Public Service Co Of New Hampshire 10-Q 7 Nov 14 2014 FY Quarterly report Financial data

DOCUMENT_AND_ENTITY_INFORMATIO

DOCUMENT AND ENTITY INFORMATION (USD $)	9 Months Ended
	Sep. 30, 2014	Oct. 31, 2014
Document And Entity [Line Items]	'	'
Entity Registrant Name	'NORTHEAST UTILITIES	'
Document Period End Date	30-Sep-14	'
Document Type	'10-Q	'
Entity Central Index Key	'0000072741	'
Current Fiscal Year End Date	'--12-31	'
Entity Common Stock, Shares Outstanding	'	316,799,371
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 $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets:	'	'
Cash	$41,706	$43,364
Receivables, Net	848,510	765,391
Unbilled Revenues	181,284	224,982
Fuel, Materials and Supplies	333,869	303,233
Regulatory Assets Current	445,962	535,791
Marketable Securities - Current	114,722	92,427
Prepayments and Other Current Assets	135,497	121,861
Total Current Assets	2,101,550	2,087,049
Property, Plant and Equipment, Net	18,254,610	17,576,186
Deferred Debits and Other Assets:	'	'
Regulatory Assets Long Term	3,241,122	3,758,694
Goodwill	3,519,401	3,519,401
Marketable Securities	518,032	488,515
Other Long-Term Assets	347,596	365,692
Total Deferred Debits and Other Assets	7,626,151	8,132,302
Total Assets	27,982,311	27,795,537
Current Liabilities:	'	'
Notes Payable	1,046,961	1,093,000
Long-Term Debt - Current Portion	245,583	533,346
Accounts Payable - Current	608,639	742,251
Regulatory Liability Current	398,985	204,278
Other Liabilities - Current	629,508	702,776
Total Current Liabilities	2,929,676	3,275,651
Deferred Credits and Other Liabilities:	'	'
Accumulated Deferred Income Taxes	4,257,996	4,029,026
Regulatory Liabilities Long-Term	509,889	502,984
Long-Term Derivative Liabilities	420,931	624,050
Accrued Pension, PBOP and SERP	787,550	896,844
Other Long-Term Liabilities	863,164	923,053
Total Deferred Credits and Other Liabilities	6,839,530	6,975,957
Capitalization:	'	'
Long-Term Debt	8,166,985	7,776,833
Noncontrolling Interest in Consolidated Subsidiary:	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	155,568	155,568
Common Shareholders' Equity:	'	'
Common Stock	1,666,767	1,665,351
Capital Surplus, Paid In	6,219,516	6,192,765
Retained Earnings	2,351,421	2,125,980
Accumulated Other Comprehensive Loss	-40,172	-46,031
Treasury Stock	-306,980	-326,537
Common Shareholders' Equity	9,890,552	9,611,528
Total Capitalization	18,213,105	17,543,929
Total Liabilities and Capitalization	27,982,311	27,795,537
The Connecticut Light And Power Company [Member]	'	'
Current Assets:	'	'
Cash	16,294	7,237
Receivables, Net	369,492	319,670
Accounts Receivable from Affiliated Companies	35,276	13,777
Unbilled Revenues	87,806	92,401
Regulatory Assets Current	116,531	150,943
Materials and Supplies	47,086	54,606
Accumulated Deferred Income Tax Asset	52,839	'
Prepaid Taxes	47,429	13,962
Prepayments and Other Current Assets	17,608	39,120
Total Current Assets	790,361	691,716
Property, Plant and Equipment, Net	6,700,798	6,451,259
Deferred Debits and Other Assets:	'	'
Regulatory Assets Long Term	1,369,025	1,663,147
Other Long-Term Assets	178,313	174,380
Total Deferred Debits and Other Assets	1,547,338	1,837,527
Total Assets	9,038,497	8,980,502
Current Liabilities:	'	'
Notes Payable To Affiliated Companies	105,400	287,300
Long-Term Debt - Current Portion	162,000	150,000
Accounts Payable - Current	228,379	201,047
Accounts Payable to Affiliated Companies	46,977	56,531
Obligations to Third Party Suppliers	67,630	73,914
Accrued Taxes	54,652	37,186
Regulatory Liability Current	195,663	93,961
Derivative Liabilities - Current	86,759	92,233
Other Liabilities - Current	107,284	97,530
Total Current Liabilities	1,054,744	1,089,702
Deferred Credits and Other Liabilities:	'	'
Accumulated Deferred Income Taxes	1,581,344	1,510,586
Regulatory Liabilities Long-Term	87,696	93,757
Long-Term Derivative Liabilities	418,137	617,072
Accrued Pension, PBOP and SERP	63,756	95,895
Other Long-Term Liabilities	143,838	163,588
Total Deferred Credits and Other Liabilities	2,294,771	2,480,898
Capitalization:	'	'
Long-Term Debt	2,679,775	2,591,208
Noncontrolling Interest in Consolidated Subsidiary:	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	116,200	116,200
Common Shareholders' Equity:	'	'
Common Stock	60,352	60,352
Capital Surplus, Paid In	1,804,228	1,682,047
Retained Earnings	1,029,473	961,482
Accumulated Other Comprehensive Loss	-1,046	-1,387
Common Shareholders' Equity	2,893,007	2,702,494
Total Capitalization	5,688,982	5,409,902
Total Liabilities and Capitalization	9,038,497	8,980,502
NSTAR Electric Company [Member]	'	'
Current Assets:	'	'
Cash	11,040	8,021
Receivables, Net	275,902	209,711
Accounts Receivable from Affiliated Companies	47,215	27,264
Unbilled Revenues	39,372	41,368
Fuel, Materials and Supplies	65,073	44,236
Regulatory Assets Current	128,205	204,144
Prepayments and Other Current Assets	11,267	36,710
Total Current Assets	578,074	571,454
Property, Plant and Equipment, Net	5,211,681	5,043,887
Deferred Debits and Other Assets:	'	'
Regulatory Assets Long Term	998,030	1,235,156
Other Long-Term Assets	62,644	60,624
Total Deferred Debits and Other Assets	1,060,674	1,295,780
Total Assets	6,850,429	6,911,121
Current Liabilities:	'	'
Notes Payable	159,500	103,500
Long-Term Debt - Current Portion	4,700	301,650
Accounts Payable - Current	128,056	202,100
Accounts Payable to Affiliated Companies	62,625	75,707
Obligations to Third Party Suppliers	37,298	'
Power Contract Obligation	35,783	30,842
Renewable Portfolio Standards Compliance Obligation	34,905	39,686
Accrued Taxes	42,338	7,946
Deferred Tax Liabilities Current	9,622	50,128
Regulatory Liability Current	97,215	53,958
Other Liabilities - Current	62,436	39,936
Total Current Liabilities	674,478	910,912
Deferred Credits and Other Liabilities:	'	'
Accumulated Deferred Income Taxes	1,425,306	1,466,835
Regulatory Liabilities Long-Term	266,524	253,108
Accrued Pension, PBOP and SERP	142,249	118,010
Other Long-Term Liabilities	112,853	142,214
Due To Related Parties Noncurrent	0	64,172
Total Deferred Credits and Other Liabilities	1,946,932	2,044,339
Capitalization:	'	'
Long-Term Debt	1,792,707	1,499,417
Noncontrolling Interest in Consolidated Subsidiary:	'	'
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	43,000	43,000
Common Shareholders' Equity:	'	'
Common Stock	0	0
Capital Surplus, Paid In	993,163	992,625
Retained Earnings	1,400,149	1,420,828
Common Shareholders' Equity	2,393,312	2,413,453
Total Capitalization	4,229,019	3,955,870
Total Liabilities and Capitalization	6,850,429	6,911,121
Public Service Company Of New Hampshire [Member]	'	'
Current Assets:	'	'
Cash	2,750	130
Receivables, Net	77,602	76,331
Accounts Receivable from Affiliated Companies	6,271	90
Unbilled Revenues	33,088	38,344
Fuel, Materials and Supplies	141,381	128,736
Regulatory Assets Current	102,473	92,194
Prepayments and Other Current Assets	22,270	24,100
Total Current Assets	385,835	359,925
Property, Plant and Equipment, Net	2,560,635	2,467,556
Deferred Debits and Other Assets:	'	'
Regulatory Assets Long Term	178,204	219,346
Other Long-Term Assets	54,748	39,891
Total Deferred Debits and Other Assets	232,952	259,237
Total Assets	3,179,422	3,086,718
Current Liabilities:	'	'
Notes Payable To Affiliated Companies	153,300	86,500
Long-Term Debt - Current Portion	0	50,000
Accounts Payable - Current	58,801	82,920
Accounts Payable to Affiliated Companies	22,932	22,040
Deferred Tax Liabilities Current	29,936	28,596
Regulatory Liability Current	29,165	20,643
Other Liabilities - Current	38,725	51,729
Total Current Liabilities	332,859	342,428
Deferred Credits and Other Liabilities:	'	'
Accumulated Deferred Income Taxes	566,298	500,166
Regulatory Liabilities Long-Term	50,614	51,723
Other Postretirement Benefit Plan Liability	14,320	15,272
Other Long-Term Liabilities	46,874	46,247
Total Deferred Credits and Other Liabilities	678,106	613,408
Capitalization:	'	'
Long-Term Debt	999,230	999,006
Common Shareholders' Equity:	'	'
Common Stock	0	0
Capital Surplus, Paid In	702,923	701,911
Retained Earnings	473,969	438,515
Accumulated Other Comprehensive Loss	-7,665	-8,550
Common Shareholders' Equity	1,169,227	1,131,876
Total Capitalization	2,168,457	2,130,882
Total Liabilities and Capitalization	3,179,422	3,086,718
Western Massachusetts Electric Company [Member]	'	'
Current Assets:	'	'
Cash	1,737	0
Receivables, Net	50,835	49,018
Accounts Receivable from Affiliated Companies	14,522	47,607
Unbilled Revenues	12,664	16,562
Taxes Receivable	11,504	432
Regulatory Assets Current	38,907	43,024
Marketable Securities - Current	22,107	26,628
Prepayments and Other Current Assets	6,688	10,479
Total Current Assets	158,964	193,750
Property, Plant and Equipment, Net	1,432,368	1,381,060
Deferred Debits and Other Assets:	'	'
Regulatory Assets Long Term	109,690	146,088
Marketable Securities	35,963	31,243
Other Long-Term Assets	50,902	40,679
Total Deferred Debits and Other Assets	196,555	218,010
Total Assets	1,787,887	1,792,820
Current Liabilities:	'	'
Notes Payable To Affiliated Companies	13,200	0
Long-Term Debt - Current Portion	50,000	'
Accounts Payable - Current	36,558	62,961
Accounts Payable to Affiliated Companies	13,312	9,230
Accrued Interest	2,839	7,525
Deferred Tax Liabilities Current	1,920	13,098
Regulatory Liability Current	43,462	19,858
Counterparty Deposit	626	7,688
Other Liabilities - Current	11,758	20,629
Total Current Liabilities	173,675	140,989
Deferred Credits and Other Liabilities:	'	'
Accumulated Deferred Income Taxes	413,701	396,933
Regulatory Liabilities Long-Term	10,289	13,873
Other Postretirement Benefit Plan Liability	2,623	3,911
Other Long-Term Liabilities	38,372	28,619
Total Deferred Credits and Other Liabilities	464,985	443,336
Capitalization:	'	'
Long-Term Debt	578,686	629,389
Common Shareholders' Equity:	'	'
Common Stock	10,866	10,866
Capital Surplus, Paid In	391,136	390,743
Retained Earnings	171,800	181,014
Accumulated Other Comprehensive Loss	-3,261	-3,517
Common Shareholders' Equity	570,541	579,106
Total Capitalization	1,149,227	1,208,495
Total Liabilities and Capitalization	$1,787,887	$1,792,820

