
		Basic		315,950,510		315,154,130		315,742,511		315,141,956
		Dilutive Effect		1,162,291		808,489		1,259,950		840,622
		Diluted		317,112,801		315,962,619		317,002,461		315,982,578
	Basic EPS		$	0.4	$	0.54	$	1.15	$	1.27
	Diluted EPS		$	0.4	$	0.54	$	1.15	$	1.26
	RSUs and performance shares are included in basic weighted average common shares outstanding as of the date that all necessary vesting conditions have been satisfied. The dilutive effect of unvested RSUs and performance shares is calculated using the treasury stock method. Assumed proceeds of these units under the treasury stock method consist of the remaining compensation cost to be recognized and a theoretical tax benefit. The theoretical tax benefit is calculated as the tax impact of the intrinsic value of the units (the difference between the market value of the average units outstanding for the period, using the average market price during the period, and the grant date market value).
	The dilutive effect of stock options to purchase common shares is also calculated using the treasury stock method. Assumed proceeds for stock options consist of cash proceeds that would be received upon exercise, and a theoretical tax benefit. The theoretical tax benefit is calculated as the tax impact of the intrinsic value of the stock options (the difference between the market value of the average stock options outstanding for the period, using the average market price during the period, and the exercise price).

SEGMENT_INFORMATION

SEGMENT INFORMATION	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	14.       SEGMENT INFORMATION
	Presentation: NU is organized between the Electric Distribution, Electric Transmission and Natural Gas Distribution reportable segments and Other based on a combination of factors, including the characteristics of each segments' products and services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates. These reportable segments represented substantially all of NU's total consolidated revenues for the three and six months ended June 30, 2014 and 2013. Revenues from the sale of electricity and natural gas primarily are derived from residential, commercial and industrial customers and are not dependent on any single customer. The Electric Distribution reportable segment includes the generation activities of PSNH and WMECO.
	The remainder of NU's operations is presented as Other in the tables below and primarily consists of 1) the equity in earnings of NU parent from its subsidiaries and intercompany interest income, both of which are eliminated in consolidation, and interest expense related to the debt of NU parent, 2) the revenues and expenses of NU's service company, most of which are eliminated in consolidation, 3) the operations of CYAPC and YAEC, and 4) the results of other non-regulated subsidiaries, which are not part of its core business.
	Cash flows used for investments in plant included in the segment information below are cash capital expenditures that do not include amounts incurred but not paid, cost of removal, AFUDC related to equity funds, and the capitalized portions of pension expense.
	NU's reportable segments are determined based upon the level at which NU's chief operating decision maker assesses performance and makes decisions about the allocation of company resources. Each of NU's subsidiaries, including CL&P, NSTAR Electric, PSNH and WMECO, has one reportable segment. NU's operating segments and reporting units are consistent with its reportable business segments.
	NU's segment information is as follows:
		For the Three Months Ended June 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,261.80	$	195.5	$	206.9	$	184.7	$	-171.3	$	1,677.60
	Depreciation and Amortization		-89.3		-16.9		-37		-7.7		2.3		-148.6
	Other Operating Expenses		-991.5		-166.5		-71		-174.9		168.9		-1,235.00
	Operating Income		181		12.1		98.9		2.1		-0.1		294
	Interest Expense		-47.2		-8.7		-28.8		-9.1		1.3		-92.5
	Other Income, Net		2.9		-		2.7		137.7		-137.8		5.5
	Net Income Attributable to Controlling Interest	$	83.4	$	2	$	43.9	$	133.3	$	-135.2	$	127.4
		For the Six Months Ended June 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	2,847.80	$	628.3	$	458.9	$	356.9	$	-323.7	$	3,968.20
	Depreciation and Amortization		-238.2		-34.6		-74		-14.7		4.1		-357.4
	Other Operating Expenses		-2,202.40		-487.9		-137.3		-340.3		318.8		-2,849.10
	Operating Income		407.2		105.8		247.6		1.9		-0.8		761.7
	Interest Expense		-94.6		-17.1		-54.3		-18.7		2.2		-182.5
	Other Income, Net		4.3		0.1		4.2		432.4		-433.8		7.2
	Net Income Attributable to Controlling Interest	$	195.6	$	54.1	$	118.8	$	424.9	$	-430.1	$	363.3
	Cash Flows Used for Investments in Plant	$	335.6	$	68.6	$	289.3	$	30.5	$	-	$	724
		For the Three Months Ended June 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,221.60	$	154.1	$	247.9	$	220.7	$	-208.4	$	1,635.90
	Depreciation and Amortization		-152.2		-16.7		-34.5		-21.7		2.9		-222.2
	Other Operating Expenses		-883.3		-127		-63.6		-194.9		205.7		-1,063.10
	Operating Income		186.1		10.4		149.8		4.1		0.2		350.6
	Interest Expense		-43.4		-8.9		-25.2		-10.7		1.3		-86.9
	Other Income, Net		2.2		0.1		2.8		232.2		-232.3		5
	Net Income Attributable to Controlling Interest	$	91.2	$	1.2	$	76.8	$	232.8	$	-231	$	171
		For the Six Months Ended June 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	2,595.80	$	515.9	$	487.4	$	437.8	$	-406	$	3,630.90
	Depreciation and Amortization		-329.1		-34.1		-66.3		-40.8		4.6		-465.7
	Other Operating Expenses		-1,888.30		-394.3		-125.8		-392.2		404.9		-2,395.70
	Operating Income		378.4		87.5		295.3		4.8		3.5		769.5
	Interest Expense		-85.6		-16.2		-47.1		-17.1		2.9		-163.1
	Other Income, Net		7.1		0.3		5.5		554		-554.2		12.7
	Net Income Attributable to Controlling Interest	$	190.6	$	44.5	$	156.7	$	555.5	$	-548.2	$	399.1
	Cash Flows Used for Investments in Plant	$	315.3	$	70.9	$	297.4	$	16.7	$	-	$	700.3
	The following table summarizes NU's segmented total assets:
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	As of June 30, 2014	$	16,942.50	$	2,753.80	$	6,934.10	$	11,566.60	$	-10,406.60	$	27,790.40
	As of December 31, 2013		17,260.00		2,759.70		6,745.80		11,842.40		-10,812.40		27,795.50

SIGNIFCANT_ACCOUNTING_POLICIES

SIGNIFCANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Organization Consolidation And Presentation Of Financial Statements Disclosure Text Block	'
	A.       Basis of Presentation
	NU is a public utility holding company primarily engaged through its wholly owned regulated utility subsidiaries in the energy delivery business. NU's wholly owned regulated utility subsidiaries consist of CL&P, NSTAR Electric, PSNH, WMECO, Yankee Gas and NSTAR Gas. NU provides energy delivery service to approximately 3.6 million electric and natural gas customers through these six regulated utilities in Connecticut, Massachusetts and New Hampshire.
	The unaudited condensed consolidated financial statements of NU, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements of NU, NSTAR Electric and PSNH and the unaudited condensed financial statements of CL&P and WMECO are herein collectively referred to as the "financial statements."
	The combined notes to the financial statements have been prepared pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures included in annual financial statements prepared in accordance with GAAP have been omitted pursuant to such rules and regulations. The accompanying financial statements should be read in conjunction with the entirety of this combined Quarterly Report on Form 10-Q, the first quarter 2014 combined Quarterly Report on Form 10-Q and the 2013 combined Annual Report on Form 10-K of NU, CL&P, NSTAR Electric, PSNH and WMECO, which were filed with the SEC. The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	The financial statements contain, in the opinion of management, all adjustments (including normal, recurring adjustments) necessary to present fairly NU's, CL&P's, NSTAR Electric's, PSNH's and WMECO's financial position as of June 30, 2014 and December 31, 2013, the results of operations and comprehensive income for the three and six months ended June 30, 2014 and 2013, and the cash flows for the six months ended June 30, 2014 and 2013. The results of operations and comprehensive income for the three and six months ended June 30, 2014 and 2013, and the cash flows for the six months ended June 30, 2014 and 2013 are not necessarily indicative of the results expected for a full year. The demand for electricity and natural gas is affected by weather conditions, economic conditions, and consumer conservation (including company-sponsored energy efficiency programs). Electric energy sales and revenues are typically higher in the winter and summer months than in the spring and fall months. Natural gas sales and revenues are typically higher in the winter months than during other periods of the year.
	NU consolidates CYAPC and YAEC as CL&P's, NSTAR Electric's, PSNH's and WMECO's combined ownership interest in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and WMECO and the CYAPC and YAEC companies have been eliminated in consolidation of the NU financial statements. For CL&P, NSTAR Electric, PSNH and WMECO, the investments in CYAPC and YAEC continue to be accounted for under the equity method.
	NU's utility subsidiaries are subject to the application of accounting guidance for entities with rate-regulated operations that considers the effect of regulation resulting from differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. NU's utility subsidiaries' energy delivery business is subject to rate-regulation that is based on cost recovery and meets the criteria for application of rate-regulated accounting. See Note 2, "Regulatory Accounting," for further information.
	Certain reclassifications of prior period data were made in the accompanying balance sheets for NU, CL&P, NSTAR Electric and PSNH, and in the statements of income for NU, NSTAR Electric, PSNH and WMECO. These reclassifications were made to conform to the current period presentation.
Receivables Policy Text Block	'
	NU, including CL&P, NSTAR Electric, PSNH and WMECO, presents its receivables at estimated net realizable value by maintaining a provision for uncollectible accounts. This provision is determined based upon a variety of factors, including the application of an estimated uncollectible percentage to each receivable aging category. The estimate is based upon historical collection and write-off experience and management's assessment of collectibility from individual customers. Management continuously assesses the collectibility of receivables, and adjusts collectibility estimates based on actual experience. Receivable balances are written off against the provision for uncollectible accounts when the accounts are terminated and these balances are deemed to be uncollectible.
Fair Value Of Financial Instruments Policy	'
	Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases or normal sales" (normal) and to the marketable securities held in trusts. Fair value measurement guidance is also applied to investment valuations used to calculate the funded status of pension and PBOP plans and nonrecurring fair value measurements of nonfinancial assets such as goodwill and AROs.
	Fair Value Hierarchy: In measuring fair value, NU uses observable market data when available and minimizes the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. NU evaluates the classification of assets and liabilities measured at fair value on a quarterly basis, and NU's policy is to recognize transfers between levels of the fair value hierarchy as of the end of the reporting period. The three levels of the fair value hierarchy are described below:
	Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date.  Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable.
	Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products.
	The following methods and assumptions were used to estimate the fair value of each of the following financial instruments:
	Preferred Stock and Long-Term Debt: The fair value of CL&P's and NSTAR Electric's preferred stock is based upon pricing models that incorporate interest rates and other market factors, valuations or trades of similar securities and cash flow projections. The fair value of fixed-rate long-term debt securities is based upon pricing models that incorporate quoted market prices for those issues or similar issues adjusted for market conditions, credit ratings of the respective companies and treasury benchmark yields. Adjustable rate long-term debt securities are assumed to have a fair value equal to their carrying value. The fair values provided in the tables below are classified as Level 2 within the fair value hierarchy.
Other Taxes Policy	'Gross receipts taxes levied by the state of Connecticut are collected by CL&P and Yankee Gas from their respective customers. These gross receipts taxes are shown on a gross basis with collections in Operating Revenues and payments in Taxes Other Than Income Taxes on the statements of income Certain sales taxes are also collected by NU's companies that serve customers in Connecticut and Massachusetts as agents for state and local governments and are recorded on a net basis with no impact on the statements of income.
Public Utilities Policy Text Block	'
	The rates charged to the customers of NU's Regulated companies are designed to collect each company's costs to provide service, including a return on investment. Therefore, the accounting policies of the Regulated companies follow the application of accounting guidance for entities with rate-regulated operations and reflect the effects of the rate-making process.
	Management believes it is probable that each of the Regulated companies will recover their respective investments in long-lived assets, including regulatory assets. If management were to determine that it could no longer apply the accounting guidance applicable to rate-regulated enterprises to any of the Regulated companies' operations, or that management could not conclude it is probable that costs would be recovered from customers in future rates, the costs would be charged to net income in the period in which the determination is made.
Derivatives Policy Text Block	'
	4.       DERIVATIVE INSTRUMENTS
Marketable Securities Policy	'
	5.       MARKETABLE SECURITIES
	NU maintains trusts to fund certain non-qualified executive benefits and WMECO maintains a spent nuclear fuel trust to fund WMECO's prior period spent nuclear fuel liability. These trusts hold marketable securities. These trusts are not subject to regulatory oversight by state or federal agencies. In addition, CYAPC and YAEC maintain legally restricted trusts, each of which holds marketable securities, for settling the decommissioning obligations of their nuclear power plants.
	In accordance with applicable accounting guidance, the Company elected to record mutual funds designated as available-for-sale at fair value and certain other equity investments as trading securities, with the changes in fair values recorded in Other Income, Net on the statements of income. As of June 30, 2014, the mutual funds and equity investments were classified as Level 1 in the fair value hierarchy and totaled $59.6 million and $24.9 million, respectively. As of December 31, 2013, the mutual funds were classified as Level 1, and totaled $57.2 million. Net gains on the mutual funds were $2.2 million and $0.1 million for the three months ended June 30, 2014 and 2013, respectively, and $2.4 million and $4.3 million for the six months ended June 30, 2014 and 2013, respectively. Net gains on the equity investments were $0.9 million and $1.4 million for the three and six months ended June 30, 2014, respectively. Dividend income is recorded in Other Income, Net on the statements of income when dividends are declared. All other marketable securities are accounted for as available-for-sale.
	Available-for-Sale Securities: The following is a summary of NU's and WMECO's available-for-sale securities. These securities are recorded at fair value and included in current and long-term Marketable Securities on the balance sheets.
	U.S. government issued debt securities are valued using market approaches that incorporate transactions for the same or similar bonds and adjustments for yields and maturity dates. Corporate debt securities are valued using a market approach, utilizing recent trades of the same or similar instrument and also incorporating yield curves, credit spreads and specific bond terms and conditions. Asset-backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset-backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates and tranche information. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.
Environmental Costs Policy	'
	Environmental Matters
	General: NU, CL&P, NSTAR Electric, PSNH and WMECO are subject to environmental laws and regulations intended to mitigate or remove the effect of past operations and improve or maintain the quality of the environment. These laws and regulations require the removal or the remedy of the effect on the environment of the disposal or release of certain specified hazardous substances at current and former operating sites. NU, CL&P, NSTAR Electric, PSNH and WMECO have an active environmental auditing and training program and believe that they are substantially in compliance with all enacted laws and regulations.
Earnings Per Share Policy Text Block	'
	Basic EPS is computed based upon the weighted average number of common shares outstanding during each period. Diluted EPS is computed on the basis of the weighted average number of common shares outstanding plus the potential dilutive effect of certain share-based compensation awards as if they were converted into common shares.
	RSUs and performance shares are included in basic weighted average common shares outstanding as of the date that all necessary vesting conditions have been satisfied. The dilutive effect of unvested RSUs and performance shares is calculated using the treasury stock method. Assumed proceeds of these units under the treasury stock method consist of the remaining compensation cost to be recognized and a theoretical tax benefit. The theoretical tax benefit is calculated as the tax impact of the intrinsic value of the units (the difference between the market value of the average units outstanding for the period, using the average market price during the period, and the grant date market value).
	The dilutive effect of stock options to purchase common shares is also calculated using the treasury stock method. Assumed proceeds for stock options consist of cash proceeds that would be received upon exercise, and a theoretical tax benefit. The theoretical tax benefit is calculated as the tax impact of the intrinsic value of the stock options (the difference between the market value of the average stock options outstanding for the period, using the average market price during the period, and the exercise price).
Segment Reporting Policy Policy Text Block	'
	SEGMENT INFORMATION
	Presentation: NU is organized between the Electric Distribution, Electric Transmission and Natural Gas Distribution reportable segments and Other based on a combination of factors, including the characteristics of each segments' products and services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates. These reportable segments represented substantially all of NU's total consolidated revenues for the three and six months ended June 30, 2014 and 2013. Revenues from the sale of electricity and natural gas primarily are derived from residential, commercial and industrial customers and are not dependent on any single customer. The Electric Distribution reportable segment includes the generation activities of PSNH and WMECO.
	The remainder of NU's operations is presented as Other in the tables below and primarily consists of 1) the equity in earnings of NU parent from its subsidiaries and intercompany interest income, both of which are eliminated in consolidation, and interest expense related to the debt of NU parent, 2) the revenues and expenses of NU's service company, most of which are eliminated in consolidation, 3) the operations of CYAPC and YAEC, and 4) the results of other non-regulated subsidiaries, which are not part of its core business.
	Cash flows used for investments in plant included in the segment information below are cash capital expenditures that do not include amounts incurred but not paid, cost of removal, AFUDC related to equity funds, and the capitalized portions of pension expense.

Provision_for_Uncollectible_Ac

Provision for Uncollectible Accounts (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Accounts Notes Loans And Financing Receivable Text Block	'
	(Millions of Dollars)	As of June 30, 2014		As of December 31, 2013
	NU	$	197.4	$	171.3
	CL&P		91.8		82
	NSTAR Electric		44.4		41.7
	PSNH		9.2		7.4
	WMECO		12.9		10

Other_Taxes_Tables

Other Taxes (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
State Of Connecticut Gross Earnings Taxes [Table Text Block]	'
		For the Three Months Ended				For the Six Months Ended
	(Millions of Dollars)	30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	NU	$	35.2	$	33	$	79.6	$	71.4
	CL&P		30.9		29.8		66.5		61.8

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	'
	G.	Supplemental Cash Flow Information
	Non-cash investing activities include plant additions included in Accounts Payable as follows:
	(Millions of Dollars)		As of June 30, 2014		As of June 30, 2013
	NU		$	125.5	$	109.5
	CL&P			54		28.3
	NSTAR Electric			21.6		33.4
	PSNH			14.8		15.5
	WMECO			9.9		17

REGULATORY_ACCOUNTING_Tables

REGULATORY ACCOUNTING (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Regulatory Assets Text Block	'
		As of June 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Benefit Costs	$	1,146.70		$	1,240.20
	Derivative Liabilities		431.4			638
	Income Taxes, Net		631.8			626.2
	Storm Restoration Costs		503.9			589.6
	Goodwill-related		515.7			525.9
	Regulatory Tracker Mechanisms		275.1			323.4
	Contractual Obligations - Yankee Companies		128.4			154.2
	Buy Out Agreements for Power Contracts		56.7			70.2
	Other Regulatory Assets		117			126.8
	Total Regulatory Assets		3,806.70			4,294.50
	Less: Current Portion		467.2			535.8
	Total Long-Term Regulatory Assets	$	3,339.50		$	3,758.70
			As of June 30, 2014									As of December 31, 2013
						NSTAR								NSTAR
	(Millions of Dollars)		CL&P			Electric		PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Benefit Costs		$	251.9		$	323.4	$	81.6	$	46.2	$	297.7	$	496.7	$	100.6	$	57.3
	Derivative Liabilities			424.6			6.3		-		-		630.4		7.7		-		-
	Income Taxes, Net			426.2			81.4		38		40.8		415.5		84		40.3		43.7
	Storm Restoration Costs			328			107.2		34.7		34		397.8		109.3		43.7		38.8
	Goodwill-related			-			442.8		-		-		-		451.5		-		-
	Regulatory Tracker Mechanisms			8.1			131.8		87.9		20.7		8		169.5		83.3		32.6
	Buy Out Agreements for Power Contracts			-			52		4.7		-		-		64.7		5.5		-
	Other Regulatory Assets			63.7			54.7		36		14.9		64.6		55.9		38.1		16.7
	Total Regulatory Assets			1,502.50			1,199.60		282.9		156.6		1,814.00		1,439.30		311.5		189.1
	Less: Current Portion			110			178.6		95.3		36.3		150.9		204.1		92.2		43
	Total Long-Term Regulatory Assets		$	1,392.50		$	1,021.00	$	187.6	$	120.3	$	1,663.10	$	1,235.20	$	219.3	$	146.1
Schedule Of Regulatory Liabilities Text Block	'
		As of June 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Cost of Removal	$	435.3		$	435.1
	Regulatory Tracker Mechanisms		305.2			151.2
	AFUDC - Transmission		67.4			68.1
	Other Regulatory Liabilities		56			52.9
	Total Regulatory Liabilities		863.9			707.3
	Less: Current Portion		359.9			204.3
	Total Long-Term Regulatory Liabilities	$	504		$	503
			As of June 30, 2014									As of December 31, 2013
						NSTAR								NSTAR
	(Millions of Dollars)		CL&P			Electric		PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Cost of Removal		$	22.8		$	255.7	$	48.7	$	-	$	29.1	$	250	$	49.7	$	-
	Regulatory Tracker Mechanisms			143.2			60.2		34.8		45.1		95.6		21.9		21.6		21.1
	AFUDC - Transmission			54.2			4		-		9.2		54.7		4.1		-		9.3
	Other Regulatory Liabilities			10			29.8		3.9		0.7		8.4		31.1		1		3.4
	Total Regulatory Liabilities			230.2			349.7		87.4		55		187.8		307.1		72.3		33.8
	Less: Current Portion			143.5			89.2		36.6		44.7		94		54		20.6		19.9
	Total Long-Term Regulatory Liabilities		$	86.7		$	260.5	$	50.8	$	10.3	$	93.8	$	253.1	$	51.7	$	13.9

PROPERTY_PLANT_AND_ACCUMULATED1

PROPERTY, PLANT AND ACCUMULATED DEPRECIATION (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Public Utility Property, Plant, and Equipment [Text Block]	'
				As of June 30, 2014			As of December 31, 2013
	(Millions of Dollars)			NU			NU
	Distribution - Electric			$	12,145.00		$	11,950.20
	Distribution - Natural Gas				2,467.40			2,425.90
	Transmission				6,508.00			6,412.50
	Generation				1,167.90			1,152.30
	Electric and Natural Gas Utility				22,288.30			21,940.90
	Other (1)				506.5			508.7
	Property, Plant and Equipment, Gross				22,794.80			22,449.60
	Less: Accumulated Depreciation
		Electric and Natural Gas Utility			-5,575.80			-5,387.00
		Other			-207.7			-196.2
	Total Accumulated Depreciation				-5,783.50			-5,583.20
	Property, Plant and Equipment, Net				17,011.30			16,866.40
	Construction Work in Progress				967.4			709.8
	Total Property, Plant and Equipment, Net			$	17,978.70		$	17,576.20
		As of June 30, 2014										As of December 31, 2013
					NSTAR									NSTAR
	(Millions of Dollars)	CL&P			Electric			PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Distribution	$	5,035.20		$	4,754.40		$	1,629.10	$	766.3	$	4,930.70	$	4,694.70	$	1,608.20	$	756.6
	Transmission		3,108.10			1,798.90			713.5		841.1		3,071.90		1,772.30		695.7		826.4
	Generation		-			-			1,134.00		33.9		-		-		1,131.20		21.1
	Property, Plant and Equipment, Gross		8,143.30			6,553.30			3,476.60		1,641.30		8,002.60		6,467.00		3,435.10		1,604.10
	Less: Accumulated Depreciation		-1,867.90			-1,700.60			-1,045.30		-283.7		-1,804.10		-1,631.30		-1,021.80		-271.5
	Property, Plant and Equipment, Net		6,275.40			4,852.70			2,431.30		1,357.60		6,198.50		4,835.70		2,413.30		1,332.60
	Construction Work in Progress		317.4			294.5			88.6		61.1		252.8		208.2		54.3		48.5
	Total Property, Plant and Equipment, Net	$	6,592.80		$	5,147.20		$	2,519.90	$	1,418.70	$	6,451.30	$	5,043.90	$	2,467.60	$	1,381.10

DERIVATIVE_INSTRUMENTS_Tables

DERIVATIVE INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Derivative Instruments In Statement Of Financial Position Fair Value Text Block	'
			As of June 30, 2014
			Commodity Supply and						Net Amount Recorded as
	(Millions of Dollars)		Price Risk Management			Netting (1)			Derivative Asset/(Liability)
	Current Derivative Assets:
	Level 2:
		NU (1)	$	0.4		$	-0.1		$	0.3
	Level 3:
		NU, CL&P (1)		16.4			-4.8			11.6
	Long-Term Derivative Assets:
	Level 3:
		NU, CL&P (1)	$	111.7		$	-17		$	94.7
	Current Derivative Liabilities:
	Level 2:
		NU (1)	$	-0.7		$	0.2		$	-0.5
	Level 3:
		NU		-87.8			-			-87.8
		CL&P		-85.6			-			-85.6
		NSTAR Electric		-2.2			-			-2.2
	Long-Term Derivative Liabilities:
	Level 3:
		NU	$	-449.4		$	-		$	-449.4
		CL&P		-445.3			-			-445.3
		NSTAR Electric		-4.1			-			-4.1
			As of December 31, 2013
			Commodity Supply and						Net Amount Recorded as
	(Millions of Dollars)		Price Risk Management			Netting (1)			Derivative Asset/(Liability)
	Current Derivative Assets:
	Level 2:
		NU (1)	$	1.9		$	-0.3		$	1.6
	Level 3:
		NU (1)		18.4			-9.8			8.6
		CL&P (1)		17.1			-9.8			7.3
		NSTAR Electric		1.2			-			1.2
	Long-Term Derivative Assets:
	Level 2:
		NU	$	0.2		$	-		$	0.2
	Level 3:
		NU (1)		116.2			-42.2			74
		CL&P (1)		113.6			-42.2			71.4
	Current Derivative Liabilities:
	Level 3:
		NU	$	-93.7		$	-		$	-93.7
		CL&P		-92.2			-			-92.2
		NSTAR Electric		-1.5			-			-1.5
	Long-Term Derivative Liabilities:
	Level 3:
		NU	$	-624.1		$	-		$	-624.1
		CL&P		-617.1			-			-617.1
		NSTAR Electric		-7			-			-7
Schedule Of Derivative Instruments Gain Loss In Statement Of Financial Performance Text Block	'
				Amounts Recognized on Derivatives
				For the Three Months Ended June 30,							For the Six Months Ended June 30,
	(Millions of Dollars)			2014			2013				2014			2013
	NU
	Balance Sheets:
		Regulatory Assets and Liabilities		$	111.6		$	22.2			$	166		$	50.1
	Statements of Income:
		Purchased Power, Fuel and Transmission			-			0.5				-			0.8
Rollforward Of Net Derivative Asset Liabilities Valued Using Unobservable Inputs [Table Text Block]	'
			For the Three Months Ended June 30,						For the Six Months Ended June 30,
			2014			2013			2014			2013
	(Millions of Dollars)		NU			NU			NU			NU
	Derivatives, Net:
	Fair Value as of Beginning of Period		$	-564.3		$	-833.1		$	-635.2		$	-878.6
	Net Realized/Unrealized Gains Included in:
		Net Income		-			1.3			-			7.1
		Regulatory Assets and Liabilities		111.8			22.7			161.3			48.9
	Settlements			21.6			21			43			34.5
	Fair Value as of End of Period		$	-430.9		$	-788.1		$	-430.9		$	-788.1
			For the Three Months Ended June 30,
			2014							2013
	(Millions of Dollars)		CL&P			NSTAR Electric				CL&P			NSTAR Electric
	Derivatives, Net:
	Fair Value as of Beginning of Period		$	-557		$	-7.3			$	-819.6		$	-13.6
	Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities			112.2			-0.4				21.9			-0.5
	Settlements			20.2			1.4				21.9			1
	Fair Value as of End of Period		$	-424.6		$	-6.3			$	-775.8		$	-13.1
			For the Six Months Ended June 30,
			2014							2013
	(Millions of Dollars)		CL&P			NSTAR Electric				CL&P			NSTAR Electric
	Derivatives, Net:
	Fair Value as of Beginning of Period		$	-630.6		$	-7.3			$	-866.2		$	-14.9
	Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities			164.5			-0.5				46.3			0.2
	Settlements			41.5			1.5				44.1			1.6
	Fair Value as of End of Period		$	-424.6		$	-6.3			$	-775.8		$	-13.1
Fairvalueinputsliabilitiesquantitativeinformationtabletextblock	'
		As of June 30, 2014									As of December 31, 2013
			Range						Period Covered			Range					Period Covered
	Energy Prices:
	NU	$	63	-	66	per MWh			2018 - 2020		$	49	-	77	per MWh		2018 - 2029
	CL&P	$	63	-	66	per MWh			2018 - 2020		$	56	-	58	per MWh		2018 - 2029
	Capacity Prices:
	NU	$	3.13	-	13		per kW-Month		2016 - 2026		$	5.07	-	11.82		per kW-Month	2017 - 2029
	CL&P	$	7	-	13		per kW-Month		2018 - 2026		$	5.07	-	10.42		per kW-Month	2017 - 2026
	NSTAR Electric	$	3.13	-	11.13		per kW-Month		2016 - 2019		$	5.07	-	7.38		per kW-Month	2017 - 2019
	Forward Reserve:
	NU, CL&P	$	3.3	-	9.5		per kW-Month		2014 - 2024		$	3.3	-	3.3		per kW-Month	2014 - 2024
	REC Prices:
	NU	$	38	-	70	per REC			2014 - 2018		$	36	-	87	per REC		2014 - 2029
	NSTAR Electric	$	38	-	70	per REC			2014 - 2018		$	36	-	70	per REC		2014 - 2018