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating Revenues	$1,892,532	$1,892,590	$5,860,736	$5,523,475
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	716,631	645,881	2,318,993	1,881,992
Operations and Maintenance	344,092	386,700	1,069,015	1,089,960
Depreciation	153,210	149,105	456,224	463,635
Amortization of Regulatory Assets/(Liabilities), Net	-22,531	70,046	31,826	178,668
Amortization of Rate Reduction Bonds	0	0	0	42,581
Energy Efficiency Programs	118,693	106,097	360,228	306,010
Taxes Other Than Income Taxes	141,527	135,499	421,862	391,846
Total Operating Expenses	1,451,622	1,493,328	4,658,148	4,354,692
Operating Income	440,910	399,262	1,202,588	1,168,783
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	85,208	84,911	260,076	256,205
Other Interest	4,530	2,565	12,132	-5,622
Total Interest Expense	89,738	87,476	272,208	250,583
Other Income/(Loss), Net	11,860	8,945	19,054	21,655
Income Before Income Tax Expense	363,032	320,731	949,434	939,855
Income Tax Expense	126,539	109,351	345,858	325,442
Net Income	236,493	211,380	603,576	614,413
Net Income Attributable to Noncontrolling Interests	1,879	1,879	5,639	5,803
Net Income Attributable to Controlling Interests	234,614	209,501	597,937	608,610
Earnings Per Share Basic And Diluted	$0.74	$0.66	$1.89	$1.93
Common Stock Dividends Per Share Declared	$0.39	$0.37	$1.18	$1.10
Weighted Average Common Shares Outstanding:	'	'	'	'
Basic	316,340,691	315,291,346	315,941,904	315,191,752
Diluted	317,554,925	316,218,239	317,186,490	316,061,131
The Connecticut Light And Power Company [Member]	'	'	'	'
Operating Revenues	695,642	648,420	2,017,580	1,841,846
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	255,787	253,152	736,952	667,266
Operations and Maintenance	127,285	127,104	368,562	359,759
Depreciation	46,886	44,786	139,598	132,356
Amortization of Regulatory Assets/(Liabilities), Net	13,098	-27	62,644	11,223
Energy Efficiency Programs	41,399	24,544	119,389	68,211
Taxes Other Than Income Taxes	64,994	64,979	194,105	182,676
Total Operating Expenses	549,449	514,538	1,621,250	1,421,491
Operating Income	146,193	133,882	396,330	420,355
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	34,743	32,845	102,290	98,163
Other Interest	3,992	2,439	8,158	801
Total Interest Expense	38,735	35,284	110,448	98,964
Other Income/(Loss), Net	6,456	3,861	10,658	10,946
Income Before Income Tax Expense	113,914	102,459	296,540	332,337
Income Tax Expense	30,038	36,136	95,980	113,149
Net Income	83,876	66,323	200,560	219,188
NSTAR Electric Company [Member]	'	'	'	'
Operating Revenues	727,909	753,879	1,955,609	1,916,557
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	317,784	255,244	879,773	659,140
Operations and Maintenance	79,705	97,069	244,610	277,261
Depreciation	47,455	45,441	140,996	136,323
Amortization of Regulatory Assets/(Liabilities), Net	-15,063	72,740	-916	173,289
Amortization of Rate Reduction Bonds	0	0	0	15,054
Energy Efficiency Programs	56,915	58,798	145,499	161,180
Taxes Other Than Income Taxes	34,513	32,610	99,121	95,275
Total Operating Expenses	521,309	561,902	1,509,083	1,517,522
Operating Income	206,600	191,977	446,526	399,035
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	17,996	19,860	58,485	59,261
Other Interest	-658	-1,324	606	-7,612
Total Interest Expense	17,338	18,536	59,091	51,649
Other Income/(Loss), Net	3,287	2,126	3,011	3,275
Income Before Income Tax Expense	192,549	175,567	390,446	350,661
Income Tax Expense	76,975	68,558	156,655	137,499
Net Income	115,574	107,009	233,791	213,162
Public Service Company Of New Hampshire [Member]	'	'	'	'
Operating Revenues	223,664	218,608	735,123	708,550
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	64,397	46,668	247,992	197,765
Operations and Maintenance	65,563	69,477	198,025	191,606
Depreciation	24,568	22,919	73,247	68,433
Amortization of Regulatory Assets/(Liabilities), Net	-9,734	225	-17,565	-1,745
Amortization of Rate Reduction Bonds	0	0	0	19,748
Energy Efficiency Programs	3,766	3,990	10,897	11,036
Taxes Other Than Income Taxes	18,702	18,706	53,051	52,640
Total Operating Expenses	167,262	161,985	565,647	539,483
Operating Income	56,402	56,623	169,476	169,067
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	10,896	10,345	33,812	32,951
Other Interest	128	521	183	1,230
Total Interest Expense	11,024	10,866	33,995	34,181
Other Income/(Loss), Net	461	792	1,673	2,454
Income Before Income Tax Expense	45,839	46,549	137,154	137,340
Income Tax Expense	17,603	18,196	52,199	52,797
Net Income	28,236	28,353	84,955	84,543
Western Massachusetts Electric Company [Member]	'	'	'	'
Operating Revenues	118,145	121,795	363,843	361,763
Operating Expenses:	'	'	'	'
Purchased Power and Transmission	43,926	38,797	130,977	111,095
Operations and Maintenance	20,820	26,148	67,085	70,213
Depreciation	10,506	9,426	31,144	27,707
Amortization of Regulatory Assets/(Liabilities), Net	-8,519	-1,412	-7,778	-598
Amortization of Rate Reduction Bonds	0	0	0	7,780
Energy Efficiency Programs	10,983	12,222	33,096	28,462
Taxes Other Than Income Taxes	9,200	7,696	25,679	20,188
Total Operating Expenses	86,916	92,877	280,203	264,847
Operating Income	31,229	28,918	83,640	96,916
Interest Expense:	'	'	'	'
Interest on Long-Term Debt	6,029	5,814	18,195	17,846
Other Interest	547	417	734	954
Total Interest Expense	6,576	6,231	18,929	18,800
Other Income/(Loss), Net	502	926	1,670	2,349
Income Before Income Tax Expense	25,155	23,613	66,381	80,465
Income Tax Expense	10,490	8,588	26,596	30,424
Net Income	$14,665	$15,025	$39,785	$50,041

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income	$236,493	$211,380	$603,576	$614,413
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	509	509	1,528	1,539
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-216	-38	242	-810
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	1,042	1,611	4,089	4,738
Other Comprehensive Income (Loss), Net of Tax, Total	1,335	2,082	5,859	5,467
Comprehensive Income Attributable to Noncontrolling Interests	-1,879	-1,879	-5,639	-5,803
Comprehensive Income	235,949	211,583	603,796	614,077
The Connecticut Light And Power Company [Member]	'	'	'	'
Net Income	83,876	66,323	200,560	219,188
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	111	111	333	333
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-7	-1	8	-27
Other Comprehensive Income (Loss), Net of Tax, Total	104	110	341	306
Comprehensive Income	83,980	66,433	200,901	219,494
NSTAR Electric Company [Member]	'	'	'	'
Net Income	115,574	107,009	233,791	213,162
Public Service Company Of New Hampshire [Member]	'	'	'	'
Net Income	28,236	28,353	84,955	84,543
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	290	290	871	872
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-13	-2	14	-47
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	277	288	885	822
Comprehensive Income	28,513	28,641	85,840	85,365
Western Massachusetts Electric Company [Member]	'	'	'	'
Net Income	14,665	15,025	39,785	50,041
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease Abstract	'	'	'	'
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	85	85	254	254
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-2	0	2	-8
Other Comprehensive Income (Loss), Net of Tax, Total	83	85	256	246
Comprehensive Income	$14,748	$15,110	$40,041	$50,287