MARKETABLE_SECURITIES_Tables

MARKETABLE SECURITIES (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Available For Sale Securities Reconciliation [Table TextBlock]	'
			As of June 30, 2014
						Pre-Tax			Pre-Tax
			Amortized			Unrealized			Unrealized
	(Millions of Dollars)		Cost			Gains			Losses			Fair Value
	NU
		Debt Securities (1)	$	308.3		$	7.3		$	-0.3		$	315.3
		Equity Securities (1)		163.5			66.7			-			230.2
	WMECO
		Debt Securities (2)		58			-			-			58
			As of December 31, 2013
						Pre-Tax			Pre-Tax
			Amortized			Unrealized			Unrealized
	(Millions of Dollars)		Cost			Gains			Losses			Fair Value
	NU
		Debt Securities (1)	$	299.2		$	2.5		$	-2.1		$	299.6
		Equity Securities (1)		163.6			60.5			-			224.1
	WMECO
		Debt Securities (2)		57.9			-			-			57.9
Investments Classified by Contractual Maturity Date [Table Text Block]	'
			NU						WMECO
			Amortized						Amortized
	(Millions of Dollars)		Cost			Fair Value			Cost			Fair Value
	Less than one year (1)		$	75.9		$	75.8		$	19.2		$	19.2
	One to five years			73.9			74.6			31.9			32
	Six to ten years			56.1			57.7			2.7			2.7
	Greater than ten years			102.4			107.2			4.2			4.1
	Total Debt Securities		$	308.3		$	315.3		$	58		$	58
Fair Value Heirarchy [Table Text Block]	'
					NU						WMECO
					As of						As of
	(Millions of Dollars)				30-Jun-14			31-Dec-13			30-Jun-14			31-Dec-13
	Level 1:
		Mutual Funds and Equities			$	314.7		$	281.3		$	-		$	-
		Money Market Funds				42.3			32.9			2			10.9
	Total Level 1				$	357		$	314.2		$	2		$	10.9
	Level 2:
		U.S. Government Issued Debt Securities (Agency and Treasury)			$	40.6		$	61.4		$	-		$	6.8
		Corporate Debt Securities				61.8			53.6			15.8			15.1
		Asset-Backed Debt Securities				36.5			30.4			15.2			9
		Municipal Bonds				109.5			105.5			11.7			11.2
		Other Fixed Income Securities				24.6			15.8			13.3			4.9
	Total Level 2				$	273		$	266.7		$	56		$	47
	Total Marketable Securities				$	630		$	580.9		$	58		$	57.9

Recovered_Sheet1

Pension Benefits and Postretirement Benefits Other Than Pensions (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Net Benefit Costs [Table Text Block]	'
		Pension and SERP				Pension and SERP
		For the Three Months Ended				For the Six Months Ended
		30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	19.1	$	24.6	$	41.5	$	51.1
	Interest Cost		56.3		51.9		113		103.5
	Expected Return on Plan Assets		-77.7		-68.6		-155.4		-139
	Actuarial Loss		31.7		52.6		64.7		105.5
	Prior Service Cost		1.1		1		2.1		2.1
	Total Net Periodic Benefit Expense	$	30.5	$	61.5	$	65.9	$	123.2
	Capitalized Pension Expense	$	8.7	$	19.9	$	18.4	$	36.6
		PBOP				PBOP
		For the Three Months Ended				For the Six Months Ended
		30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	3.2	$	3.7	$	6.3	$	8.5
	Interest Cost		12.1		10.9		24.7		23.6
	Expected Return on Plan Assets		-15.8		-13.9		-31.6		-27.7
	Actuarial Loss		3		4.7		6		13
	Prior Service Credit		-0.7		-0.5		-1.4		-1.1
	Total Net Periodic Benefit Expense	$	1.8	$	4.9	$	4	$	16.3
	Capitalized PBOP Expense	$	0.4	$	1.5	$	0.8	$	5
		Pension and SERP
		For the Three Months Ended June 30, 2014								For the Three Months Ended June 30, 2013
				NSTAR								NSTAR
	(Millions of Dollars)	CL&P		Electric		PSNH		WMECO		CL&P		Electric(1)		PSNH		WMECO
	Service Cost	$	5	$	3	$	2.3	$	0.8	$	6.3	$	7.3	$	3.2	$	1.2
	Interest Cost		12.4		10.3		5.8		2.5		12.1		14.7		5.9		2.5
	Expected Return on Plan Assets		-18.7		-15.7		-9.3		-4.4		-18.4		-20.2		-9.2		-4.4
	Actuarial Loss		8.2		5.9		2.8		1.7		13.9		14.6		5.4		2.9
	Prior Service Cost/(Credit)		0.5		-		0.1		0.1		0.5		-0.1		0.1		0.1
	Total Net Periodic Benefit Expense	$	7.4	$	3.5	$	1.7	$	0.7	$	14.4	$	16.3	$	5.4	$	2.3
	Intercompany Allocations	$	7.5	$	1.4	$	2.1	$	1.4	$	11.3	$	-2.2	$	2.6	$	2
	Capitalized Pension Expense	$	4.4	$	1	$	0.8	$	0.6	$	7	$	6.5	$	1.7	$	1.3
		Pension and SERP
		For the Six Months Ended June 30, 2014								For the Six Months Ended June 30, 2013
				NSTAR								NSTAR
	(Millions of Dollars)	CL&P		Electric		PSNH		WMECO		CL&P		Electric(1)		PSNH		WMECO
	Service Cost	$	10.2	$	7.6	$	5.1	$	1.9	$	12.4	$	16.5	$	6.5	$	2.4
	Interest Cost		25.7		20.6		12.3		5.2		24.2		29		11.9		5
	Expected Return on Plan Assets		-38		-31.5		-19.5		-9		-36.9		-42.2		-16.8		-8.7
	Actuarial Loss		17.3		11.7		6		3.5		28		29.1		10.8		5.9
	Prior Service Cost/(Credit)		0.9		-		0.3		0.2		0.9		-0.1		0.3		0.2
	Total Net Periodic Benefit Expense	$	16.1	$	8.4	$	4.2	$	1.8	$	28.6	$	32.3	$	12.7	$	4.8
	Intercompany Allocations	$	14.3	$	3.8	$	4.2	$	2.7	$	22.1	$	-4.1	$	5.2	$	4
	Capitalized Pension Expense	$	9.3	$	2.9	$	1.7	$	1.4	$	14	$	11.8	$	3.9	$	2.6
		PBOP
		For the Three Months Ended June 30, 2014								For the Three Months Ended June 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	0.5	$	0.8	$	0.3	$	0.1	$	0.9	$	0.6	$	0.2
	Interest Cost		1.9		4.8		1		0.4		2		1		0.4
	Expected Return on Plan Assets		-2.5		-6.5		-1.3		-0.6		-2.5		-1.3		-0.6
	Actuarial Loss/(Gain)		1		-0.2		0.6		0.1		1.9		0.9		0.3
	Prior Service Credit		-		-0.5		-		-		-		-		-
	Total Net Periodic Benefit Expense/(Income)	$	0.9	$	-1.6	$	0.6	$	0	$	2.3	$	1.2	$	0.3
	Intercompany Allocations	$	1.1	$	-	$	0.3	$	0.2	$	1.9	$	0.4	$	0.3
	Capitalized PBOP Expense/(Income)	$	0.5	$	-0.5	$	0.2	$	-	$	1.2	$	0.4	$	0.2
		PBOP
		For the Six Months Ended June 30, 2014								For the Six Months Ended June 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	1.1	$	1.6	$	0.7	$	0.2	$	1.7	$	1.1	$	0.4
	Interest Cost		4		9.7		2.1		0.8		3.9		2		0.8
	Expected Return on Plan Assets		-5.2		-13		-2.7		-1.1		-5		-2.6		-1.2
Actuarial Loss/(Gain)		2.1		-0.3		1.1		0.2		3.7		1.8		0.6
Prior Service Credit		-		-0.9		-		-		-		-		-
Total Net Periodic Benefit Expense/(Income)	$	2	$	-2.9	$	1.2	$	0.1	$	4.3	$	2.3	$	0.6
Intercompany Allocations	$	2.2	$	0.1	$	0.6	$	0.4	$	3.6	$	0.8	$	0.6
Capitalized PBOP Expense/(Income)	$	1	$	-1	$	0.4	$	0.1	$	2.4	$	0.7	$	0.4

Environmental_Matters_Tables

Environmental Matters (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Environmental Loss Contingencies By Site Text Block	'
		As of June 30, 2014				As of December 31, 2013
				Reserve				Reserve
		Number of Sites		(in millions)		Number of Sites		(in millions)
	NU		66	$	34.5		68	$	35.4
	CL&P		17		4.2		18		3.4
	NSTAR Electric		14		1.2		12		1.2
	PSNH		13		5.3		15		5.4
	WMECO		5		0.6		5		0.4

LongTerm_Contractual_Arrangeme

Long-Term Contractual Arrangements (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Long-term Purchase Commitment [Table Text Block]	'
		July - December
	(Millions of Dollars)	2014		2015		2016		2017		2018		Thereafter		Total
	Renewable Energy
	NSTAR Electric	$	43.6	$	86.3	$	93.7	$	89.8	$	53.3	$	302.8	$	669.5
	WMECO		-		-		2.4		2.4		2.4		28.9		36.1

Guarantees_and_Indemnification

Guarantees and Indemnifications (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Guarantee Obligations Text Block	'
			Maximum Exposure
	Subsidiary	Description	(in millions)		Expiration Dates
	Various	Surety Bonds	$	67	2014 - 2016 (1)
	Various	New England Hydro Companies' Long-Term Debt	$	2.5	Unspecified
	NUSCO and RRR	Lease Payments for Vehicles and Real Estate	$	16	2019 and 2024

FAIR_VALUE_OF_FINANCIAL_INSTRU1

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Fair Value By Balance Sheet Grouping Text Block	'
		As of June 30, 2014				As of December 31, 2013
		NU				NU
		Carrying		Fair		Carrying		Fair
	(Millions of Dollars)	Amount		Value		Amount		Value
	Preferred Stock Not Subject to Mandatory Redemption	$	155.6	$	150.1	$	155.6	$	152.7
	Long-Term Debt		8,542.70		9,008.40		8,310.20		8,443.10
		As of June 30, 2014
		CL&P				NSTAR Electric				PSNH				WMECO
		Carrying		Fair		Carrying		Fair		Carrying		Fair		Carrying		Fair
	(Millions of Dollars)	Amount		Value		Amount		Value		Amount		Value		Amount		Value
	Preferred Stock Not Subject to Mandatory Redemption	$	116.2	$	110.3	$	43	$	39.8	$	-	$	-	$	-	$	-
	Long-Term Debt		2,991.60		3,344.50		1,797.40		1,949.80		1,049.20		1,105.80		628.9		665.3
		As of December 31, 2013
		CL&P				NSTAR Electric				PSNH				WMECO
		Carrying		Fair		Carrying		Fair		Carrying		Fair		Carrying		Fair
	(Millions of Dollars)	Amount		Value		Amount		Value		Amount		Value		Amount		Value
	Preferred Stock Not Subject to Mandatory Redemption	$	116.2	$	110.5	$	43	$	42.2	$	-	$	-	$	-	$	-
	Long-Term Debt		2,741.20		2,952.80		1,801.10		1,888.00		1,049.00		1,073.90		629.4		640.1

ACCUMULATED_OTHER_COMPREHENSIV1

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Accumulated Other Comprehensive Income Loss Table Text Block	'
			For the Six Months Ended June 30, 2014												For the Six Months Ended June 30, 2013
						Unrealized			Pension,								Unrealized		Pension,
			Qualified			Gains/(Losses)			SERP and						Qualified		Gains/(Losses)		SERP and
			Cash Flow			on Available-			PBOP						Cash Flow		on Available-		PBOP
			Hedging			for-Sale			Benefit						Hedging		for-Sale		Benefit
	(Millions of Dollars)		Instruments			Securities			Plans			Total			Instruments		Securities		Plans		Total
	AOCI as of Beginning of Period		$	-14.4		$	0.4		$	-32		$	-46		$	-16.4	$	1.3	$	-57.8	$	-72.9
	OCI Before Reclassifications			-			0.5			1.2			1.7			-		-0.7		-		-0.7
	Amounts Reclassified from AOCI			1			-			1.8			2.8			1		-		3.1		4.1
	Net OCI			1			0.5			3			4.5			1		-0.7		3.1		3.4
	AOCI as of End of Period		$	-13.4		$	0.9		$	-29		$	-41.5		$	-15.4	$	0.6	$	-54.7	$	-69.5
		For the Three Months Ended						For the Six Months Ended
		June 30,						June 30,
		Amounts Reclassified						Amounts Reclassified						Statements of Income
		from AOCI						from AOCI						Line Item Impacted
	(Millions of Dollars)	2014			2013			2014			2013
	Qualified Cash Flow Hedging Instruments	$	-0.8		$	-0.8		$	-1.7		$	-1.7		Interest Expense
	Tax Benefit		0.3			0.3			0.7			0.7		Income Tax Expense
	Qualified Cash Flow Hedging Instruments, Net of Tax	$	-0.5		$	-0.5		$	-1		$	-1
	Pension, SERP and PBOP Benefit Plan Costs:
	Amortization of Actuarial Losses	$	-1.2		$	-2.2		$	-2.9		$	-4.7		Operations and Maintenance (1)
	Amortization of Prior Service Cost		-			-			-0.1			-0.1		Operations and Maintenance (1)
	Total Pension, SERP and PBOP Benefit Plan Costs		-1.2			-2.2			-3			-4.8
	Tax Benefit		0.5			0.7			1.2			1.7		Income Tax Expense
	Pension, SERP and PBOP Benefit Plan Costs, Net of Tax	$	-0.7		$	-1.5		$	-1.8		$	-3.1
	Total Amounts Reclassified from AOCI, Net of Tax	$	-1.2		$	-2		$	-2.8		$	-4.1

COMMON_SHARES_Tables

COMMON SHARES (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Stock by Class [Text Block]	'
	11.       COMMON SHARES
	The following table sets forth the NU common shares and the shares of common stock of CL&P, NSTAR Electric, PSNH and WMECO that were authorized and issued and the respective per share par values:
		Shares
				Authorized as of
		Per Share		June 30, 2014 and	Issued as of
		Par Value		31-Dec-13	30-Jun-14	31-Dec-13
	NU	$	5	380,000,000	333,327,485	333,113,492
	CL&P	$	10	24,500,000	6,035,205	6,035,205
	NSTAR Electric	$	1	100,000,000	100	100
	PSNH	$	1	100,000,000	301	301
	WMECO	$	25	1,072,471	434,653	434,653
	As of June 30, 2014 and December 31, 2013, there were 17,108,131 and 17,796,672 NU common shares held as treasury shares, respectively. As of June 30, 2014 and December 31, 2013, NU common shares outstanding were 316,219,354 and 315,273,559, respectively.

COMMON_SHARESHOLDERS_EQUITY_AN1

COMMON SHARESHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (NU) (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Minority Interest Disclosure Text Block	'
	12	COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS
	A summary of the changes in Common Shareholders' Equity and Noncontrolling Interests of NU is as follows:
			For the Three Months Ended
			30-Jun-14				30-Jun-13
					Noncontrolling				Noncontrolling
					Interest -				Interest -
			Common		Preferred		Common		Preferred
			Shareholders'		Stock of		Shareholders'		Stock of
	(Millions of Dollars)		Equity		Subsidiaries		Equity		Subsidiaries
	Balance as of Beginning of Period		$	9,723.90	$	155.6	$	9,345.20	$	155.6
	Net Income			129.2		-		173.1		-
	Dividends on Common Shares			-124.1		-		-115.6		-
	Dividends on Preferred Stock			-1.9		-1.9		-2		-2
	Issuance of Common Shares			0.2		-		0.3		-
	Other Transactions, Net			23.7		-		4.2		-
	Net Income Attributable to Noncontrolling Interests			-		1.9		-		2
	Other Comprehensive Income			2.8		-		1.4		-
	Balance as of End of Period		$	9,753.80	$	155.6	$	9,406.60	$	155.6
			For the Six Months Ended
			30-Jun-14				30-Jun-13
					Noncontrolling				Noncontrolling
					Interest -				Interest -
			Common		Preferred		Common		Preferred
			Shareholders'		Stock of		Shareholders'		Stock of
	(Millions of Dollars)		Equity		Subsidiaries		Equity		Subsidiaries
	Balance as of Beginning of Period		$	9,611.50	$	155.6	$	9,237.10	$	155.6
	Net Income			367.1		-		403		-
	Dividends on Common Shares			-247.9		-		-232.1		-
	Dividends on Preferred Stock			-3.8		-3.8		-3.9		-3.9
	Issuance of Common Shares			5.4		-		8.8		-
	Other Transactions, Net			17		-		-9.7		-
	Net Income Attributable to Noncontrolling Interests			-		3.8		-		3.9
	Other Comprehensive Income			4.5		-		3.4		-
	Balance as of End of Period		$	9,753.80	$	155.6	$	9,406.60	$	155.6

EARNINGS_PER_SHARE_Tables

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Earnings Per Share Basic And Diluted [Table Text Block]	'
			For the Three Months Ended				For the Six Months Ended
	(Millions of Dollars, except share information)		30-Jun-14		30-Jun-13		30-Jun-14		30-Jun-13
	Net Income Attributable to Controlling Interest		$	127.4	$	171	$	363.3	$	399.1
	Weighted Average Common Shares Outstanding:
		Basic		315,950,510		315,154,130		315,742,511		315,141,956
		Dilutive Effect		1,162,291		808,489		1,259,950		840,622
		Diluted		317,112,801		315,962,619		317,002,461		315,982,578
	Basic EPS		$	0.4	$	0.54	$	1.15	$	1.27
	Diluted EPS		$	0.4	$	0.54	$	1.15	$	1.26

SEGMENT_INFORMATION_Tables

SEGMENT INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2014
Segment Reporting Information [Line Items]	'
Schedule Of Segment Reporting Information By Segment Text Block	'
		For the Three Months Ended June 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,261.80	$	195.5	$	206.9	$	184.7	$	-171.3	$	1,677.60
	Depreciation and Amortization		-89.3		-16.9		-37		-7.7		2.3		-148.6
	Other Operating Expenses		-991.5		-166.5		-71		-174.9		168.9		-1,235.00
	Operating Income		181		12.1		98.9		2.1		-0.1		294
	Interest Expense		-47.2		-8.7		-28.8		-9.1		1.3		-92.5
	Other Income, Net		2.9		-		2.7		137.7		-137.8		5.5
	Net Income Attributable to Controlling Interest	$	83.4	$	2	$	43.9	$	133.3	$	-135.2	$	127.4
		For the Six Months Ended June 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	2,847.80	$	628.3	$	458.9	$	356.9	$	-323.7	$	3,968.20
	Depreciation and Amortization		-238.2		-34.6		-74		-14.7		4.1		-357.4
	Other Operating Expenses		-2,202.40		-487.9		-137.3		-340.3		318.8		-2,849.10
	Operating Income		407.2		105.8		247.6		1.9		-0.8		761.7
	Interest Expense		-94.6		-17.1		-54.3		-18.7		2.2		-182.5
	Other Income, Net		4.3		0.1		4.2		432.4		-433.8		7.2
	Net Income Attributable to Controlling Interest	$	195.6	$	54.1	$	118.8	$	424.9	$	-430.1	$	363.3
	Cash Flows Used for Investments in Plant	$	335.6	$	68.6	$	289.3	$	30.5	$	-	$	724
		For the Three Months Ended June 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,221.60	$	154.1	$	247.9	$	220.7	$	-208.4	$	1,635.90
	Depreciation and Amortization		-152.2		-16.7		-34.5		-21.7		2.9		-222.2
	Other Operating Expenses		-883.3		-127		-63.6		-194.9		205.7		-1,063.10
	Operating Income		186.1		10.4		149.8		4.1		0.2		350.6
	Interest Expense		-43.4		-8.9		-25.2		-10.7		1.3		-86.9
	Other Income, Net		2.2		0.1		2.8		232.2		-232.3		5
	Net Income Attributable to Controlling Interest	$	91.2	$	1.2	$	76.8	$	232.8	$	-231	$	171
		For the Six Months Ended June 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	2,595.80	$	515.9	$	487.4	$	437.8	$	-406	$	3,630.90
	Depreciation and Amortization		-329.1		-34.1		-66.3		-40.8		4.6		-465.7
	Other Operating Expenses		-1,888.30		-394.3		-125.8		-392.2		404.9		-2,395.70
	Operating Income		378.4		87.5		295.3		4.8		3.5		769.5
	Interest Expense		-85.6		-16.2		-47.1		-17.1		2.9		-163.1
	Other Income, Net		7.1		0.3		5.5		554		-554.2		12.7
	Net Income Attributable to Controlling Interest	$	190.6	$	44.5	$	156.7	$	555.5	$	-548.2	$	399.1
	Cash Flows Used for Investments in Plant	$	315.3	$	70.9	$	297.4	$	16.7	$	-	$	700.3
	The following table summarizes NU's segmented total assets:
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	As of June 30, 2014	$	16,942.50	$	2,753.80	$	6,934.10	$	11,566.60	$	-10,406.60	$	27,790.40
	As of December 31, 2013		17,260.00		2,759.70		6,745.80		11,842.40		-10,812.40		27,795.50

Basis_of_Presentation_Details

Basis of Presentation (Details)	6 Months Ended
	Jun. 30, 2014
Description of Consolidation of Yankee Companies	'NU consolidates CYAPC and YAEC as CL&P’s, NSTAR Electric’s, PSNH’s and WMECO’s combined ownership interest in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and WMECO and the CYAPC and YAEC companies have been eliminated in consolidation of the NU financial statements. For CL&P, NSTAR Electric, PSNH and WMECO, the investments in CYAPC and YAEC continue to be accounted for under the equity method.

Provision_for_Uncollectible_Ac1

Provision for Uncollectible Accounts (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	$197.40	$171.30
The Connecticut Light And Power Company [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	91.8	82
NSTAR Electric Company [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	44.4	41.7
Public Service Company Of New Hampshire [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	9.2	7.4
Western Massachusetts Electric Company [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	$12.90	$10

Other_Taxes_Details

Other Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Excise And Sales Taxes	$35.20	$33	$79.60	$71.40
The Connecticut Light And Power Company [Member]	'	'	'	'
Excise And Sales Taxes	$30.90	$29.80	$66.50	$61.80

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Details) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Capital Expenditures Incurred But Not Yet Paid	$125.50	$109.50
Description of DOE Damages Claims Proceeds	'In the first half of 2014, as a result of awards issued to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 8C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," NU recognized total proceeds of $125.7 million, which were net of $80.6 million in proceeds CY and YAEC returned to non-affiliated member companies.	'
The Connecticut Light And Power Company [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	54	28.3
NSTAR Electric Company [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	21.6	33.4
Public Service Company Of New Hampshire [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	14.8	15.5
Western Massachusetts Electric Company [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	$9.90	$17

Severance_Benefits_Details

Severance Benefits (Details) (USD $)	3 Months Ended	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Notes To Consolidated Financial Statements [Abstract]	'	'	'
Description Of Postemployment Benefits	'	'Severance Benefits NU recorded severance benefit expenses of $1.4 million and $5.7 million associated with the partial outsourcing of information technology functions and ongoing post-merger integration for the three and six months ended June 30, 2014, respectively. As of June 30, 2014 and December 31, 2013, the severance accrual totaled $9.3 million and $14.7 million, respectively, and was included in Other Current Liabilities on the balance sheets.	'
Postemployment Benefits Period Expense	$1.40	$5.70	'
Postemployment Benefits Liability Current And Noncurrent	$9.30	$9.30	$14.70

REGULATORY_ACCOUNTING_Details

REGULATORY ACCOUNTING (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	$3,806,700,000	$4,294,500,000
Regulatory Assets Current	467,156,000	535,791,000
Regulatory Assets Long Term	3,339,457,000	3,758,694,000
Regulatory Assets And Liabilities Other Disclosures Abstract	'	'
Description of Regulatory Costs Not yet Approved	'Regulatory Costs in Other Long-Term Assets: The Regulated companies had $64.5 million ($3.4 million for CL&P, $33.9 million for NSTAR Electric, and $12 million for WMECO) and $65.1 million ($7.3 million for CL&P, $33.4 million for NSTAR Electric, and $10.1 million for WMECO) of additional regulatory costs as of June 30, 2014 and December 31, 2013, respectively, that were included in Other Long-Term Assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates.	'
Description Of Regulatory Costs Recently Approved	'Storm Restoration Costs: On March 12, 2014, the PURA approved recovery of $365 million of deferred storm restoration costs associated with five major storms that occurred in 2011 and 2012. CL&P will recover the $365 million with carrying charges in its distribution rates over a six-year period beginning December 1, 2014. On June 17, 2014, the PURA ordered CL&P to use the DOE Phase II Damages proceeds of $65.4 million to offset the $365 million in 2011 and 2012 deferred storm restoration costs, which are reflected in the deferred storm restoration costs regulatory asset. For further information on the DOE Phase II Damages proceeds received from the Yankee Companies, see Note 8C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," to the financial statements.	'
Description of Regulatory Assets and Liabilities	'As a result of two FERC orders issued on June 19, 2014 in the pending base ROE complaint proceedings described in Note 8E, "Commitments and Contingencies – FERC Base ROE Complaints," in the second quarter of 2014, the Company recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact of these rulings. The aggregate pre-tax charge totaled $54.7 million at NU, which represented reserves of $31.4 million at CL&P, $10.3 million at NSTAR Electric, $3.8 million at PSNH and $9.2 million at WMECO. As of June 30, 2014, the cumulative reserves totaled $79.3 million at NU, $44.7 million at CL&P, $16.2 million at NSTAR Electric, $6.2 million at PSNH and $12.2 million at WMECO. As of December 31, 2013, as a result of the FERC ALJ initial decision in the third quarter of 2013, the Company had an aggregate pre-tax reserve of $24.6 million at NU, which represented reserves of $13.3 million at CL&P, $5.9 million at NSTAR Electric, $2.4 million at PSNH and $3 million at WMECO. These reserves were recorded in each electric subsidiary's respective transmission regulatory tracker mechanism and as a reduction of operating revenues. As a result of awards issued to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 8C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," the Yankee Companies returned the DOE Phase II Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, for the benefit of their respective customers, effective June 1, 2014. CL&P’s refund obligation to customers of $65.4 million was recorded as an offset to the deferred storm restoration costs regulatory asset, as directed by PURA. NSTAR Electric’s, PSNH’s and WMECO’s refund obligation to customers of $29.1 million, $13.1 million and $18.1 million, respectively, was recorded as a regulatory liability in each electric subsidiary’s respective regulatory tracker mechanisms.	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	863,900,000	707,300,000
Regulatory Liability Current	359,921,000	204,278,000
Regulatory Liabilities Long-Term	503,955,000	502,984,000
Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	435,300,000	435,100,000
Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	305,200,000	151,200,000
AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	67,400,000	68,100,000
Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	56,000,000	52,900,000
The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	1,502,500,000	1,814,000,000
Regulatory Assets Current	109,951,000	150,943,000
Regulatory Assets Long Term	1,392,529,000	1,663,147,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	230,200,000	187,800,000
Regulatory Liability Current	143,457,000	93,961,000
Regulatory Liabilities Long-Term	86,677,000	93,757,000
The Connecticut Light And Power Company [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	22,800,000	29,100,000
The Connecticut Light And Power Company [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	143,200,000	95,600,000
The Connecticut Light And Power Company [Member] | AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	54,200,000	54,700,000
The Connecticut Light And Power Company [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	10,000,000	8,400,000
NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	1,199,600,000	1,439,300,000
Regulatory Assets Current	178,640,000	204,144,000
Regulatory Assets Long Term	1,020,990,000	1,235,156,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	349,700,000	307,100,000
Regulatory Liability Current	89,161,000	53,958,000
Regulatory Liabilities Long-Term	260,480,000	253,108,000
NSTAR Electric Company [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	255,700,000	250,000,000
NSTAR Electric Company [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	60,200,000	21,900,000
NSTAR Electric Company [Member] | AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	4,000,000	4,100,000
NSTAR Electric Company [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	29,800,000	31,100,000
Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	282,900,000	311,500,000
Regulatory Assets Current	95,270,000	92,194,000
Regulatory Assets Long Term	187,592,000	219,346,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	87,400,000	72,300,000
Regulatory Liability Current	36,627,000	20,643,000
Regulatory Liabilities Long-Term	50,843,000	51,723,000
Public Service Company Of New Hampshire [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	48,700,000	49,700,000
Public Service Company Of New Hampshire [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	34,800,000	21,600,000
Public Service Company Of New Hampshire [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	3,900,000	1,000,000
Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	156,600,000	189,100,000
Regulatory Assets Current	36,251,000	43,024,000
Regulatory Assets Long Term	120,303,000	146,088,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	55,000,000	33,800,000
Regulatory Liability Current	44,745,000	19,858,000
Regulatory Liabilities Long-Term	10,317,000	13,873,000
Western Massachusetts Electric Company [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	0	0
Western Massachusetts Electric Company [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	45,100,000	21,100,000
Western Massachusetts Electric Company [Member] | AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	9,200,000	9,300,000
Western Massachusetts Electric Company [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	700,000	3,400,000
Benefit Costs [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	1,146,700,000	1,240,200,000
Benefit Costs [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	251,900,000	297,700,000
Benefit Costs [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	323,400,000	496,700,000
Benefit Costs [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	81,600,000	100,600,000
Benefit Costs [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	46,200,000	57,300,000
Regulatory Assets Offsetting Derivative Liabilities [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	431,400,000	638,000,000
Regulatory Assets Offsetting Derivative Liabilities [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	424,600,000	630,400,000
Regulatory Assets Offsetting Derivative Liabilities [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	6,300,000	7,700,000
Regulatory Assets Offsetting Derivative Liabilities [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	0	0
Regulatory Assets Offsetting Derivative Liabilities [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	0	0
Deferred Income Tax Charges Member	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	631,800,000	626,200,000
Deferred Income Tax Charges Member | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	426,200,000	415,500,000
Deferred Income Tax Charges Member | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	81,400,000	84,000,000
Deferred Income Tax Charges Member | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	38,000,000	40,300,000
Deferred Income Tax Charges Member | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	40,800,000	43,700,000
Storm Restoration Costs [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	503,900,000	589,600,000
Storm Restoration Costs [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	328,000,000	397,800,000
Storm Restoration Costs [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	107,200,000	109,300,000
Storm Restoration Costs [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	34,700,000	43,700,000
Storm Restoration Costs [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	34,000,000	38,800,000
Goodwill Regulatory Asset [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	515,700,000	525,900,000
Goodwill Regulatory Asset [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	442,800,000	451,500,000
Regulatory Tracker Deferrals Regulatory Assets [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	275,100,000	323,400,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	8,100,000	8,000,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	131,800,000	169,500,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	87,900,000	83,300,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	20,700,000	32,600,000
Unrecovered Contractual Obligations [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	128,400,000	154,200,000
Power Contracts Buy Out Agreements [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	56,700,000	70,200,000
Power Contracts Buy Out Agreements [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	52,000,000	64,700,000
Power Contracts Buy Out Agreements [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	4,700,000	5,500,000
Other Regulatory Assets [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	117,000,000	126,800,000
Other Regulatory Assets [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	63,700,000	64,600,000
Other Regulatory Assets [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	54,700,000	55,900,000
Other Regulatory Assets [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	36,000,000	38,100,000
Other Regulatory Assets [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	$14,900,000	$16,700,000