CONSOLIDATED_STATEMENT_OF_CASH

CONSOLIDATED STATEMENT OF CASH FLOWS (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Operating Activities:	'	'
Net Income	$603,576	$614,413
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	456,224	463,635
Deferred Income Tax Expense (Benefit)	64,755	334,225
Pension, SERP and PBOP Expense	74,296	146,803
Pension and PBOP Contributions	-74,681	-338,301
Regulatory Over/(Under) Recoveries, Net	290,111	66,239
Amortization of Regulatory Assets/(Liabilities), Net	31,826	178,668
Amortization of Rate Reduction Bonds	0	42,581
Proceeds from DOE Damages Claim, Net	132,138	'
Other Noncash Income (Expense)	-17,096	3,158
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-66,463	-98,432
Increase Decrease in Fuel, Materials and Supplies	-27,147	-13,134
Taxes Receivable/(Accrued)	26,533	-28,609
Accounts Payable	-69,448	-112,512
Other Current Assets and Liabilities	-20,607	-81,766
Net Cash Flows Provided by Operating Activities	1,404,017	1,176,968
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-1,117,493	-1,073,759
Proceeds from Sales of Marketable Securities	388,352	487,729
Purchases of Marketable Securities	-389,406	-541,070
Decrease In Restricted Cash	0	69,259
Other Investing Activities	-4,669	-1,137
Net Cash Flows Used in Investing Activities	-1,123,216	-1,058,978
Financing Activities:	'	'
Cash Dividends on Common Stock	-356,080	-341,720
Cash Dividends on Preferred Stock	-5,639	-5,802
Increase/(Decrease) in Short-Term Debt	6,000	-172,000
Issuance of Long-Term Debt	650,000	1,350,000
Retirements of Long-Term Debt	-576,650	-840,600
Retirements of Rate Reduction Bonds	0	-82,139
Other Financing Activities	-90	-13,536
Net Cash Flows Provided by/(Used in) Financing Activities	-282,459	-105,797
Net Increase/(Decrease) in Cash	-1,658	12,193
Cash - Beginning of Year	43,364	45,748
Cash - End of Year	41,706	57,941
The Connecticut Light And Power Company [Member]	'	'
Operating Activities:	'	'
Net Income	200,560	219,188
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	139,598	132,356
Deferred Income Tax Expense (Benefit)	-14,400	89,084
Pension, SERP and PBOP Expense, Net of Contributions	8,050	16,182
Regulatory Over/(Under) Recoveries, Net	62,929	24,061
Amortization of Regulatory Assets/(Liabilities), Net	62,644	11,223
Proceeds from DOE Damages Claim	68,610	0
Other Noncash Income (Expense)	-11,290	-8,759
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-87,922	-44,523
Taxes Receivable/(Accrued)	39,805	841
Accounts Payable	16,984	-101,949
Other Current Assets and Liabilities	-2,575	-29,106
Net Cash Flows Provided by Operating Activities	482,993	308,598
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-371,660	-294,638
Other Investing Activities	-4,539	2,013
Net Cash Flows Used in Investing Activities	-376,199	-292,625
Financing Activities:	'	'
Cash Dividends on Common Stock	-128,400	-114,000
Cash Dividends on Preferred Stock	-4,169	-4,169
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	-181,900	-62,200
Retirements of Long-Term Debt	-150,000	-125,000
Capital Contributions from NU Parent	120,000	'
Other Financing Activities	-3,268	-6,352
Net Cash Flows Provided by/(Used in) Financing Activities	-97,737	-721
Net Increase/(Decrease) in Cash	9,057	15,252
Cash - Beginning of Year	7,237	1
Cash - End of Year	16,294	15,253
NSTAR Electric Company [Member]	'	'
Operating Activities:	'	'
Net Income	233,791	213,162
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Bad Debt Expense	15,250	19,012
Depreciation	140,996	136,323
Deferred Income Tax Expense (Benefit)	-39,399	26,358
Pension, SERP and PBOP Expense, Net of Contributions	-11,046	-55,195
Regulatory Over/(Under) Recoveries, Net	155,357	-11,299
Amortization of Regulatory Assets/(Liabilities), Net	-916	173,289
Amortization of Rate Reduction Bonds	0	15,054
Proceeds from DOE Damages Claim	30,193	'
Other Noncash Income (Expense)	-56,851	-48,291
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-47,770	-80,575
Increase Decrease in Fuel, Materials and Supplies	-20,837	7,961
Taxes Receivable/(Accrued)	60,252	-6,345
Accounts Payable	-40,594	6,856
Other Current Assets and Liabilities	32,340	-19,547
Accounts Payable Related Parties	66,758	-59,173
Net Cash Flows Provided by Operating Activities	517,524	317,590
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-309,248	-330,635
Decrease In Restricted Cash	0	37,899
Other Investing Activities	0	575
Net Cash Flows Used in Investing Activities	-309,248	-292,161
Financing Activities:	'	'
Cash Dividends on Common Stock	-253,000	-56,000
Cash Dividends on Preferred Stock	-1,470	-1,633
Increase/(Decrease) in Short-Term Debt	56,000	-120,000
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	-878
Net Cash Flows Provided by/(Used in) Financing Activities	-205,257	-23,654
Net Increase/(Decrease) in Cash	3,019	1,775
Cash - Beginning of Year	8,021	13,695
Cash - End of Year	11,040	15,470
Public Service Company Of New Hampshire [Member]	'	'
Operating Activities:	'	'
Net Income	84,955	84,543
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	73,247	68,433
Deferred Income Tax Expense (Benefit)	67,827	57,066
Pension, SERP and PBOP Expense	4,541	20,427
Pension and PBOP Contributions	-1,637	-112,964
Regulatory Over/(Under) Recoveries, Net	16,813	-1,346
Amortization of Regulatory Assets/(Liabilities), Net	-17,565	-1,745
Amortization of Rate Reduction Bonds	0	19,748
Proceeds from DOE Damages Claim	14,453	'
Other Noncash Income (Expense)	7,930	7,165
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	-7,467	8,047
Increase Decrease in Fuel, Materials and Supplies	-17,350	-30,456
Taxes Receivable/(Accrued)	-24,108	5,103
Accounts Payable	-9,297	29,148
Other Current Assets and Liabilities	13,470	7,220
Net Cash Flows Provided by Operating Activities	205,812	160,389
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-170,127	-155,676
Decrease In Restricted Cash	-45	22,039
Other Investing Activities	-103	-53
Net Cash Flows Used in Investing Activities	-170,275	-133,690
Financing Activities:	'	'
Cash Dividends on Common Stock	-49,500	-51,000
Increase/(Decrease) in Notes Payable to Affiliate	66,800	165,200
Retirements of Long-Term Debt	-50,000	-108,950
Retirements of Rate Reduction Bonds	0	-29,294
Other Financing Activities	-217	456
Net Cash Flows Provided by/(Used in) Financing Activities	-32,917	-23,588
Net Increase/(Decrease) in Cash	2,620	3,111
Cash - Beginning of Year	130	2,493
Cash - End of Year	2,750	5,604
Western Massachusetts Electric Company [Member]	'	'
Operating Activities:	'	'
Net Income	39,785	50,041
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:	'	'
Depreciation	31,144	27,707
Deferred Income Tax Expense (Benefit)	13,479	79,401
Regulatory Over/(Under) Recoveries, Net	33,630	11,685
Amortization of Regulatory Assets/(Liabilities), Net	-7,778	-598
Amortization of Rate Reduction Bonds	0	7,780
Proceeds from DOE Damages Claim	18,883	'
Other Noncash Income (Expense)	615	-544
Changes in Current Assets and Liabilities:	'	'
Receivables and Unbilled Revenues, Net	36,075	-32,231
Taxes Receivable/(Accrued)	-15,831	16,412
Accounts Payable	-12,847	20,260
Other Current Assets and Liabilities	-16,551	-9,857
Net Cash Flows Provided by Operating Activities	120,604	170,056
Investing Activities:	'	'
Investments in Property, Plant and Equipment	-82,546	-127,352
Proceeds from Sales of Marketable Securities	58,788	53,552
Purchases of Marketable Securities	-59,280	-54,042
Other Investing Activities	0	7,401
Net Cash Flows Used in Investing Activities	-83,038	-120,441
Financing Activities:	'	'
Cash Dividends on Common Stock	-49,000	-30,000
Increase/(Decrease) in Notes Payable to Affiliate	13,200	47,900
Retirements of Long-Term Debt	'	-55,000
Retirements of Rate Reduction Bonds	0	-9,352
Other Financing Activities	-29	-7
Net Cash Flows Provided by/(Used in) Financing Activities	-35,829	-46,459
Net Increase/(Decrease) in Cash	1,737	3,156
Cash - Beginning of Year	0	1
Cash - End of Year	$1,737	$3,157

SUMMARY_OF_SIGNIFICANT_ACCOUNT

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 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 and second quarter 2014 combined Quarterly Reports 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 September 30, 2014 and December 31, 2013, the results of operations and comprehensive income for the three and nine months ended September 30, 2014 and 2013, and the cash flows for the nine months ended September 30, 2014 and 2013. The results of operations and comprehensive income for the three and nine months ended September 30, 2014 and 2013, and the cash flows for the nine months ended September 30, 2014 and 2013 are not necessarily indicative of the results expected for a full year.
	NU consolidates CYAPC and YAEC because 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 September 30, 2014			As of December 31, 2013
	NU			$	181.4		$	171.3
	CL&P				85.8			82
	NSTAR Electric				42.3			41.7
	PSNH				7.9			7.4
	WMECO				11.1			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, and is also used to estimate the fair value of preferred stock and long-term debt.
	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 10, "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.
	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 Nine Months Ended
	(Millions of Dollars)	30-Sep-14			30-Sep-13			30-Sep-14		30-Sep-13
	NU	$	35		$	37.5		$	114.6	$	108.9
	CL&P		32.5			35.5			99		97.3
	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 September 30, 2014			As of September 30, 2013
	NU				$	128.9		$	122.9
	CL&P					52.2			36.6
	NSTAR Electric					18.1			31.9
	PSNH					21			16.9
	WMECO					10			13.8
	In the first nine months of 2014, as a result of damages awarded to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 9C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," NU received total proceeds of $132.1 million, which were net of $80.6 million in proceeds CYAPC and YAEC returned to non-affiliated member companies.
	H.       Severance Benefits
	NU recorded severance benefit expenses of $0.7 million and $6.5 million associated with the partial outsourcing of information technology functions and ongoing post-merger integration for the three and nine months ended September 30, 2014, respectively, and $9.2 million for the three and nine months ended September 30, 2013. As of September 30, 2014 and December 31, 2013, the severance accrual totaled $6.4 million and $14.7 million, respectively, and was included in Other Current Liabilities on the balance sheets.