PROPERTY_PLANT_AND_ACCUMULATED2

PROPERTY, PLANT AND ACCUMULATED DEPRECIATION (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	$12,145,000,000	$11,950,200,000
Public Utilities Property Plant And Equipment Distribution Natural Gas	2,467,400,000	2,425,900,000
Public Utilities Property Plant And Equipment Transmission	6,508,000,000	6,412,500,000
Public Utilities Property Plant And Equipment Generation Or Processing	1,167,900,000	1,152,300,000
Public Utilities Property Plant And Equipment Electric And Natural Gas Utility Total	22,288,300,000	21,940,900,000
Public Utilities Property Plant And Equipment Other Property Plant And Equipment	506,500,000	508,700,000
Public Utilities Property Plant And Equipment Plant In Service	22,794,800,000	22,449,600,000
Electric And Natural Gas Utility Accumulated Depreciation	-5,575,800,000	-5,387,000,000
Other Accumulated Depreciation	-207,700,000	-196,200,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-5,783,500,000	-5,583,200,000
Property Plant And Equipment Net Excluding Construction Work In Progress	17,011,300,000	16,866,400,000
Public Utilities Property Plant And Equipment Construction Work In Progress	967,400,000	709,800,000
Property, Plant and Equipment, Net	17,978,692,000	17,576,186,000
The Connecticut Light And Power Company [Member]	'	'
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	5,035,200,000	4,930,700,000
Public Utilities Property Plant And Equipment Transmission	3,108,100,000	3,071,900,000
Public Utilities Property Plant And Equipment Generation Or Processing	0	0
Public Utilities Property Plant And Equipment Plant In Service	8,143,300,000	8,002,600,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-1,867,900,000	-1,804,100,000
Property Plant And Equipment Net Excluding Construction Work In Progress	6,275,400,000	6,198,500,000
Public Utilities Property Plant And Equipment Construction Work In Progress	317,400,000	252,800,000
Property, Plant and Equipment, Net	6,592,833,000	6,451,259,000
NSTAR Electric Company [Member]	'	'
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	4,754,400,000	4,694,700,000
Public Utilities Property Plant And Equipment Transmission	1,798,900,000	1,772,300,000
Public Utilities Property Plant And Equipment Generation Or Processing	0	0
Public Utilities Property Plant And Equipment Plant In Service	6,553,300,000	6,467,000,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-1,700,600,000	-1,631,300,000
Property Plant And Equipment Net Excluding Construction Work In Progress	4,852,700,000	4,835,700,000
Public Utilities Property Plant And Equipment Construction Work In Progress	294,500,000	208,200,000
Property, Plant and Equipment, Net	5,147,239,000	5,043,887,000
Public Service Company Of New Hampshire [Member]	'	'
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	1,629,100,000	1,608,200,000
Public Utilities Property Plant And Equipment Transmission	713,500,000	695,700,000
Public Utilities Property Plant And Equipment Generation Or Processing	1,134,000,000	1,131,200,000
Public Utilities Property Plant And Equipment Plant In Service	3,476,600,000	3,435,100,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-1,045,300,000	-1,021,800,000
Property Plant And Equipment Net Excluding Construction Work In Progress	2,431,300,000	2,413,300,000
Public Utilities Property Plant And Equipment Construction Work In Progress	88,600,000	54,300,000
Property, Plant and Equipment, Net	2,519,921,000	2,467,556,000
Western Massachusetts Electric Company [Member]	'	'
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	766,300,000	756,600,000
Public Utilities Property Plant And Equipment Transmission	841,100,000	826,400,000
Public Utilities Property Plant And Equipment Generation Or Processing	33,900,000	21,100,000
Public Utilities Property Plant And Equipment Plant In Service	1,641,300,000	1,604,100,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-283,700,000	-271,500,000
Property Plant And Equipment Net Excluding Construction Work In Progress	1,357,600,000	1,332,600,000
Public Utilities Property Plant And Equipment Construction Work In Progress	61,100,000	48,500,000
Property, Plant and Equipment, Net	$1,418,673,000	$1,381,060,000

DERIVATIVE_INSTURMENTS_Details

DERIVATIVE INSTURMENTS (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Liabilities, Noncurrent	($449,439,000)	'	($449,439,000)	'	($624,050,000)
Other Derivatives Not Designated As Hedging Instruments At Fair Value Net Total Abstract	'	'	'	'	'
Description of Derivative Activity Volume	'	'	'Commodity Supply and Price Risk Management: As required by regulation, CL&P, along with UI, has capacity-related contracts with generation facilities. CL&P has a sharing agreement with UI, with 80 percent of each contract allocated to CL&P and 20 percent allocated to UI. The combined capacity of these contracts is 787 MW. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the forward capacity market price received in the ISO-NE capacity markets. In addition, CL&P has a contract to purchase 0.1 million MWh of energy per year through 2020. NSTAR Electric has a renewable energy contract to purchase 0.1 million MWh of energy per year through 2018 and a capacity-related contract to purchase up to 35 MW per year through 2019. As of June 30, 2014 and December 31, 2013, NU had NYMEX future contracts in order to reduce variability associated with the purchase price of approximately 6.6 million and 9.1 million MMBtu of natural gas, respectively.	'	'
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net Abstract	'	'	'	'	'
Derivative Gain Loss On Derivative Net	'	500,000	'	800,000	'
Derivative Instruments Gain Loss Recognized In Regulatory Asset Liability	111,600,000	22,200,000	166,000,000	50,100,000	'
Derivative Credit Risk Related Contingent Features Abstract	'	'	'	'	'
Additional Collateral Aggregate Fair Value	600,000	'	600,000	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsExitPricePremium	'	'	'Exit price premiums of 8 percent through 25 percent are also applied on these contracts and reflect the most recent market activity available for similar type contracts.	'	'
The Connecticut Light And Power Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Liabilities - Current	-85,611,000	'	-85,611,000	'	-92,233,000
Derivative Liabilities, Noncurrent	-445,342,000	'	-445,342,000	'	-617,072,000
Fair Value Inputs Level 2 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	300,000	'	300,000	'	1,600,000
Derivative Liabilities - Current	-500,000	'	-500,000	'	'
Derivative Assets Noncurrent	'	'	'	'	200,000
Fair Value Inputs Level 3 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	11,600,000	'	11,600,000	'	8,600,000
Derivative Liabilities - Current	-87,800,000	'	-87,800,000	'	-93,700,000
Derivative Liabilities, Noncurrent	-449,400,000	'	-449,400,000	'	-624,100,000
Derivative Assets Noncurrent	94,700,000	'	94,700,000	'	74,000,000
Fair Value Inputs Level 3 [Member] | MinimumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	3.13	'	3.13	'	5.07
FairValueInputsEnergyPrices	63	'	63	'	49
FairValueInputsRenewableEnergyCreditPrices	38	'	38	'	36
FairValueInputsForwardReserve	3.3	'	3.3	'	3.3
Fair Value Inputs Level 3 [Member] | MaximumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	13	'	13	'	11.82
FairValueInputsEnergyPrices	66	'	66	'	77
FairValueInputsRenewableEnergyCreditPrices	70	'	70	'	87
FairValueInputsForwardReserve	9.5	'	9.5	'	3.3
Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	11,600,000	'	11,600,000	'	7,300,000
Derivative Liabilities - Current	-85,600,000	'	-85,600,000	'	-92,200,000
Derivative Liabilities, Noncurrent	-445,300,000	'	-445,300,000	'	-617,100,000
Derivative Assets Noncurrent	94,700,000	'	94,700,000	'	71,400,000
Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member] | MinimumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	7	'	7	'	5.07
FairValueInputsEnergyPrices	63	'	63	'	56
FairValueInputsForwardReserve	3.3	'	3.3	'	3.3
Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member] | MaximumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	13	'	13	'	10.42
FairValueInputsEnergyPrices	66	'	66	'	58
FairValueInputsForwardReserve	9.5	'	9.5	'	3.3
Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	'	'	'	'	1,200,000
Derivative Liabilities - Current	-2,200,000	'	-2,200,000	'	-1,500,000
Derivative Liabilities, Noncurrent	-4,100,000	'	-4,100,000	'	-7,000,000
Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member] | MinimumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	3.13	'	3.13	'	5.07
FairValueInputsRenewableEnergyCreditPrices	38	'	38	'	36
Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member] | MaximumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	11.13	'	11.13	'	7.38
FairValueInputsRenewableEnergyCreditPrices	70	'	70	'	70
Netting And Collateral [Member] | Fair Value Inputs Level 2 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	-100,000	'	-100,000	'	-300,000
Derivative Liabilities - Current	200,000	'	200,000	'	'
Netting And Collateral [Member] | Fair Value Inputs Level 3 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	-4,800,000	'	-4,800,000	'	-9,800,000
Derivative Assets Noncurrent	-17,000,000	'	-17,000,000	'	-42,200,000
Netting And Collateral [Member] | Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	-4,800,000	'	-4,800,000	'	-9,800,000
Derivative Assets Noncurrent	-17,000,000	'	-17,000,000	'	-42,200,000
Commodity [Member] | Fair Value Inputs Level 2 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	400,000	'	400,000	'	1,900,000
Derivative Liabilities - Current	-700,000	'	-700,000	'	'
Derivative Assets Noncurrent	'	'	'	'	200,000
Commodity [Member] | Fair Value Inputs Level 3 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	16,400,000	'	16,400,000	'	18,400,000
Derivative Liabilities - Current	-87,800,000	'	-87,800,000	'	-93,700,000
Derivative Liabilities, Noncurrent	-449,400,000	'	-449,400,000	'	-624,100,000
Derivative Assets Noncurrent	111,700,000	'	111,700,000	'	116,200,000
Commodity [Member] | Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	16,400,000	'	16,400,000	'	17,100,000
Derivative Liabilities - Current	-85,600,000	'	-85,600,000	'	-92,200,000
Derivative Liabilities, Noncurrent	-445,300,000	'	-445,300,000	'	-617,100,000
Derivative Assets Noncurrent	111,700,000	'	111,700,000	'	113,600,000
Commodity [Member] | Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	'	'	'	'	1,200,000
Derivative Liabilities - Current	-2,200,000	'	-2,200,000	'	-1,500,000
Derivative Liabilities, Noncurrent	($4,100,000)	'	($4,100,000)	'	($7,000,000)

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	($564.30)	($833.10)	($635.20)	($878.60)
Net Realized/Unrealized Gains Losses included in Net Income	0	1.3	'	7.1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability	111.8	22.7	161.3	48.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	21.6	21	43	34.5
Ending Balance	-430.9	-788.1	-430.9	-788.1
The Connecticut Light And Power Company [Member]	'	'	'	'
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	-557	-819.6	-630.6	-866.2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability	112.2	21.9	164.5	46.3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	20.2	21.9	41.5	44.1
Ending Balance	-424.6	-775.8	-424.6	-775.8
NSTAR Electric Company [Member]	'	'	'	'
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	-7.3	-13.6	-7.3	-14.9
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability	-0.4	-0.5	-0.5	0.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	1.4	1	1.5	1.6
Ending Balance	($6.30)	($13.10)	($6.30)	($13.10)

MARKETABLE_SECURITIES_Details

MARKETABLE SECURITIES (Details) (USD $)