REGULATORY_ACCOUNTING

REGULATORY ACCOUNTING	9 Months Ended
	Sep. 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 September 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Benefit Costs	$	1,113.20		$	1,240.20
	Derivative Liabilities		427.5			638
	Income Taxes, Net		623.2			626.2
	Storm Restoration Costs		493.5			589.6
	Goodwill-related		510.5			525.9
	Regulatory Tracker Mechanisms		235.7			323.4
	Contractual Obligations - Yankee Companies		124.6			154.2
	Buy Out Agreements for Power Contracts		49.8			70.2
	Other Regulatory Assets		109.1			126.8
	Total Regulatory Assets		3,687.10			4,294.50
	Less: Current Portion		446			535.8
	Total Long-Term Regulatory Assets	$	3,241.10		$	3,758.70
			As of September 30, 2014									As of December 31, 2013
						NSTAR								NSTAR
	(Millions of Dollars)		CL&P			Electric		PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Benefit Costs		$	242.2		$	318.1	$	78.1	$	44.3	$	297.7	$	496.7	$	100.6	$	57.3
	Derivative Liabilities			421.1			4.3		-		-		630.4		7.7		-		-
	Income Taxes, Net			427.4			83.3		38.3		35.3		415.5		84		40.3		43.7
	Storm Restoration Costs			326			106.2		29.3		32		397.8		109.3		43.7		38.8
	Goodwill-related			-			438.3		-		-		-		451.5		-		-
	Regulatory Tracker Mechanisms			5.2			76.4		94.7		23.5		8		169.5		83.3		32.6
	Buy Out Agreements for Power Contracts			-			45.4		4.4		-		-		64.7		5.5		-
	Other Regulatory Assets			63.6			54.2		35.9		13.5		64.6		55.9		38.1		16.7
	Total Regulatory Assets			1,485.50			1,126.20		280.7		148.6		1,814.00		1,439.30		311.5		189.1
	Less: Current Portion			116.5			128.2		102.5		38.9		150.9		204.1		92.2		43
	Total Long-Term Regulatory Assets		$	1,369.00		$	998	$	178.2	$	109.7	$	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 (with carrying charges) associated with five major storms that occurred in 2011 and 2012. CL&P will recover these costs in its distribution rates over a six-year period beginning December 1, 2014. Effective June 1, 2014, CL&P received $65.4 million of DOE Phase II Damages proceeds. On June 17, 2014, the PURA ordered CL&P to refund these proceeds to customers by offsetting the deferred storm restoration costs regulatory asset. For further information on the DOE Phase II Damages proceeds received from the Yankee Companies, see Note 9C, "Commitments and Contingencies - Contractual Obligations - Yankee Companies," to the financial statements.
	Regulatory Costs in Other Long-Term Assets: The Regulated companies had $64.7 million ($3.2 million for CL&P, $36 million for NSTAR Electric, and $11.2 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 September 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 September 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Cost of Removal	$	439.1		$	435.1
	Regulatory Tracker Mechanisms		339.9			151.2
	AFUDC - Transmission		67.2			68.1
	Other Regulatory Liabilities		62.7			52.9
	Total Regulatory Liabilities		908.9			707.3
	Less: Current Portion		399			204.3
	Total Long-Term Regulatory Liabilities	$	509.9		$	503
			As of September 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		$	22.5		$	260.7	$	49.2	$	-	$	29.1	$	250	$	49.7	$	-
	Regulatory Tracker Mechanisms			196.4			67.3		25.9		43.9		95.6		21.9		21.6		21.1
	AFUDC - Transmission			53.9			4.1		-		9.2		54.7		4.1		-		9.3
	Other Regulatory Liabilities			10.6			31.6		4.7		0.7		8.4		31.1		1		3.4
	Total Regulatory Liabilities			283.4			363.7		79.8		53.8		187.8		307.1		72.3		33.8
	Less: Current Portion			195.7			97.2		29.2		43.5		94		54		20.6		19.9
	Total Long-Term Regulatory Liabilities		$	87.7		$	266.5	$	50.6	$	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 9E, "Commitments and Contingencies – FERC Base ROE Complaints," in the second quarter of 2014 the Company had recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact of these rulings. As of September 30, 2014, the cumulative pre-tax reserves (excluding interest) totaled $76.1 million at NU, $42.9 million at CL&P, $15.6 million at NSTAR Electric, $5.9 million at PSNH and $11.7 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 (excluding interest) of $23.7 million at NU, $12.8 million at CL&P, $5.7 million at NSTAR Electric, $2.3 million at PSNH and $2.9 million at WMECO. These reserves were recorded in each electric subsidiary's respective transmission regulatory tracker mechanism and as a reduction of Operating Revenues.
	Effective June 1, 2014, as a result of damages awarded to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 9C, "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. 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. Refunds to customers for these DOE proceeds began in the third quarter of 2014.

PROPERTY_PLANT_AND_ACCUMULATED

PROPERTY, PLANT AND ACCUMULATED DEPRECIATION	9 Months Ended
	Sep. 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 September 30, 2014			As of December 31, 2013
	(Millions of Dollars)			NU			NU
	Distribution - Electric			$	12,306.60		$	11,950.20
	Distribution - Natural Gas				2,494.50			2,425.90
	Transmission				6,564.20			6,412.50
	Generation				1,168.60			1,152.30
	Electric and Natural Gas Utility				22,533.90			21,940.90
	Other (1)				541.7			508.7
	Property, Plant and Equipment, Gross				23,075.60			22,449.60
	Less: Accumulated Depreciation
		Electric and Natural Gas Utility			-5,687.00			-5,387.00
		Other			-216.3			-196.2
	Total Accumulated Depreciation				-5,903.30			-5,583.20
	Property, Plant and Equipment, Net				17,172.30			16,866.40
	Construction Work in Progress				1,082.30			709.8
	Total Property, Plant and Equipment, Net			$	18,254.60		$	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 September 30, 2014										As of December 31, 2013
					NSTAR									NSTAR
	(Millions of Dollars)	CL&P			Electric			PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Distribution	$	5,104.80		$	4,812.40		$	1,654.50	$	774.8	$	4,930.70	$	4,694.70	$	1,608.20	$	756.6
	Transmission		3,125.20			1,824.60			715.8		851.8		3,071.90		1,772.30		695.7		826.4
	Generation		-			-			1,134.70		33.9		-		-		1,131.20		21.1
	Property, Plant and Equipment, Gross		8,230.00			6,637.00			3,505.00		1,660.50		8,002.60		6,467.00		3,435.10		1,604.10
	Less: Accumulated Depreciation		-1,908.20			-1,726.70			-1,069.40		-291.8		-1,804.10		-1,631.30		-1,021.80		-271.5
	Property, Plant and Equipment, Net		6,321.80			4,910.30			2,435.60		1,368.70		6,198.50		4,835.70		2,413.30		1,332.60
	Construction Work in Progress		379			301.4			125		63.7		252.8		208.2		54.3		48.5
	Total Property, Plant and Equipment, Net	$	6,700.80		$	5,211.70		$	2,560.60	$	1,432.40	$	6,451.30	$	5,043.90	$	2,467.60	$	1,381.10

DERIVATIVE_INSTRUMENTS

DERIVATIVE INSTRUMENTS	9 Months Ended
	Sep. 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, which are subject to price volatility, for their customers. 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. 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 September 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		$	-		$	0.4
	Level 3:
		NU (1)		17.4			-6.8			10.6
		CL&P (1)		16.4			-6.8			9.6
		NSTAR Electric		1			-			1
	Long-Term Derivative Assets:
	Level 3:
		NU (1)	$	96		$	-20.9		$	75.1
		CL&P (1)		95.1			-20.9			74.2
		NSTAR Electric		0.9			-			0.9
	Current Derivative Liabilities:
	Level 2:
		NU (1)	$	-2.4		$	0.4		$	-2
	Level 3:
		NU		-88.3			-			-88.3
		CL&P		-86.8			-			-86.8
		NSTAR Electric		-1.5			-			-1.5
	Long-Term Derivative Liabilities:
	Level 3:
		NU	$	-420.9		$	-		$	-420.9
		CL&P		-418.1			-			-418.1
		NSTAR Electric		-2.8			-			-2.8
			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 At Fair Value with Offsetting Regulatory Amounts
	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 September 30, 2014 and December 31, 2013, NU had NYMEX future contracts in order to reduce variability associated with the purchase price of approximately 9.7 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 September 30,							For the Nine Months Ended September 30,
(Millions of Dollars)			2014			2013				2014			2013
NU
Balance Sheets:
	Regulatory Assets and Liabilities		$	-15.7		$	0.3			$	149.9		$	48.8
Statements of Income:
	Purchased Power, Fuel and Transmission			-			0.2				-			0.9
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 September 30, 2014									As of December 31, 2013
		Range						Period Covered			Range					Period Covered
Energy Prices:
NU	$	66	-	68	per MWh			2018 - 2020		$	49	-	77	per MWh		2018 - 2029
CL&P	$	66	-	68	per MWh			2018 - 2020		$	56	-	58	per MWh		2018 - 2029
Capacity Prices:
NU	$	7.03	-	12.98		per kW-Month		2016 - 2026		$	5.07	-	11.82		per kW-Month	2017 - 2029
CL&P	$	7.03	-	12.98		per kW-Month		2018 - 2026		$	5.07	-	10.42		per kW-Month	2017 - 2026
NSTAR Electric	$	11	-	11.1		per kW-Month		2016 - 2019		$	5.07	-	7.38		per kW-Month	2017 - 2019
Forward Reserve:
NU, CL&P	$	5.8	-	9.5		per kW-Month		2014 - 2024		$	3.3	-	3.3		per kW-Month	2014 - 2024
REC Prices:
NU	$	41	-	70	per REC			2014 - 2018		$	36	-	87	per REC		2014 - 2029
NSTAR Electric	$	41	-	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 September 30,						For the Nine Months Ended September 30,
		2014			2013			2014			2013
(Millions of Dollars)		NU			NU			NU			NU
Derivatives, Net:
Fair Value as of Beginning of Period		$	-430.9		$	-788.1		$	-635.2		$	-878.6
Net Realized/Unrealized Gains Included in:
	Net Income		-			1.2			-			8.3
	Regulatory Assets and Liabilities		-13.6			0.8			147.6			49.6
Settlements			21			21.3			64.1			55.9
Fair Value as of End of Period		$	-423.5		$	-764.8		$	-423.5		$	-764.8
		For the Three Months Ended September 30,
		2014							2013
(Millions of Dollars)		CL&P			NSTAR Electric				CL&P			NSTAR Electric
Derivatives, Net:
Fair Value as of Beginning of Period		$	-424.6		$	-6.3			$	-775.8		$	-13.1
Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities			-15			1.4				-1.2			0.5
Settlements			18.5			2.5				21.7			1
Fair Value as of End of Period		$	-421.1		$	-2.4			$	-755.3		$	-11.6
		For the Nine Months Ended September 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			149.4			0.9				45.1			0.6
Settlements			60.1			4				65.8			2.7
Fair Value as of End of Period		$	-421.1		$	-2.4			$	-755.3		$	-11.6