3 Months Ended

6 Months Ended

6 Months Ended

12 Months Ended

6 Months Ended

12 Months Ended

6 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2014

Dec. 31, 2013

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

US Government Debt Securities Member

US Government Debt Securities Member

US Government Debt Securities Member

US Government Debt Securities Member

Corporate Bond Securities Member

Corporate Bond Securities Member

Corporate Bond Securities Member

Corporate Bond Securities Member

Asset Backed Securities Member

Asset Backed Securities Member

Asset Backed Securities Member

Asset Backed Securities Member

Municipal Bonds Member

Municipal Bonds Member

Municipal Bonds Member

Municipal Bonds Member

Other Debt Securities Member

Other Debt Securities Member

Other Debt Securities Member

Other Debt Securities Member

Cash And Cash Equivalents Member

Cash And Cash Equivalents Member

Cash And Cash Equivalents Member

Cash And Cash Equivalents Member

Mutual Funds [Member]

Mutual Funds [Member]

Debt Securities

Debt Securities

Debt Securities

Debt Securities

Equity Securities

Equity Securities

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 2 [Member]

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Fair Value Inputs Level 1 Member

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Western Massachusetts Electric Company [Member]

Schedule Of Available For Sale Securities [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Of Securities Under Fair Value Option

$59.60

'

$59.60

'

$57.20

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value, Option, Changes in Fair Value, Gain (Loss)

2.2

0.1

2.4

4.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investments, Debt and Equity Securities [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Fair Value Disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

315.3

299.6

58

57.9

230.2

224.1

Available-for-sale Securities, Gross Unrealized Gains

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7.3

2.5

0

0

66.7

60.5

AvailableForSaleSecuritiesGrossUnrealizedLoss

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-0.3

-2.1

0

0

'

'

Available For Sale Securities Amortized Cost

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

308.3

299.2

58

57.9

163.5

163.6

Marketable Securities, Restricted

444.3

'

444.3

'

424

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Fair Value Abstract

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value

57.7

'

57.7

'

'

2.7

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After Ten Years Fair Value

107.2

'

107.2

'

'

4.1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After One Year Through Five Years Fair Value

74.6

'

74.6

'

'

32

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Within One Year Fair Value

75.8

'

75.8

'

'

19.2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Fair Value

315.3

'

315.3

'

'

58

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Amortized Cost Abstract

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost

73.9

'

73.9

'

'

31.9

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Within One Year Amortized Cost

75.9

'

75.9

'

'

19.2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After Ten Years Amortized Cost

102.4

'

102.4

'

'

4.2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost

56.1

'

56.1

'

'

2.7

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Amortized Cost

308.3

'

308.3

'

'

58

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Assets And Liabilities Measured On Recurring Basis Abstract

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investments Fair Value Disclosure

630

'

630

'

580.9

58

57.9

357

314.2

2

10.9

273

266.7

56

47

40.6

61.4

0

6.8

61.8

53.6

15.8

15.1

36.5

30.4

15.2

9

109.5

105.5

11.7

11.2

24.6

15.8

13.3

4.9

42.3

32.9

2

10.9

314.7

281.3

'

'

'

'

'

'

TradingSecuritiesEquity

24.9

'

24.9

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

IncreaseDecreaseInTradingSecurities

$0.90

'

$1.40

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

SHORT_TERM_AND_LONG_TERM_DEBT_

SHORT TERM AND LONG TERM DEBT (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Remaining Borrowing Capacity	$739,500,000	$435,500,000
Line of Credit Facility, Amount Outstanding	710,500,000	1,010,000,000
Short-term Debt, Weighted Average Interest Rate	0.25%	0.24%
Description of commercial paper program	'Effective July 23, 2014, NU parent, CL&P, PSNH, WMECO, NSTAR Gas and Yankee Gas amended their joint $1.45 billion revolving credit facility to extend the expiration date an additional year to September 6, 2019. The revolving credit facility is to be used primarily to backstop NU parent’s $1.45 billion commercial paper program. The commercial paper program allows NU parent to issue commercial paper as a form of short-term debt. As of June 30, 2014 and December 31, 2013, NU had $710.5 million and $1.01 billion, respectively, in short-term borrowings outstanding under the NU parent commercial paper program, leaving $739.5 million and $435.5 million of available borrowing capacity as of June 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of June 30, 2014 and December 31, 2013 was 0.25 percent and 0.24 percent, respectively, which is generally based on A2/P2 rated commercial paper. As of June 30, 2014, there were intercompany loans from NU of $6.4 million to CL&P, $95 million to PSNH and $15.9 million to WMECO. As of December 31, 2013, there were intercompany loans from NU of $287.3 million to CL&P and $86.5 million to PSNH. Effective July 23, 2014, NSTAR Electric amended its $450 million revolving credit facility to extend the expiration date an additional year to September 6, 2019. This facility serves to backstop NSTAR Electric’s existing $450 million commercial paper program. As of June 30, 2014 and December 31, 2013, NSTAR Electric had $194.5 million and $103.5 million, respectively, in short-term borrowings outstanding under its commercial paper program, leaving $255.5 million and $346.5 million of available borrowing capacity as of June 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of June 30, 2014 and December 31, 2013 was 0.16 percent and 0.13 percent, respectively, which is generally based on A2/P1 rated commercial paper.	'
Description of Working Capital	'Working Capital: Each of NU, CL&P, NSTAR Electric, PSNH and WMECO use its available capital resources to fund its respective construction expenditures, meet debt requirements, pay operating costs, including storm-related costs, pay dividends and fund other corporate obligations, such as pension contributions. The current growth in NU’s transmission construction expenditures utilizes a significant amount of cash for projects that have a long-term return on investment and recovery period. In addition, NU’s Regulated companies recover their electric and natural gas distribution construction expenditures as the related project costs are depreciated over the life of the assets. This impacts the timing of the revenue stream designed to fully recover the total investment plus a return on the equity portion of the cost and related financing costs. These factors have resulted in current liabilities exceeding current assets by approximately $730 million, $220 million and $200 million at NU, CL&P and NSTAR Electric, respectively, as of June 30, 2014. As of June 30, 2014, $366.7 million of NU's obligations classified as current liabilities relates to long-term debt that will be paid in the next 12 months, consisting of $312 million for CL&P, $4.7 million at NSTAR Electric and $50 million for PSNH. In addition, $28.9 million relates to the amortization of the purchase accounting fair value adjustment that will be amortized in the next twelve months. NU, with its strong credit ratings, has several options available in the financial markets to repay or refinance these maturities with the issuance of new long-term debt. NU, CL&P, NSTAR Electric, PSNH and WMECO will reduce their short-term borrowings with cash received from operating cash flows or with the issuance of new long-term debt, determined considering capital requirements and maintenance of NU's credit rating and profile. Management expects the future operating cash flows of NU, CL&P, NSTAR Electric, PSNH and WMECO, along with the access to financial markets, will be sufficient to meet any future operating requirements and capital investment forecasted opportunities	'
Notes Payable to Banks	905,000,000	1,093,000,000
Long-term Debt, Description	': On January 2, 2014, Yankee Gas issued $100 million of 4.82 percent Series L First Mortgage Bonds, due to mature in 2044. The proceeds, net of issuance costs, were used to repay the $75 million 4.80 percent Series G First Mortgage Bonds that matured on January 1, 2014 and to pay $25 million in short-term borrowings. In accordance with applicable accounting guidance, these amounts were classified as Long-Term Debt on NU’s balance sheet as of December 31, 2013. On March 7, 2014, NSTAR Electric issued $300 million of 4.40 percent debentures, due to mature in 2044. The proceeds, net of issuance costs, were used to repay the $300 million of 4.875 percent debentures that matured on April 15, 2014. On April 24, 2014, CL&P issued $250 million of 4.30 percent 2014 Series A First Mortgage Bonds, due to mature in April 2044. The proceeds, net of issuance costs, were used to repay short-term borrowings. On July 15, 2014, PSNH repaid at maturity the $50 million of 5.25 percent Series L First Mortgage Bonds using On January 2, 2014, Yankee Gas issued $100 million of 4.82 percent Series L First Mortgage Bonds, due to mature in 2044. The proceeds, net of issuance costs, were used to repay the $75 million 4.80 percent Series G First Mortgage Bonds that matured on January 1, 2014 and to pay $25 million in short-term borrowings. In accordance with applicable accounting guidance, these amounts were classified as Long-Term Debt on NU’s balance sheet as of December 31, 2013. On March 7, 2014, NSTAR Electric issued $300 million of 4.40 percent debentures, due to mature in 2044. The proceeds, net of issuance costs, were used to repay the $300 million of 4.875 percent debentures that matured on April 15, 2014. On April 24, 2014, CL&P issued $250 million of 4.30 percent 2014 Series A First Mortgage Bonds, due to mature in April 2044. The proceeds, net of issuance costs, were used to repay short-term borrowings. On July 15, 2014, PSNH repaid at maturity the $50 million of 5.25 percent Series L First Mortgage Bonds using short-term debt.	'
The Connecticut Light And Power Company [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Notes Payable To Affiliated Companies	6,400,000	287,300,000
NSTAR Electric Company [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Remaining Borrowing Capacity	255,500,000	346,500,000
Line of Credit Facility, Amount Outstanding	'	103,500,000
WeightedAverageDiscountRatePercent	0.16%	0.13%
Notes Payable to Banks	194,500,000	103,500,000
Public Service Company Of New Hampshire [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Notes Payable To Affiliated Companies	95,000,000	86,500,000
Western Massachusetts Electric Company [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Notes Payable To Affiliated Companies	$15,900,000	$0

PENSION_BENEFITS_AND_POSTRETIR1

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	$825,001,000	'	$825,001,000	'	$896,844,000
Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	19,100,000	24,600,000	41,500,000	51,100,000	'
Defined Benefit Plan Interest Cost	56,300,000	51,900,000	113,000,000	103,500,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-77,700,000	-68,600,000	-155,400,000	-139,000,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	31,700,000	52,600,000	64,700,000	105,500,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	1,100,000	1,000,000	2,100,000	2,100,000	'
Defined Benefit Plan Net Periodic Benefit Cost	30,500,000	61,500,000	65,900,000	123,200,000	'
Amount Capitalized Defined Benefit Expense	8,700,000	19,900,000	18,400,000	36,600,000	'
PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	3,200,000	3,700,000	6,300,000	8,500,000	'
Defined Benefit Plan Interest Cost	12,100,000	10,900,000	24,700,000	23,600,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-15,800,000	-13,900,000	-31,600,000	-27,700,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	3,000,000	4,700,000	6,000,000	13,000,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	-700,000	-500,000	-1,400,000	-1,100,000	'
Defined Benefit Plan Net Periodic Benefit Cost	1,800,000	4,900,000	4,000,000	16,300,000	'
Amount Capitalized Defined Benefit Expense	400,000	1,500,000	800,000	5,000,000	'
The Connecticut Light And Power Company [Member]	'	'	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	66,543,000	'	66,543,000	'	95,895,000
The Connecticut Light And Power Company [Member] | Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	5,000,000	6,300,000	10,200,000	12,400,000	'
Defined Benefit Plan Interest Cost	12,400,000	12,100,000	25,700,000	24,200,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-18,700,000	-18,400,000	-38,000,000	-36,900,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	8,200,000	13,900,000	17,300,000	28,000,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	500,000	500,000	900,000	900,000	'
Defined Benefit Plan Net Periodic Benefit Cost	7,400,000	14,400,000	16,100,000	28,600,000	'
Related Intercompany Allocationsof Defined Benefit Expense	7,500,000	11,300,000	14,300,000	22,100,000	'
Amount Capitalized Defined Benefit Expense	4,400,000	7,000,000	9,300,000	14,000,000	'
The Connecticut Light And Power Company [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	500,000	900,000	1,100,000	1,700,000	'
Defined Benefit Plan Interest Cost	1,900,000	2,000,000	4,000,000	3,900,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-2,500,000	-2,500,000	-5,200,000	-5,000,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	1,000,000	1,900,000	2,100,000	3,700,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	'	'	0	'	'
Defined Benefit Plan Net Periodic Benefit Cost	900,000	2,300,000	2,000,000	4,300,000	'
Related Intercompany Allocationsof Defined Benefit Expense	1,100,000	1,900,000	2,200,000	3,600,000	'
Amount Capitalized Defined Benefit Expense	500,000	1,200,000	1,000,000	2,400,000	'
NSTAR Electric Company [Member]	'	'	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	150,151,000	'	150,151,000	'	118,010,000
NSTAR Electric Company [Member] | Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	3,000,000	7,300,000	7,600,000	16,500,000	'
Defined Benefit Plan Interest Cost	10,300,000	14,700,000	20,600,000	29,000,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-15,700,000	-20,200,000	-31,500,000	-42,200,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	5,900,000	14,600,000	11,700,000	29,100,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	0	-100,000	0	-100,000	'
Defined Benefit Plan Net Periodic Benefit Cost	3,500,000	16,300,000	8,400,000	32,300,000	'
Related Intercompany Allocationsof Defined Benefit Expense	1,400,000	-2,200,000	3,800,000	-4,100,000	'
Amount Capitalized Defined Benefit Expense	1,000,000	6,500,000	2,900,000	11,800,000	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Defined Benefit Plan, Funded Status of Plan	85,800,000	'	85,800,000	'	118,000,000
NSTAR Electric Company [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	800,000	'	1,600,000	'	'
Defined Benefit Plan Interest Cost	4,800,000	'	9,700,000	'	'
Defined Benefit Plan, Expected Return on Plan Assets	-6,500,000	'	-13,000,000	'	'
Defined Benefit Plan, Amortization of Gains (Losses)	-200,000	'	-300,000	'	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	-500,000	'	-900,000	'	'
Defined Benefit Plan Net Periodic Benefit Cost	-1,600,000	-2,000,000	-2,900,000	2,300,000	'
Related Intercompany Allocationsof Defined Benefit Expense	0	'	100,000	'	'
Amount Capitalized Defined Benefit Expense	-500,000	'	-1,000,000	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Defined Benefit Plan, Funded Status of Plan	61,200,000	'	61,200,000	'	'
NSTAR Electric Company [Member] | Supplemental Employee Retirement Plans, Defined Benefit [Member]	'	'	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	400,000	'	400,000	'	'
Defined Benefit Plan, Funded Status of Plan	3,600,000	'	3,600,000	'	'
Public Service Company Of New Hampshire [Member]	'	'	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	15,055,000	'	15,055,000	'	15,272,000
Public Service Company Of New Hampshire [Member] | Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	2,300,000	3,200,000	5,100,000	6,500,000	'
Defined Benefit Plan Interest Cost	5,800,000	5,900,000	12,300,000	11,900,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-9,300,000	-9,200,000	-19,500,000	-16,800,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	2,800,000	5,400,000	6,000,000	10,800,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	100,000	100,000	300,000	300,000	'
Defined Benefit Plan Net Periodic Benefit Cost	1,700,000	5,400,000	4,200,000	12,700,000	'
Related Intercompany Allocationsof Defined Benefit Expense	2,100,000	2,600,000	4,200,000	5,200,000	'
Amount Capitalized Defined Benefit Expense	800,000	1,700,000	1,700,000	3,900,000	'
Public Service Company Of New Hampshire [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	300,000	600,000	700,000	1,100,000	'
Defined Benefit Plan Interest Cost	1,000,000	1,000,000	2,100,000	2,000,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-1,300,000	-1,300,000	-2,700,000	-2,600,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	600,000	900,000	1,100,000	1,800,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	'	'	0	'	'
Defined Benefit Plan Net Periodic Benefit Cost	600,000	1,200,000	1,200,000	2,300,000	'
Related Intercompany Allocationsof Defined Benefit Expense	300,000	400,000	600,000	800,000	'
Amount Capitalized Defined Benefit Expense	200,000	400,000	400,000	700,000	'
Western Massachusetts Electric Company [Member]	'	'	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	2,805,000	'	2,805,000	'	3,911,000
Western Massachusetts Electric Company [Member] | Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	800,000	1,200,000	1,900,000	2,400,000	'
Defined Benefit Plan Interest Cost	2,500,000	2,500,000	5,200,000	5,000,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-4,400,000	-4,400,000	-9,000,000	-8,700,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	1,700,000	2,900,000	3,500,000	5,900,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	100,000	100,000	200,000	200,000	'
Defined Benefit Plan Net Periodic Benefit Cost	700,000	2,300,000	1,800,000	4,800,000	'
Related Intercompany Allocationsof Defined Benefit Expense	1,400,000	2,000,000	2,700,000	4,000,000	'
Amount Capitalized Defined Benefit Expense	600,000	1,300,000	1,400,000	2,600,000	'
Western Massachusetts Electric Company [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	100,000	200,000	200,000	400,000	'
Defined Benefit Plan Interest Cost	400,000	400,000	800,000	800,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-600,000	-600,000	-1,100,000	-1,200,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	100,000	300,000	200,000	600,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	'	'	0	'	'
Defined Benefit Plan Net Periodic Benefit Cost	0	300,000	100,000	600,000	'
Related Intercompany Allocationsof Defined Benefit Expense	200,000	300,000	400,000	600,000	'
Amount Capitalized Defined Benefit Expense	$0	$200,000	$100,000	$400,000	'