MARKETABLE_SECURITIES

MARKETABLE SECURITIES	9 Months Ended
	Sep. 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 September 30, 2014, the mutual funds and equity investments were classified as Level 1 in the fair value hierarchy and totaled $58.2 million and $24.4 million, respectively. As of December 31, 2013, the mutual funds were classified as Level 1 and totaled $57.2 million. For the three months ended September 30, 2014 and 2013, net losses of $1.9 million and net gains of $3 million, respectively, were recorded in Other Income, Net. For the nine months ended September 30, 2014 and 2013, net gains of $1.9 million and $7.3 million, respectively, were recorded in Other Income, Net. 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 September 30, 2014
						Pre-Tax			Pre-Tax
			Amortized			Unrealized			Unrealized
	(Millions of Dollars)		Cost			Gains			Losses			Fair Value
	NU
		Debt Securities (1)	$	310.6		$	7.8		$	-0.2		$	318.2
		Equity Securities (1)		160.9			71.1			-			232
	WMECO
		Debt Securities (2)		58.1			0.1			-0.1			58.1
			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 $447.7 million and $424 million as of September 30, 2014 and December 31, 2013, respectively, which are legally restricted and can only be used for the costs of 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 September 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)		$	47.6		$	47.6		$	21.9		$	22.1
	One to five years			91			91.4			30.7			30.5
	Six to ten years			65.6			67.5			1.4			1.4
	Greater than ten years			106.4			111.7			4.1			4.1
	Total Debt Securities		$	310.6		$	318.2		$	58.1		$	58.1
	(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-Sep-14			31-Dec-13			30-Sep-14			31-Dec-13
	Level 1:
		Mutual Funds and Equities			$	314.6		$	281.3		$	-		$	-
		Money Market Funds				27.1			32.9			4.4			10.9
	Total Level 1				$	341.7		$	314.2		$	4.4		$	10.9
	Level 2:
		U.S. Government Issued Debt Securities (Agency and Treasury)			$	56.5		$	61.4		$	-		$	6.8
		Corporate Debt Securities				61.2			53.6			14.1			15.1
		Asset-Backed Debt Securities				37.9			30.4			14.3			9
		Municipal Bonds				112.5			105.5			13.9			11.2
		Other Fixed Income Securities				23			15.8			11.4			4.9
	Total Level 2				$	291.1		$	266.7		$	53.7		$	47
	Total Marketable Securities				$	632.8		$	580.9		$	58.1		$	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	9 Months Ended
	Sep. 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 extended the expiration date of their joint $1.45 billion revolving credit facility for one 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 September 30, 2014 and December 31, 2013, NU had $964.5 million and $1.01 billion, respectively, in short-term borrowings outstanding under the NU parent commercial paper program, leaving $485.5 million and $435.5 million of available borrowing capacity as of September 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of September 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 September 30, 2014, there were intercompany loans from NU of $105.4 million to CL&P, $153.3 million to PSNH and $13.2 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 extended the expiration date of its $450 million revolving credit facility for one additional year to September 6, 2019. This facility serves to backstop NSTAR Electric's existing $450 million commercial paper program. As of September 30, 2014 and December 31, 2013, NSTAR Electric had $159.5 million and $103.5 million, respectively, in short-term borrowings outstanding under its commercial paper program, leaving $290.5 million and $346.5 million of available borrowing capacity as of September 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of September 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.
	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. As the debt issuance refinanced short-term debt, the short-term debt was 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 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 borrowings.
	On September 15, 2014, CL&P repaid at maturity the $150 million of 4.80 percent 2004 Series A First Mortgage Bonds.
	On October 14, 2014, PSNH issued $75 million of first mortgage bonds at a yield of 3.144 percent that will mature on November 1, 2023. The first mortgage bonds are part of the same series of PSNH's existing 3.50 percent Series S First Mortgage Bonds that were initially issued in November 2013. As a result, the aggregate principal amount of PSNH's outstanding Series S First Mortgage Bonds totals $325 million. The proceeds, net of issuance costs, were used to repay short-term borrowings. As the debt issuance refinanced short-term debt, the short-term debt was classified as Long-Term Debt on NU's balance sheet as of September 30, 2014.
	On August 27, 2014, PURA approved CL&P's request to extend the authorization period for issuance of up to $366.4 million in long-term debt from December 31, 2014 to December 31, 2015.

PENSION_BENEFITS_AND_POSTRETIR

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS	9 Months Ended
	Sep. 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 shown 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 Nine Months Ended
		30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	19.1	$	25.6	$	60.7	$	76.7
	Interest Cost		56.4		51.7		169.5		155
	Expected Return on Plan Assets		-77.7		-69.5		-233.1		-208.5
	Actuarial Loss		31.7		52.4		96.5		158.1
	Prior Service Cost		1.1		1.1		3.3		3
	Total Net Periodic Benefit Expense	$	30.6	$	61.3	$	96.9	$	184.3
	Capitalized Pension Expense	$	8.3	$	18.3	$	26.7	$	54.9
		PBOP				PBOP
		For the Three Months Ended				For the Nine Months Ended
		30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	3.1	$	4.2	$	9.3	$	12.6
	Interest Cost		12.4		11.8		37.1		35.4
	Expected Return on Plan Assets		-15.8		-13.9		-47.4		-41.6
	Actuarial Loss		3		6.5		9.1		19.5
	Prior Service Credit		-0.7		-0.5		-2.1		-1.5
	Total Net Periodic Benefit Expense	$	2	$	8.1	$	6	$	24.4
	Capitalized PBOP Expense	$	1.1	$	2.6	$	1.9	$	7.6
		Pension and SERP
		For the Three Months Ended September 30, 2014								For the Three Months Ended September 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	$	8.3		3.3	$	1.2
	Interest Cost		12.5		10.3		5.7		2.5		12.1		14.5		5.8		2.5
	Expected Return on Plan Assets		-18.7		-15.7		-9.3		-4.4		-18.4		-21.1		-9.2		-4.3
	Actuarial Loss		8.2		5.9		2.8		1.7		13.9		14.4		5.4		2.9
	Prior Service Cost		0.4		-		0.1		0.1		0.4		-		0.1		0.1
	Total Net Periodic Benefit Expense	$	7.4	$	3.5	$	1.6	$	0.7	$	14.3	$	16.1	$	5.4	$	2.4
	Intercompany Allocations	$	6.5	$	2.9	$	1.8	$	1.2	$	11.4	$	-2.1	$	2.6	$	2
	Capitalized Pension Expense	$	4.3	$	2.6	$	0.7	$	0.6	$	7	$	9.8	$	1.7	$	1.3
		Pension and SERP
		For the Nine Months Ended September 30, 2014								For the Nine Months Ended September 30, 2013
				NSTAR								NSTAR
	(Millions of Dollars)	CL&P		Electric		PSNH		WMECO		CL&P		Electric(1)		PSNH		WMECO
	Service Cost	$	15.2	$	10.6	$	7.4	$	2.7	$	18.7	$	24.8	$	9.8	$	3.5
	Interest Cost		38.1		31		18		7.8		36.3		43.5		17.8		7.5
	Expected Return on Plan Assets		-56.7		-47.3		-28.8		-13.5		-55.4		-63.3		-26.2		-13
	Actuarial Loss		25.5		17.6		8.9		5.2		42		43.6		16.2		8.9
	Prior Service Cost/(Credit)		1.4		-		0.5		0.3		1.4		-0.2		0.4		0.3
	Total Net Periodic Benefit Expense	$	23.5	$	11.9	$	6	$	2.5	$	43	$	48.4	$	18	$	7.2
	Intercompany Allocations	$	20.8	$	6.7	$	6	$	3.9	$	33.6	$	-6.2	$	7.8	$	6
	Capitalized Pension Expense	$	13.6	$	5.5	$	2.4	$	2	$	21	$	21.6	$	5.6	$	3.9
		PBOP
		For the Three Months Ended September 30, 2014								For the Three Months Ended September 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	0.6	$	0.8	$	0.3	$	0.1	$	0.9	$	0.6	$	0.2
	Interest Cost		2		4.9		1.1		0.4		2		1		0.4
	Expected Return on Plan Assets		-2.6		-6.5		-1.4		-0.6		-2.5		-1.3		-0.6
	Actuarial Loss/(Gain)		1		-0.1		0.6		0.1		1.8		0.9		0.3
	Prior Service Credit		-		-0.5		-		-		-		-		-
	Total Net Periodic Benefit Expense/(Income)	$	1	$	-1.4	$	0.6	$	0	$	2.2	$	1.2	$	0.3
	Intercompany Allocations	$	0.9	$	0.3	$	0.2	$	0.2	$	1.7	$	0.4	$	0.3
	Capitalized PBOP Expense/(Income)	$	0.5	$	-0.5	$	0.2	$	-	$	1.3	$	0.4	$	0.3
		PBOP
		For the Nine Months Ended September 30, 2014								For the Nine Months Ended September 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	1.7	$	2.3	$	1	$	0.3	$	2.6	$	1.7	$	0.5
Interest Cost		6		14.6		3.2		1.3		5.9		3.1		1.3
Expected Return on Plan Assets		-7.9		-19.5		-4.1		-1.7		-7.6		-3.9		-1.7
Actuarial Loss/(Gain)		3.2		-0.4		1.7		0.3		5.6		2.7		0.8
Prior Service Credit		-		-1.4		-		-		-		-		-
Total Net Periodic Benefit Expense/(Income)	$	3	$	-4.4	$	1.8	$	0.2	$	6.5	$	3.6	$	0.9
Intercompany Allocations	$	3.1	$	0.4	$	0.8	$	0.6	$	5.3	$	1.2	$	1
Capitalized PBOP Expense/(Income)	$	1.5	$	-1.5	$	0.6	$	0.1	$	3.7	$	1.1	$	0.7
NSTAR Electric's pension amounts for the three and nine months ended September 30, 2013 do not include SERP expense.
For the three and nine months ended September 30, 2013, the net periodic PBOP expense allocated to NSTAR Electric was $1.2 million and $3.5 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. This change had no impact on the income statement or net assets of NSTAR Electric or NU.
As of September 30, 2014, the liabilities associated with the Pension, SERP and PBOP plans for NSTAR Electric were $83.4 million for the Pension Plan, $3.6 million for the SERP Plans ($0.4 million of which is included in other current liabilities) and $55.6 million for the PBOP Plan. As of December 31, 2013, the liability associated with the NSTAR Pension Plan for NSTAR Electric was $118 million.

INCOME_TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Income Tax Disclosure [Text Block]	'
	8.       INCOME TAXES
	In the third quarter of 2014, the Company recorded a reduction to its state credit carryforwards of $11 million (CL&P $10.1 million), net of tax, as a result of an update to reflect the amounts expired. Further, the Company decreased its valuation allowance reserve for state credits by $22.3 million (all at CL&P), net of tax, to reflect the expiration of state credits in its recently filed return and the latest available data. These updates resulted in a net reduction in income tax expense of $11.3 million (CL&P $12.2 million).

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Commitments and Contingencies Disclosure [Text Block]	'
	9.       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 September 30, 2014							As of December 31, 2013
					Reserve							Reserve
		Number of Sites			(in millions)				Number of Sites			(in millions)
	NU		65		$	34.7				68		$	35.4
	CL&P		16			4				18			3.4
	NSTAR Electric		13			1.1				12			1.2
	PSNH		13			5.3				15			5.4
	WMECO		4			0.5				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 September 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 CL&P, NSTAR Electric and WMECO for the purchase of energy and capacity from renewable energy facilities.
		October - December
	(Millions of Dollars)	2014			2015			2016			2017			2018			Thereafter			Total
	CL&P	$	20		$	60.7		$	66.1		$	67		$	67.7		$	717		$	998.5
	NSTAR Electric		21.8			86.3			100			96.1			59.6			377.6			741.4
	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 September 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. Refunds to customers for these DOE proceeds began in the third quarter of 2014. 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.
	DOE Phase I Damages - Proceeds Received – On September 17, 2014, in accordance with the MYAPC refund plan, MYAPC returned a portion of the DOE Phase I Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, in the amount of $3.2 million, $1.1 million, $1.4 million and $0.8 million, respectively. These amounts reduced receivables at CL&P, NSTAR Electric, PSNH and WMECO.
	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 September 30, 2014:
					Maximum Exposure
	Subsidiary		Description		(in millions)				Expiration Dates
	Various		Surety Bonds		$	64.3			2014 - 2016 (1)
	Various		New England Hydro Companies' Long-Term Debt		$	2			Unspecified
	NUSCO and RRR		Lease Payments for Vehicles and Real Estate		$	15.3			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
	First Complaint: On September 30, 2011, a complaint was filed jointly at FERC under Sections 206 and 306 of the Federal Power Act (the "first complaint") 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 prospectively from the date of a final FERC order (the "FERC order date"), and for the 15-month period October 1, 2011 to December 31, 2012 (the "first complaint refund period"), 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 on the first complaint finding that the base ROE in effect during the first complaint refund period was not reasonable and recommended separate base ROEs for the first complaint refund period of 10.6 percent and for the period beginning when FERC issues its final decision (the "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 first complaint refund period. See Cumulative Reserves below for further information on the reserves recorded in the third quarter of 2013.
	On June 19, 2014, FERC issued an order on the first complaint, partially affirming and partially reversing the FERC ALJ's initial decision. FERC set a single tentative base ROE of 10.57 percent for the first complaint 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 halfway between the midpoint and the top of the zone of reasonableness. 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 (the "paper hearing"). Rehearing requests on this new methodology were filed in July, and briefs were filed in August and September by the parties on the appropriate long-term growth rate. In the second quarter of 2014, the Company recorded additional reserves at its electric subsidiaries to recognize the potential financial impact from the FERC's June 19th order. See Cumulative Reserves below for further information on the reserves recorded in the second quarter of 2014.
	On October 16, 2014, the FERC issued an order in the paper hearing, which confirmed that the base ROE should be set at 10.57 percent and that a utility's total or maximum ROE should not exceed the top of the new zone of reasonableness (11.74 percent). The FERC ordered the NETOs to provide refunds to customers for the first complaint refund period, and set the new base ROE prospectively from the order date.
	Second Complaint: On December 27, 2012, a second complaint was filed jointly at FERC by several additional consumer groups and municipal parties (the "second complaint"), which challenged the NETOs' base ROE prospectively from the FERC order date and sought refunds for the 15-month period January 1, 2013 to March 31, 2014 (the "second complaint refund period").
	On June 19, 2014, FERC issued an order finding that the second complaint raised issues of material fact. On July 21, 2014, the NETOs filed a rehearing request in this proceeding. On October 24, 2014, the FERC assigned the case for trial before a FERC ALJ after settlement negotiations were unsuccessful. The FERC ALJ has set a trial date beginning June 8, 2015, and will issue an initial decision on or before October 26, 2015. In the second quarter of 2014, the Company recorded reserves at its electric subsidiaries to recognize the potential financial impact from the FERC's June 19th order for the second complaint refund period. See Cumulative Reserves below for further information on the reserves recorded in the second quarter of 2014.
	Third Complaint: On July 31, 2014, a third complaint was filed at FERC (the "third complaint") by most of the Complainants to the first and second complaints, claiming that the base ROE and incentive adders exceed the range of permissible ROEs, requesting FERC to reduce the NETO's base ROE prospectively from the FERC order date, and seeking refunds for the 15-month period beginning August 1, 2014 (the "third complaint refund period"). FERC has taken no action on this complaint to date. At this time, the Company cannot determine the outcome of this complaint.
	Cumulative Reserves: The following is a summary as of September 30, 2014 of the cumulative reserves (excluding interest) that the Company established in the third quarter of 2013 and the second quarter of 2014 to recognize the potential financial impacts of the first and second complaints. Management is currently evaluating the impact of the October 16th order on the previously established reserves.
			NU
				Third Quarter			Second Quarter
	(Millions of Dollars)			2013			2014		Total
	1st Complaint - Base ROE		$	23.7		$	1.2		$	24.9
	2nd Complaint - Base ROE			-			27.4			27.4
	Incentive ROE (1st and 2nd Complaint)			-			23.8			23.8
	Cumulative Reserve		$	23.7		$	52.4		$	76.1
			CL&P									NSTAR Electric
				Third Quarter			Second Quarter						Third Quarter			Second Quarter
	(Millions of Dollars)			2013			2014		Total				2013			2014		Total
	1st Complaint - Base ROE		$	12.8		$	0.5		$	13.3		$	5.7		$	0.4		$	6.1
	2nd Complaint - Base ROE			-			13.5			13.5			-			7.5			7.5
	Incentive ROE (1st and 2nd Complaint)			-			16.1			16.1			-			2			2
	Cumulative Reserve		$	12.8		$	30.1		$	42.9		$	5.7		$	9.9		$	15.6
		PSNH									WMECO
			Third Quarter			Second Quarter						Third Quarter			Second Quarter
(Millions of Dollars)			2013			2014		Total				2013			2014		Total
1st Complaint - Base ROE		$	2.3		$	0.1		$	2.4		$	2.9		$	0.2		$	3.1
2nd Complaint - Base ROE			-			2.7			2.7			-			3.7			3.7
Incentive ROE (1st and 2nd Complaint)			-			0.8			0.8			-			4.9			4.9
Cumulative Reserve		$	2.3		$	3.6		$	5.9		$	2.9		$	8.8		$	11.7
The aggregate after-tax charge to second quarter 2014 earnings resulting from the June 19, 2014 FERC orders totaled $32.1 million at NU, $18.5 million at CL&P, $6.1 million at NSTAR Electric, $2 million at PSNH and $5.5 million at WMECO. In the third quarter of 2013, the aggregate after-tax charge to earnings totaled $14.3 million at NU, $7.7 million at CL&P, $3.4 million at NSTAR Electric, $1.4 million at PSNH and $1.8 million at WMECO.
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	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Fair Value Disclosures [Text Block]	'
	10.       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 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. 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 September 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	$	151	$	155.6	$	152.7
	Long-Term Debt		8,412.60		8,876.30		8,310.20		8,443.10
		As of September 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	$	110.1	$	43	$	40.9	$	-	$	-	$	-	$	-
	Long-Term Debt		2,841.80		3,189.50		1,797.40		1,959.40		999.2		1,046.40		628.7		667.4
		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 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.
	See Note 1D, "Summary of Significant Accounting Policies - Fair Value Measurements," for the fair value measurement policy and the fair value hierarchy.

ACCUMULATED_OTHER_COMPREHENSIV

ACCUMULATED OTHER COMPREHENSIVE INCOME	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Comprehensive Income Note [Text Block]	'
	11.       ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)
	The changes in accumulated other comprehensive income/(loss) by component, net of tax, is as follows:
			For the Nine Months Ended September 30, 2014												For the Nine Months Ended September 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			-			0.2			1.2			1.4			-		-0.8		-		-0.8
	Amounts Reclassified from AOCI			1.5			-			2.9			4.4			1.5		-		4.8		6.3
	Net OCI			1.5			0.2			4.1			5.8			1.5		-0.8		4.8		5.5
	AOCI as of End of Period		$	-12.9		$	0.6		$	-27.9		$	-40.2		$	-14.9	$	0.5	$	-53	$	-67.4
	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 Nine Months Ended
		September 30,						September 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		$	-2.5		$	-2.5		Interest Expense
	Tax Benefit		0.3			0.3			1			1		Income Tax Expense
	Qualified Cash Flow Hedging Instruments, Net of Tax	$	-0.5		$	-0.5		$	-1.5		$	-1.5
	Pension, SERP and PBOP Benefit Plan Costs:
	Amortization of Actuarial Losses	$	-1.6		$	-2.5		$	-4.7		$	-7.3		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		-1.6			-2.5			-4.8			-7.4
	Tax Benefit		0.6			0.9			1.9			2.6		Income Tax Expense
	Pension, SERP and PBOP Benefit Plan Costs, Net of Tax	$	-1		$	-1.6		$	-2.9		$	-4.8
	Total Amounts Reclassified from AOCI, Net of Tax	$	-1.5		$	-2.1		$	-4.4		$	-6.3
	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	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Stock by Class [Text Block]	'
	12.       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		September 30, 2014 and	Issued as of
		Par Value		31-Dec-13	30-Sep-14	31-Dec-13
	NU	$	5	380,000,000	333,353,446	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 September 30, 2014 and December 31, 2013, there were 16,730,815 and 17,796,672 NU common shares held as treasury shares, respectively. As of September 30, 2014 and December 31, 2013, NU common shares outstanding were 316,622,631 and 315,273,559, respectively.