Environmental_Matters_Details

Environmental Matters (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Site Contingency [Line Items]	'	'
Environmental Site Quantity	66	68
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	$35.40	'
Ending Balance	34.5	35.4
MGP Site accrual [Member]	'	'
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Ending Balance	29.8	31.4
The Connecticut Light And Power Company [Member]	'	'
Site Contingency [Line Items]	'	'
Environmental Site Quantity	17	18
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	3.4	'
Ending Balance	4.2	3.4
NSTAR Electric Company [Member]	'	'
Site Contingency [Line Items]	'	'
Environmental Site Quantity	14	12
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	1.2	'
Ending Balance	1.2	1.2
Public Service Company Of New Hampshire [Member]	'	'
Site Contingency [Line Items]	'	'
Environmental Site Quantity	13	15
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	5.4	'
Ending Balance	5.3	5.4
Western Massachusetts Electric Company [Member]	'	'
Site Contingency [Line Items]	'	'
Environmental Site Quantity	5	5
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	0.4	'
Ending Balance	$0.60	$0.40

LongTerm_Contractual_Arrangeme1

Long-Term Contractual Arrangements (Details) (Renewable Energy Contracts [Member], USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
NSTAR Electric Company [Member]	'
Long-term Purchase Commitment [Line Items]	'
Unrecorded Unconditional Purchase Obligation, Due within One Year	$43.60
Unrecorded Unconditional Purchase Obligation, Due within Two Years	86.3
Unrecorded Unconditional Purchase Obligation, Due within Three Years	93.7
Unrecorded Unconditional Purchase Obligation, Due within Four Years	89.8
Unrecorded Unconditional Purchase Obligation, Due within Five Years	53.3
Unrecorded Unconditional Purchase Obligation, Due after Five Years	302.8
Unrecorded Unconditional Purchase Obligation, Total	669.5
Western Massachusetts Electric Company [Member]	'
Long-term Purchase Commitment [Line Items]	'
Unrecorded Unconditional Purchase Obligation, Due within One Year	0
Unrecorded Unconditional Purchase Obligation, Due within Two Years	0
Unrecorded Unconditional Purchase Obligation, Due within Three Years	2.4
Unrecorded Unconditional Purchase Obligation, Due within Four Years	2.4
Unrecorded Unconditional Purchase Obligation, Due within Five Years	2.4
Unrecorded Unconditional Purchase Obligation, Due after Five Years	28.9
Unrecorded Unconditional Purchase Obligation, Total	$36.10

Deferred_Contractual_Obligatio

Deferred Contractual Obligations (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Loss Contingency, Information about Litigation Matters [Abstract]	'	'
Court of Federal Claims Ruling To CYAPC	'	$126.30
Court Of Federal Claims Ruling To YAEC	'	73.3
Trial Court Ruling To MYAPC	'	35.8
Connecticut Yankee Proceeds Received	126.3	'
Yankee Atomic Proceeds Received	73.3	'
Maine Yankee Proceeds Received	$35.80	'

Guarantees_and_Indemnification1

Guarantees and Indemnifications (Details) (USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Guarantee Of Financial Obligations Of Npt [Member]	'
Guarantee Obligations [Line Items]	'
Guarantee Obligations Maximum Exposure	$25
Various Subsidiary Surety Bonds And Performance Guarantees Expiring Between 2014 And 2016 [Member]	'
Guarantee Obligations [Line Items]	'
Guarantee Obligations Maximum Exposure	67
Guarantee Of Rocky River Reality And Nusco Lease Payments For Real Estate And Vehicles Expiring 2019 Through 2024 [Member]	'
Guarantee Obligations [Line Items]	'
Guarantee Obligations Maximum Exposure	16
Guarantee Of Debt Of Ne Hydros [Member]	'
Guarantee Obligations [Line Items]	'
Guarantee Obligations Maximum Exposure	$2.50

Other_Contingencies_Details

Other Contingencies (Details) (Unfavorable Regulatory Action [Member])	6 Months Ended
	Jun. 30, 2014
Unfavorable Regulatory Action [Member]	'
Loss Contingencies Line Items	'
Loss Contingency, Description	'        FERC Base ROE Complaints On September 30, 2011, a complaint was filed jointly at FERC under Sections 206 and 306 of the Federal Power Act by several New England state attorneys general, state regulatory commissions, consumer advocates and other parties (the “Complainants”). The Complainants alleged that the base ROE of 11.14 percent that has been utilized since 2006 in the calculation of formula rates for transmission service under the ISO-NE Open Access Transmission Tariff by NETOs, including CL&P, NSTAR Electric, PSNH and WMECO, was unjust and unreasonable and asserted that the rate was excessive due to changes in the capital markets. Complainants sought an order to reduce the base ROE, effective October 1, 2011, and to require refunds. The FERC set the case for trial before a FERC ALJ after settlement negotiations were unsuccessful in August 2012. On August 6, 2013, the FERC ALJ issued an initial decision finding that the base ROE in effect from October 1, 2011 through December 31, 2012 (refund period) was not reasonable, and recommended separate base ROEs for the refund period of 10.6 percent and for the period beginning when FERC issues its final decision (prospective period) of 9.7 percent, leaving policy considerations and additional adjustments to the FERC. In the third quarter of 2013, the Company recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact from the FERC ALJ's initial decision for the refund period. The aggregate after-tax charge to third quarter 2013 earnings totaled $14.3 million at NU, which represented reserves of $7.7 million at CL&P, $3.4 million at NSTAR Electric, $1.4 million at PSNH and $1.8 million at WMECO. On June 19, 2014, FERC issued an order partially affirming and partially reversing the ALJ’s initial decision. FERC set a single tentative base ROE of 10.57 percent for the refund period and prospective period. FERC also modified its traditional methodology by adopting a two-step discounted cash flow analysis that it utilizes to determine the ROEs of both natural gas and oil pipeline projects. Using this methodology, FERC determined a new zone of reasonableness of 7.03 percent to 11.74 percent, and set the tentative base ROE at the 75th percentile of this new zone. FERC also stated that a utility’s total ROE inclusive of transmission incentive ROE adders, should not exceed the top of the new zone of reasonableness produced by this methodology. FERC instituted a paper hearing on the long-term growth rate portion of the methodology, before it issues a final determination on the base ROE. On July 21, 2014, the NETOs and Complainants filed rehearing requests in this proceeding. On December 27, 2012, a second complaint was filed jointly at FERC by several additional consumer groups and municipal parties, which challenged the NETOs’ base ROE and sought refunds for the 15-month period beginning January 1, 2013. On June 19, 2014, the FERC issued a second order finding that the complaint raised issues of material fact, and set this complaint for trial, should settlement negotiations be unsuccessful. FERC stated that it could issue an order in this case by mid-2016. On July 21, 2014, the NETOs filed a rehearing request in this proceeding. Though NU cannot predict the ultimate outcome of this proceeding, in the second quarter of 2014, the Company recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact from the FERC’s two orders issued on June 19, 2014 for the two refund periods. The aggregate after-tax charge to second quarter 2014 earnings totaled $32.1 million at NU, which represented reserves of $18.5 million at CL&P, $6.1 million at NSTAR Electric, $2 million at PSNH and $5.5 million at WMECO. As of June 30, 2014, the cumulative pre-tax reserves totaled $79.3 million at NU, $44.7 million at CL&P, $16.2 million at NSTAR Electric, $6.2 million at PSNH and $12.2 million at WMECO. As of December 31, 2013, the pre-tax reserves totaled $24.6 million at NU, $13.3 million at CL&P, $5.9 million at NSTAR Electric, $2.4 million at PSNH and $3 million at WMECO. The reserves were recorded in each electric subsidiary's respective transmission regulatory tracker mechanism and as a reduction of operating revenues. See Note 2, “Regulatory Accounting” for further information. On July 31, 2014, the Complainants filed an additional complaint with FERC. At this time, the Company cannot determine the outcome of this complaint. F.         CPSL Since 2006, NSTAR Electric has been recovering incremental costs related to the DPU-approved Safety and Reliability Programs. From 2006 through 2011, cumulative costs associated with the CPSL program resulted in an incremental revenue requirement to customers of approximately $83 million. These amounts included incremental operations and maintenance costs and the related revenue requirement for specific capital investments relative to the CPSL programs. On May 28, 2010, the DPU issued an order on NSTAR Electric’s 2006 CPSL cost recovery filing (the May 2010 Order). In October 2010, NSTAR Electric filed a reconciliation of the cumulative CPSL program activity for the periods 2006 through 2009 with the DPU in order to determine a proposed rate adjustment. The DPU allowed the proposed rates to go into effect January 1, 2011, subject to final reconciliation of CPSL program costs through a future DPU proceeding. In February 2013, NSTAR Electric updated the October 2010 filing with final activity through 2011. NSTAR Electric recorded its 2006 through 2011 revenues under the CPSL programs based on the May 2010 Order. NSTAR Electric cannot predict the timing of a final DPU order related to its CPSL filings for the period 2006 through 2011. While management does not believe that any subsequent DPU order would result in revenues that are materially different than the amounts already recognized, it is reasonably possible that an order could have a material impact on NSTAR Electric’s results of operations, financial position and cash flows. G.        Basic Service Bad Debt Adder In accordance with a generic DPU order, electric utilities in Massachusetts recover the energy-related portion of bad debt costs in their Basic Service rates. In 2007, NSTAR Electric filed its 2006 Basic Service reconciliation with the DPU proposing an adjustment related to the increase of its Basic Service bad debt charge-offs. The DPU issued an order approving the implementation of a revised Basic Service rate but instructed NSTAR Electric to reduce distribution rates by an amount equal to the increase in its Basic Service bad debt charge-offs. This adjustment to NSTAR Electric’s distribution rates would eliminate the fully reconciling nature of the Basic Service bad debt adder. In 2010, NSTAR Electric filed an appeal of the DPU’s order with the SJC. In 2012, the SJC vacated the DPU order and remanded the matter to the DPU for further review. The DPU has not taken any action on the remand. NSTAR Electric deferred approximately $34 million of costs associated with energy-related bad debt as a regulatory asset through 2011 as NSTAR Electric had concluded that it was probable that these costs would ultimately be recovered from customers. Due to the delays and the duration of the proceedings, NSTAR Electric concluded that while an ultimate outcome on the matter in its favor remained "more likely than not," it could no longer be deemed "probable." As a result, NSTAR Electric recognized a reserve related to the regulatory asset in 2012. NSTAR Electric will continue to maintain the reserve until the proceeding has been concluded with the DPU.

FAIR_VALUE_OF_FINANCIAL_INSTRU2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	$155,568,000	$155,568,000
Carrying Reported Amount Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	155,600,000	155,600,000
Other Long Term Debt	8,542,700,000	8,310,200,000
Estimate Of Fair Value Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	150,100,000	152,700,000
Other Long Term Debt	9,008,400,000	8,443,100,000
The Connecticut Light And Power Company [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	116,200,000	116,200,000
The Connecticut Light And Power Company [Member] | Carrying Reported Amount Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	116,200,000	116,200,000
Other Long Term Debt	2,991,600,000	2,741,200,000
The Connecticut Light And Power Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	110,300,000	110,500,000
Other Long Term Debt	3,344,500,000	2,952,800,000
NSTAR Electric Company [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	43,000,000	43,000,000
NSTAR Electric Company [Member] | Carrying Reported Amount Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	43,000,000	43,000,000
Other Long Term Debt	1,797,400,000	1,801,100,000
NSTAR Electric Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	39,800,000	42,200,000
Other Long Term Debt	1,949,800,000	1,888,000,000
Public Service Company Of New Hampshire [Member] | Carrying Reported Amount Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Other Long Term Debt	1,049,200,000	1,049,000,000
Public Service Company Of New Hampshire [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Other Long Term Debt	1,105,800,000	1,073,900,000
Western Massachusetts Electric Company [Member] | Carrying Reported Amount Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Other Long Term Debt	628,900,000	629,400,000
Western Massachusetts Electric Company [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]	'	'
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]	'	'
Other Long Term Debt	$665,300,000	$640,100,000

ACCUMULATED_OTHER_COMPREHENSIV2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
AOCI Cash Flow Hedging Component [Abstract]	'	'	'	'
Beginning Balance -AOCI From CF Hedges Effect Net Of Tax	'	'	($14,400,000)	($16,400,000)
OCI Amortization of Cash Flow Hedge, Net of Tax	500,000	500,000	1,000,000	1,000,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	510,000	514,000	1,019,000	1,030,000
Ending Balance - AOCI From CFHedges Effect Net Of Tax	-13,400,000	-15,400,000	-13,400,000	-15,400,000
AOCI Unrealized GainLoss component [Abstract]	'	'	'	'
AOCI Unrealized Gains/Losses on Other Securities	'	'	400,000	1,300,000
OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsNetOfTax	'	'	500,000	-700,000
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	218,000	-591,000	458,000	-772,000
AOCI Unrealized Gains/Losses on Other Securities-Ending Balance	900,000	600,000	900,000	600,000
AOCI Defined Benefit Component [Abstract]	'	'	'	'
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	'	'	-32,000,000	-57,800,000
Reclassification of DB Plans	700,000	1,500,000	1,800,000	3,100,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	2,086,000	1,506,000	3,047,000	3,127,000
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	-29,000,000	-54,700,000	-29,000,000	-54,700,000
Losses arising before reclassification	1,200,000	'	1,200,000	'
AOCI Rollforward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-46,031,000	-72,900,000
AmountReclassifiedFromAOCI	1,200,000	2,000,000	2,800,000	4,100,000
OtherComprehensiveIncomeBeforeReclassifications	'	'	1,700,000	-700,000
Other Comprehensive Income (Loss), Net of Tax, Total	2,814,000	1,429,000	4,524,000	3,385,000
AOCI ending Balance	-41,507,000	-69,500,000	-41,507,000	-69,500,000
Reclassication of Items out of AOCI [Abstract]	'	'	'	'
OCI Reclass CF Hedging Tax	300,000	300,000	700,000	700,000
OCI Amortization of Cash Flow Hedges, Before Tax	-800,000	-800,000	-1,700,000	-1,700,000
OCI Amortization of Cash Flow Hedge, Net of Tax	-500,000	-500,000	-1,000,000	-1,000,000
OCI Amortization of Prior Service Cost	'	'	-100,000	-100,000
Amortization of actuarial gain or loss	-1,200,000	-2,200,000	-2,900,000	-4,700,000
OCI Defined Benefit Plan Adjustment Before Tax	-1,200,000	-2,200,000	-3,000,000	-4,800,000
OCI Defined Benefit Plan Tax	500,000	700,000	1,200,000	1,700,000
Reclassification of DB Plans	-700,000	-1,500,000	-1,800,000	-3,100,000
AmountReclassifiedFromAOCI	-1,200,000	-2,000,000	-2,800,000	-4,100,000
The Connecticut Light And Power Company [Member]	'	'	'	'
AOCI Cash Flow Hedging Component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111,000	111,000	222,000	222,000
AOCI Unrealized GainLoss component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	7,000	-20,000	15,000	-26,000
AOCI Rollforward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-1,387,000	'
Other Comprehensive Income (Loss), Net of Tax, Total	118,000	91,000	237,000	196,000
AOCI ending Balance	-1,150,000	'	-1,150,000	'
Public Service Company Of New Hampshire [Member]	'	'	'	'
AOCI Cash Flow Hedging Component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	291,000	291,000	581,000	582,000
AOCI Unrealized GainLoss component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	12,000	-34,000	26,000	-45,000
AOCI Defined Benefit Component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	0	0	0	-3,000
AOCI Rollforward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-8,550,000	'
Other Comprehensive Income (Loss), Net of Tax, Total	303,000	257,000	607,000	534,000
AOCI ending Balance	-7,943,000	'	-7,943,000	'
Western Massachusetts Electric Company [Member]	'	'	'	'
AOCI Cash Flow Hedging Component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	84,000	84,000	169,000	169,000
AOCI Unrealized GainLoss component [Abstract]	'	'	'	'
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	2,000	-6,000	4,000	-8,000
AOCI Rollforward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-3,517,000	'
Other Comprehensive Income (Loss), Net of Tax, Total	86,000	78,000	173,000	161,000
AOCI ending Balance	($3,344,000)	'	($3,344,000)	'

COMMON_SHARES_Details

COMMON SHARES (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Class Of Stock [Line Items]	'	'
Common Stock Par Or Stated Value Per Share	$5	$5
Common Stock Shares Authorized	380,000,000	380,000,000
Common Stock Shares Issued	333,327,485	333,113,492
Treasury Stock Shares	17,108,131	17,796,672
Common Stock, Shares, Outstanding	316,219,354	315,273,559
The Connecticut Light And Power Company [Member]	'	'
Class Of Stock [Line Items]	'	'
Common Stock Par Or Stated Value Per Share	$10	$10
Common Stock Shares Authorized	24,500,000	24,500,000
Common Stock Shares Issued	6,035,205	6,035,205
NSTAR Electric Company [Member]	'	'
Class Of Stock [Line Items]	'	'
Common Stock Par Or Stated Value Per Share	$1	$1
Common Stock Shares Authorized	100,000,000	100,000,000
Common Stock Shares Issued	100	100
Public Service Company Of New Hampshire [Member]	'	'
Class Of Stock [Line Items]	'	'
Common Stock Par Or Stated Value Per Share	$1	$1
Common Stock Shares Authorized	100,000,000	100,000,000
Common Stock Shares Issued	301	301
Western Massachusetts Electric Company [Member]	'	'
Class Of Stock [Line Items]	'	'
Common Stock Par Or Stated Value Per Share	$25	$25
Common Stock Shares Authorized	1,072,471	1,072,471
Common Stock Shares Issued	434,653	434,653

COMMON_SHAREHOLDER_EQUIT_AND_N

COMMON SHAREHOLDER EQUIT AND NCI (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Shareholders' Equity, Beginning Balance	'	'	$9,611,528,000	'
Net Income	129,247,000	173,064,000	367,083,000	403,032,000
Dividends on Common Shares	'	'	0	'
Issuance of Common Shares	'	'	0	'
Other Transcations, Net	0	'	0	'
Net Income Attributable to Noncontrolling Interests	1,880,000	2,043,000	3,759,000	3,922,000
Other Comprehensive Income (Loss), Net of Tax	2,814,000	1,429,000	4,524,000	3,385,000
Shareholders' Equity, Ending Balance	9,753,807,000	'	9,753,807,000	'
Common Shareholders Equity [Member]	'	'	'	'
Shareholders' Equity, Beginning Balance	9,723,900,000	9,345,200,000	9,611,500,000	9,237,100,000
Net Income	129,200,000	173,100,000	367,100,000	403,000,000
Dividends on Common Shares	-124,100,000	-115,600,000	-247,900,000	-232,100,000
Dividends, Preferred Stock	-1,900,000	-2,000,000	-3,800,000	-3,900,000
Issuance of Common Shares	200,000	300,000	5,400,000	8,800,000
Other Transcations, Net	23,700,000	4,200,000	17,000,000	-9,700,000
Net Income Attributable to Noncontrolling Interests	'	'	0	0
Other Comprehensive Income (Loss), Net of Tax	2,800,000	1,400,000	4,500,000	3,400,000
Shareholders' Equity, Ending Balance	9,753,800,000	9,406,600,000	9,753,800,000	9,406,600,000
Noncontrolling Interest Member	'	'	'	'
Net Income	'	'	'	0
Dividends on Common Shares	'	'	'	0
Issuance of Common Shares	'	'	'	0
Other Transcations, Net	'	'	'	0
Preferred Stock Member	'	'	'	'
Shareholders' Equity, Beginning Balance	155,600,000	155,600,000	155,600,000	155,600,000
Net Income	'	'	0	'
Dividends, Preferred Stock	-1,900,000	-2,000,000	-3,800,000	-3,900,000
Net Income Attributable to Noncontrolling Interests	1,900,000	2,000,000	3,800,000	3,900,000
Shareholders' Equity, Ending Balance	$155,600,000	$155,600,000	$155,600,000	$155,600,000

EARNINGS_PER_SHARE_Details

EARNINGS PER SHARE (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Notes To Consolidated Financial Statements [Abstract]	'	'	'	'
Net Income Attributable to Controlling Interests	$127,367	$171,021	$363,324	$399,110
Basic	315,950,510	315,154,130	315,742,511	315,141,956
Weighted Average Number Diluted Shares Outstanding Adjustment	1,162,291	808,489	1,259,950	840,622
Diluted	317,112,801	315,962,619	317,002,461	315,982,578
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	0	0	0	3,150
Basic Earnings Per Common Share	$0.40	$0.54	$1.15	$1.27
Diluted Earnings Per Common Share	$0.40	$0.54	$1.15	$1.26

SEGMENT_INFORMATION_Details

SEGMENT INFORMATION (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	$1,677,614,000	$1,635,862,000	$3,968,204,000	$3,630,885,000	'
Operating Income	293,990,000	350,576,000	761,679,000	769,521,000	'
Total Interest Expense	-92,495,000	-86,850,000	-182,471,000	-163,106,000	'
Other Income/(Loss), Net	5,526,000	4,944,000	7,194,000	12,710,000	'
Income Tax Expense	-77,774,000	-95,606,000	-219,319,000	-216,093,000	'
Net Income	129,247,000	173,064,000	367,083,000	403,032,000	'
Net Income Attributable to Noncontrolling Interests	-1,880,000	-2,043,000	-3,759,000	-3,922,000	'
Net Income Attributable to Controlling Interests	127,367,000	171,021,000	363,324,000	399,110,000	'
Total Assets	27,790,445,000	'	27,790,445,000	'	27,795,537,000
Investments in Property, Plant and Equipment	'	'	724,043,000	700,252,000	'
Electric Distribution Member	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	1,261,800,000	1,221,600,000	2,847,800,000	2,595,800,000	'
Depreciation And Amortization	-89,300,000	-152,200,000	-238,200,000	-329,100,000	'
Operating Expenses, Other	-991,500,000	-883,300,000	-2,202,400,000	-1,888,300,000	'
Operating Income	181,000,000	186,100,000	407,200,000	378,400,000	'
Total Interest Expense	-47,200,000	-43,400,000	-94,600,000	-85,600,000	'
Other Income/(Loss), Net	2,900,000	2,200,000	4,300,000	7,100,000	'
Net Income Attributable to Controlling Interests	83,400,000	91,200,000	195,600,000	190,600,000	'
Total Assets	16,942,500,000	'	16,942,500,000	'	17,260,000,000
Investments in Property, Plant and Equipment	'	'	335,600,000	315,300,000	'
Natural Gas Distribution [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	195,500,000	154,100,000	628,300,000	515,900,000	'
Depreciation And Amortization	-16,900,000	-16,700,000	-34,600,000	-34,100,000	'
Operating Expenses, Other	-166,500,000	-127,000,000	-487,900,000	-394,300,000	'
Operating Income	12,100,000	10,400,000	105,800,000	87,500,000	'
Total Interest Expense	-8,700,000	-8,900,000	-17,100,000	-16,200,000	'
Other Income/(Loss), Net	0	100,000	100,000	300,000	'
Net Income Attributable to Controlling Interests	2,000,000	1,200,000	54,100,000	44,500,000	'
Total Assets	2,753,800,000	'	2,753,800,000	'	2,759,700,000
Investments in Property, Plant and Equipment	'	'	68,600,000	70,900,000	'
Transmission [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	206,900,000	247,900,000	458,900,000	487,400,000	'
Depreciation And Amortization	-37,000,000	-34,500,000	-74,000,000	-66,300,000	'
Operating Expenses, Other	-71,000,000	-63,600,000	-137,300,000	-125,800,000	'
Operating Income	98,900,000	149,800,000	247,600,000	295,300,000	'
Total Interest Expense	-28,800,000	-25,200,000	-54,300,000	-47,100,000	'
Other Income/(Loss), Net	2,700,000	2,800,000	4,200,000	5,500,000	'
Net Income Attributable to Controlling Interests	43,900,000	76,800,000	118,800,000	156,700,000	'
Total Assets	6,934,100,000	'	6,934,100,000	'	6,745,800,000
Investments in Property, Plant and Equipment	'	'	289,300,000	297,400,000	'
Other Segment [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	184,700,000	220,700,000	356,900,000	437,800,000	'
Depreciation And Amortization	-7,700,000	-21,700,000	-14,700,000	-40,800,000	'
Operating Expenses, Other	-174,900,000	-194,900,000	-340,300,000	-392,200,000	'
Operating Income	2,100,000	4,100,000	1,900,000	4,800,000	'
Total Interest Expense	-9,100,000	-10,700,000	-18,700,000	-17,100,000	'
Other Income/(Loss), Net	137,700,000	232,200,000	432,400,000	554,000,000	'
Net Income Attributable to Controlling Interests	133,300,000	232,800,000	424,900,000	555,500,000	'
Total Assets	11,566,600,000	'	11,566,600,000	'	11,842,400,000
Investments in Property, Plant and Equipment	'	'	30,500,000	16,700,000	'
Eliminations Segment [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	-171,300,000	-208,400,000	-323,700,000	-406,000,000	'
Depreciation And Amortization	2,300,000	2,900,000	4,100,000	4,600,000	'
Operating Expenses, Other	168,900,000	205,700,000	318,800,000	404,900,000	'
Operating Income	-100,000	200,000	-800,000	3,500,000	'
Total Interest Expense	1,300,000	1,300,000	2,200,000	2,900,000	'
Other Income/(Loss), Net	-137,800,000	-232,300,000	-433,800,000	-554,200,000	'
Net Income Attributable to Controlling Interests	-135,200,000	-231,000,000	-430,100,000	-548,200,000	'
Total Assets	-10,406,600,000	'	-10,406,600,000	'	-10,812,400,000
Investments in Property, Plant and Equipment	'	'	0	0	'
Total [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	1,677,600,000	1,635,900,000	3,968,200,000	3,630,900,000	'
Depreciation And Amortization	-148,600,000	-222,200,000	-357,400,000	-465,700,000	'
Operating Expenses, Other	-1,235,000,000	-1,063,100,000	-2,849,100,000	-2,395,700,000	'
Operating Income	294,000,000	350,600,000	761,700,000	769,500,000	'
Total Interest Expense	-92,500,000	-86,900,000	-182,500,000	-163,100,000	'
Other Income/(Loss), Net	5,500,000	5,000,000	7,200,000	12,700,000	'
Net Income Attributable to Controlling Interests	127,400,000	171,000,000	363,300,000	399,100,000	'
Total Assets	27,790,400,000	'	27,790,400,000	'	27,795,500,000
Investments in Property, Plant and Equipment	'	'	$724,000,000	$700,300,000	'