COMMON_SHARESHOLDERS_EQUITY_AN

COMMON SHARESHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (NU)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Stockholders' Equity Note Disclosure [Text Block]	'
	13	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-Sep-14				30-Sep-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		$	9,753.80	$	155.6	$	9,406.60	$	155.6
	Net Income			236.5		-		211.4		-
	Dividends on Common Shares			-124.2		-		-114.9		-
	Dividends on Preferred Stock			-1.9		-1.9		-1.9		-1.9
	Issuance of Common Shares			1		-		1.4		-
	Other Transactions, Net			24.1		-		12.8		-
	Net Income Attributable to Noncontrolling Interests			-		1.9		-		1.9
	Other Comprehensive Income			1.3		-		2.1		-
	Balance as of End of Period		$	9,890.60	$	155.6	$	9,517.50	$	155.6
			For the Nine Months Ended
			30-Sep-14				30-Sep-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			603.6		-		614.4		-
	Dividends on Common Shares			-372.2		-		-346.9		-
	Dividends on Preferred Stock			-5.6		-5.6		-5.8		-5.8
	Issuance of Common Shares			6.4		-		10.2		-
	Other Transactions, Net			41		-		3		-
	Net Income Attributable to Noncontrolling Interests			-		5.6		-		5.8
	Other Comprehensive Income			5.9		-		5.5		-
	Balance as of End of Period		$	9,890.60	$	155.6	$	9,517.50	$	155.6

EARNINGS_PER_SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Earnings Per Share [Text Block]	'
	14.       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 nine months ended September 30, 2014 or for the three months ended September 30, 2013. For the nine months ended September 30, 2013, there were 2,100 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 Nine Months Ended
	(Millions of Dollars, except share information)		30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	Net Income Attributable to Controlling Interest		$	234.6	$	209.5	$	597.9	$	608.6
	Weighted Average Common Shares Outstanding:
		Basic		316,340,691		315,291,346		315,941,904		315,191,752
		Dilutive Effect		1,214,234		926,893		1,244,586		869,379
		Diluted		317,554,925		316,218,239		317,186,490		316,061,131
	Basic and Diluted EPS		$	0.74	$	0.66	$	1.89	$	1.93
	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	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	15.       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 nine months ended September 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 unregulated 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 September 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,502.60	$	109.2	$	262.5	$	211.2	$	-193	$	1,892.50
	Depreciation and Amortization		-71.7		-16.4		-37.4		-13.8		8.6		-130.7
	Other Operating Expenses		-1,141.50		-98.4		-74.2		-192.4		185.6		-1,320.90
	Operating Income/(Loss)		289.4		-5.6		150.9		5		1.2		440.9
	Interest Expense		-49.2		-8.5		-24.5		-8.6		1		-89.8
	Other Income, Net		9.3		0.1		2.7		226.4		-226.6		11.9
	Net Income Attributable to Controlling Interest	$	153.4	$	-9.9	$	88.1	$	228.3	$	-225.3	$	234.6
		For the Nine Months Ended September 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	4,350.40	$	737.5	$	721.4	$	568.1	$	-516.7	$	5,860.70
	Depreciation and Amortization		-309.9		-51.1		-111.4		-28.3		12.7		-488
	Other Operating Expenses		-3,343.90		-586.2		-211.5		-534.1		505.6		-4,170.10
	Operating Income		696.6		100.2		398.5		5.7		1.6		1,202.60
	Interest Expense		-143.8		-25.6		-78.8		-27.2		3.2		-272.2
	Other Income, Net		13.6		0.2		6.9		657.9		-659.5		19.1
	Net Income Attributable to Controlling Interest	$	349.1	$	44.2	$	206.8	$	653.4	$	-655.6	$	597.9
	Cash Flows Used for Investments in Plant	$	480.1	$	120.6	$	469.9	$	46.9	$	-	$	1,117.50
		For the Three Months Ended September 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,508.60	$	97.1	$	234.1	$	212.5	$	-159.7	$	1,892.60
	Depreciation and Amortization		-159.6		-16.4		-34.5		-11.2		2.6		-219.1
	Other Operating Expenses		-1,064.10		-89.4		-73.4		-206.8		159.5		-1,274.20
	Operating Income/(Loss)		284.9		-8.7		126.2		-5.5		2.4		399.3
	Interest Expense		-44.3		-8.6		-26.6		-9.2		1.2		-87.5
	Other Income, Net		5.5		0.5		2.9		312.1		-312.1		8.9
	Net Income/(Loss) Attributable to Controlling Interest	$	156.9	$	-10.4	$	58.6	$	313.1	$	-308.7	$	209.5
		For the Nine Months Ended September 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	4,104.40	$	613	$	721.5	$	650.4	$	-565.8	$	5,523.50
	Depreciation and Amortization		-488.7		-50.5		-100.9		-52		7.2		-684.9
	Other Operating Expenses		-2,952.40		-483.6		-199.1		-599		564.3		-3,669.80
	Operating Income/(Loss)		663.3		78.9		421.5		-0.6		5.7		1,168.80
	Interest Expense		-129.9		-24.8		-73.7		-26.3		4.1		-250.6
	Other Income, Net		12.6		0.7		8.5		866.2		-866.3		21.7
	Net Income Attributable to Controlling Interest	$	347.5	$	34.1	$	215.4	$	868.7	$	-857.1	$	608.6
	Cash Flows Used for Investments in Plant	$	501.9	$	91.2	$	458.2	$	22.5	$	-	$	1,073.80
	The following table summarizes NU's segmented total assets:
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	As of September 30, 2014	$	16,702.30	$	2,801.10	$	7,404.50	$	12,270.20	$	-11,195.80	$	27,982.30
	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)	9 Months Ended
	Sep. 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 and second quarter 2014 combined Quarterly Reports 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 September 30, 2014 and December 31, 2013, the results of operations and comprehensive income for the three and nine months ended September 30, 2014 and 2013, and the cash flows for the nine months ended September 30, 2014 and 2013. The results of operations and comprehensive income for the three and nine months ended September 30, 2014 and 2013, and the cash flows for the nine months ended September 30, 2014 and 2013 are not necessarily indicative of the results expected for a full year.
	NU consolidates CYAPC and YAEC because 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, and is also used to estimate the fair value of preferred stock and long-term debt.
	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 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. 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
	The Regulated companies purchase and procure energy and energy-related products, which are subject to price volatility, for their customers. 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. 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:
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 September 30, 2014, the mutual funds and equity investments were classified as Level 1 in the fair value hierarchy and totaled $58.2 million and $24.4 million, respectively. As of December 31, 2013, the mutual funds were classified as Level 1 and totaled $57.2 million. For the three months ended September 30, 2014 and 2013, net losses of $1.9 million and net gains of $3 million, respectively, were recorded in Other Income, Net. For the nine months ended September 30, 2014 and 2013, net gains of $1.9 million and $7.3 million, respectively, were recorded in Other Income, Net. 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 nine months ended September 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 unregulated 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)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Accounts Notes Loans And Financing Receivable Text Block	'
	(Millions of Dollars)	As of September 30, 2014		As of December 31, 2013
	NU	$	181.4	$	171.3
	CL&P		85.8		82
	NSTAR Electric		42.3		41.7
	PSNH		7.9		7.4
	WMECO		11.1		10

Other_Taxes_Tables

Other Taxes (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
State Of Connecticut Gross Earnings Taxes [Table Text Block]	'
		For the Three Months Ended				For the Nine Months Ended
	(Millions of Dollars)	30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	NU	$	35	$	37.5	$	114.6	$	108.9
	CL&P		32.5		35.5		99		97.3

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 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 September 30, 2014		As of September 30, 2013
	NU		$	128.9	$	122.9
	CL&P			52.2		36.6
	NSTAR Electric			18.1		31.9
	PSNH			21		16.9
	WMECO			10		13.8

REGULATORY_ACCOUNTING_Tables

REGULATORY ACCOUNTING (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Regulatory Assets Text Block	'
		As of September 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Benefit Costs	$	1,113.20		$	1,240.20
	Derivative Liabilities		427.5			638
	Income Taxes, Net		623.2			626.2
	Storm Restoration Costs		493.5			589.6
	Goodwill-related		510.5			525.9
	Regulatory Tracker Mechanisms		235.7			323.4
	Contractual Obligations - Yankee Companies		124.6			154.2
	Buy Out Agreements for Power Contracts		49.8			70.2
	Other Regulatory Assets		109.1			126.8
	Total Regulatory Assets		3,687.10			4,294.50
	Less: Current Portion		446			535.8
	Total Long-Term Regulatory Assets	$	3,241.10		$	3,758.70
			As of September 30, 2014									As of December 31, 2013
						NSTAR								NSTAR
	(Millions of Dollars)		CL&P			Electric		PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Benefit Costs		$	242.2		$	318.1	$	78.1	$	44.3	$	297.7	$	496.7	$	100.6	$	57.3
	Derivative Liabilities			421.1			4.3		-		-		630.4		7.7		-		-
	Income Taxes, Net			427.4			83.3		38.3		35.3		415.5		84		40.3		43.7
	Storm Restoration Costs			326			106.2		29.3		32		397.8		109.3		43.7		38.8
	Goodwill-related			-			438.3		-		-		-		451.5		-		-
	Regulatory Tracker Mechanisms			5.2			76.4		94.7		23.5		8		169.5		83.3		32.6
	Buy Out Agreements for Power Contracts			-			45.4		4.4		-		-		64.7		5.5		-
	Other Regulatory Assets			63.6			54.2		35.9		13.5		64.6		55.9		38.1		16.7
	Total Regulatory Assets			1,485.50			1,126.20		280.7		148.6		1,814.00		1,439.30		311.5		189.1
	Less: Current Portion			116.5			128.2		102.5		38.9		150.9		204.1		92.2		43
	Total Long-Term Regulatory Assets		$	1,369.00		$	998	$	178.2	$	109.7	$	1,663.10	$	1,235.20	$	219.3	$	146.1
Schedule Of Regulatory Liabilities Text Block	'
		As of September 30, 2014			As of December 31, 2013
	(Millions of Dollars)	NU			NU
	Cost of Removal	$	439.1		$	435.1
	Regulatory Tracker Mechanisms		339.9			151.2
	AFUDC - Transmission		67.2			68.1
	Other Regulatory Liabilities		62.7			52.9
	Total Regulatory Liabilities		908.9			707.3
	Less: Current Portion		399			204.3
	Total Long-Term Regulatory Liabilities	$	509.9		$	503
			As of September 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		$	22.5		$	260.7	$	49.2	$	-	$	29.1	$	250	$	49.7	$	-
	Regulatory Tracker Mechanisms			196.4			67.3		25.9		43.9		95.6		21.9		21.6		21.1
	AFUDC - Transmission			53.9			4.1		-		9.2		54.7		4.1		-		9.3
	Other Regulatory Liabilities			10.6			31.6		4.7		0.7		8.4		31.1		1		3.4
	Total Regulatory Liabilities			283.4			363.7		79.8		53.8		187.8		307.1		72.3		33.8
	Less: Current Portion			195.7			97.2		29.2		43.5		94		54		20.6		19.9
	Total Long-Term Regulatory Liabilities		$	87.7		$	266.5	$	50.6	$	10.3	$	93.8	$	253.1	$	51.7	$	13.9

PROPERTY_PLANT_AND_ACCUMULATED1

PROPERTY, PLANT AND ACCUMULATED DEPRECIATION (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Public Utility Property, Plant, and Equipment [Text Block]	'
				As of September 30, 2014			As of December 31, 2013
	(Millions of Dollars)			NU			NU
	Distribution - Electric			$	12,306.60		$	11,950.20
	Distribution - Natural Gas				2,494.50			2,425.90
	Transmission				6,564.20			6,412.50
	Generation				1,168.60			1,152.30
	Electric and Natural Gas Utility				22,533.90			21,940.90
	Other (1)				541.7			508.7
	Property, Plant and Equipment, Gross				23,075.60			22,449.60
	Less: Accumulated Depreciation
		Electric and Natural Gas Utility			-5,687.00			-5,387.00
		Other			-216.3			-196.2
	Total Accumulated Depreciation				-5,903.30			-5,583.20
	Property, Plant and Equipment, Net				17,172.30			16,866.40
	Construction Work in Progress				1,082.30			709.8
	Total Property, Plant and Equipment, Net			$	18,254.60		$	17,576.20
		As of September 30, 2014										As of December 31, 2013
					NSTAR									NSTAR
	(Millions of Dollars)	CL&P			Electric			PSNH		WMECO		CL&P		Electric		PSNH		WMECO
	Distribution	$	5,104.80		$	4,812.40		$	1,654.50	$	774.8	$	4,930.70	$	4,694.70	$	1,608.20	$	756.6
	Transmission		3,125.20			1,824.60			715.8		851.8		3,071.90		1,772.30		695.7		826.4
	Generation		-			-			1,134.70		33.9		-		-		1,131.20		21.1
	Property, Plant and Equipment, Gross		8,230.00			6,637.00			3,505.00		1,660.50		8,002.60		6,467.00		3,435.10		1,604.10
	Less: Accumulated Depreciation		-1,908.20			-1,726.70			-1,069.40		-291.8		-1,804.10		-1,631.30		-1,021.80		-271.5
	Property, Plant and Equipment, Net		6,321.80			4,910.30			2,435.60		1,368.70		6,198.50		4,835.70		2,413.30		1,332.60
	Construction Work in Progress		379			301.4			125		63.7		252.8		208.2		54.3		48.5
	Total Property, Plant and Equipment, Net	$	6,700.80		$	5,211.70		$	2,560.60	$	1,432.40	$	6,451.30	$	5,043.90	$	2,467.60	$	1,381.10

DERIVATIVE_INSTRUMENTS_Tables

DERIVATIVE INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Derivative Instruments In Statement Of Financial Position Fair Value Text Block	'
			As of September 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		$	-		$	0.4
	Level 3:
		NU (1)		17.4			-6.8			10.6
		CL&P (1)		16.4			-6.8			9.6
		NSTAR Electric		1			-			1
	Long-Term Derivative Assets:
	Level 3:
		NU (1)	$	96		$	-20.9		$	75.1
		CL&P (1)		95.1			-20.9			74.2
		NSTAR Electric		0.9			-			0.9
	Current Derivative Liabilities:
	Level 2:
		NU (1)	$	-2.4		$	0.4		$	-2
	Level 3:
		NU		-88.3			-			-88.3
		CL&P		-86.8			-			-86.8
		NSTAR Electric		-1.5			-			-1.5
	Long-Term Derivative Liabilities:
	Level 3:
		NU	$	-420.9		$	-		$	-420.9
		CL&P		-418.1			-			-418.1
		NSTAR Electric		-2.8			-			-2.8
			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 September 30,							For the Nine Months Ended September 30,
	(Millions of Dollars)			2014			2013				2014			2013
	NU
	Balance Sheets:
		Regulatory Assets and Liabilities		$	-15.7		$	0.3			$	149.9		$	48.8
	Statements of Income:
		Purchased Power, Fuel and Transmission			-			0.2				-			0.9
Rollforward Of Net Derivative Asset Liabilities Valued Using Unobservable Inputs [Table Text Block]	'
			For the Three Months Ended September 30,						For the Nine Months Ended September 30,
			2014			2013			2014			2013
	(Millions of Dollars)		NU			NU			NU			NU
	Derivatives, Net:
	Fair Value as of Beginning of Period		$	-430.9		$	-788.1		$	-635.2		$	-878.6
	Net Realized/Unrealized Gains Included in:
		Net Income		-			1.2			-			8.3
		Regulatory Assets and Liabilities		-13.6			0.8			147.6			49.6
	Settlements			21			21.3			64.1			55.9
	Fair Value as of End of Period		$	-423.5		$	-764.8		$	-423.5		$	-764.8
			For the Three Months Ended September 30,
			2014							2013
	(Millions of Dollars)		CL&P			NSTAR Electric				CL&P			NSTAR Electric
	Derivatives, Net:
	Fair Value as of Beginning of Period		$	-424.6		$	-6.3			$	-775.8		$	-13.1
	Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets and Liabilities			-15			1.4				-1.2			0.5
	Settlements			18.5			2.5				21.7			1
	Fair Value as of End of Period		$	-421.1		$	-2.4			$	-755.3		$	-11.6
			For the Nine Months Ended September 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			149.4			0.9				45.1			0.6
	Settlements			60.1			4				65.8			2.7
	Fair Value as of End of Period		$	-421.1		$	-2.4			$	-755.3		$	-11.6
Fairvalueinputsliabilitiesquantitativeinformationtabletextblock	'
		As of September 30, 2014									As of December 31, 2013
			Range						Period Covered			Range					Period Covered
	Energy Prices:
	NU	$	66	-	68	per MWh			2018 - 2020		$	49	-	77	per MWh		2018 - 2029
	CL&P	$	66	-	68	per MWh			2018 - 2020		$	56	-	58	per MWh		2018 - 2029
	Capacity Prices:
	NU	$	7.03	-	12.98		per kW-Month		2016 - 2026		$	5.07	-	11.82		per kW-Month	2017 - 2029
	CL&P	$	7.03	-	12.98		per kW-Month		2018 - 2026		$	5.07	-	10.42		per kW-Month	2017 - 2026
	NSTAR Electric	$	11	-	11.1		per kW-Month		2016 - 2019		$	5.07	-	7.38		per kW-Month	2017 - 2019
	Forward Reserve:
	NU, CL&P	$	5.8	-	9.5		per kW-Month		2014 - 2024		$	3.3	-	3.3		per kW-Month	2014 - 2024
	REC Prices:
	NU	$	41	-	70	per REC			2014 - 2018		$	36	-	87	per REC		2014 - 2029
	NSTAR Electric	$	41	-	70	per REC			2014 - 2018		$	36	-	70	per REC		2014 - 2018

MARKETABLE_SECURITIES_Tables

MARKETABLE SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Available For Sale Securities Reconciliation [Table TextBlock]	'
			As of September 30, 2014
						Pre-Tax			Pre-Tax
			Amortized			Unrealized			Unrealized
	(Millions of Dollars)		Cost			Gains			Losses			Fair Value
	NU
		Debt Securities (1)	$	310.6		$	7.8		$	-0.2		$	318.2
		Equity Securities (1)		160.9			71.1			-			232
	WMECO
		Debt Securities (2)		58.1			0.1			-0.1			58.1
			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)		$	47.6		$	47.6		$	21.9		$	22.1
	One to five years			91			91.4			30.7			30.5
	Six to ten years			65.6			67.5			1.4			1.4
	Greater than ten years			106.4			111.7			4.1			4.1
	Total Debt Securities		$	310.6		$	318.2		$	58.1		$	58.1
Fair Value Heirarchy [Table Text Block]	'
					NU						WMECO
					As of						As of
	(Millions of Dollars)				30-Sep-14			31-Dec-13			30-Sep-14			31-Dec-13
	Level 1:
		Mutual Funds and Equities			$	314.6		$	281.3		$	-		$	-
		Money Market Funds				27.1			32.9			4.4			10.9
	Total Level 1				$	341.7		$	314.2		$	4.4		$	10.9
	Level 2:
		U.S. Government Issued Debt Securities (Agency and Treasury)			$	56.5		$	61.4		$	-		$	6.8
		Corporate Debt Securities				61.2			53.6			14.1			15.1
		Asset-Backed Debt Securities				37.9			30.4			14.3			9
		Municipal Bonds				112.5			105.5			13.9			11.2
		Other Fixed Income Securities				23			15.8			11.4			4.9
	Total Level 2				$	291.1		$	266.7		$	53.7		$	47
	Total Marketable Securities				$	632.8		$	580.9		$	58.1		$	57.9

Recovered_Sheet1

Pension Benefits and Postretirement Benefits Other Than Pensions (Tables)	9 Months Ended
	Sep. 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 Nine Months Ended
		30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	19.1	$	25.6	$	60.7	$	76.7
	Interest Cost		56.4		51.7		169.5		155
	Expected Return on Plan Assets		-77.7		-69.5		-233.1		-208.5
	Actuarial Loss		31.7		52.4		96.5		158.1
	Prior Service Cost		1.1		1.1		3.3		3
	Total Net Periodic Benefit Expense	$	30.6	$	61.3	$	96.9	$	184.3
	Capitalized Pension Expense	$	8.3	$	18.3	$	26.7	$	54.9
		PBOP				PBOP
		For the Three Months Ended				For the Nine Months Ended
		30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	(Millions of Dollars)	NU		NU		NU		NU
	Service Cost	$	3.1	$	4.2	$	9.3	$	12.6
	Interest Cost		12.4		11.8		37.1		35.4
	Expected Return on Plan Assets		-15.8		-13.9		-47.4		-41.6
	Actuarial Loss		3		6.5		9.1		19.5
	Prior Service Credit		-0.7		-0.5		-2.1		-1.5
	Total Net Periodic Benefit Expense	$	2	$	8.1	$	6	$	24.4
	Capitalized PBOP Expense	$	1.1	$	2.6	$	1.9	$	7.6
		Pension and SERP
		For the Three Months Ended September 30, 2014								For the Three Months Ended September 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	$	8.3		3.3	$	1.2
	Interest Cost		12.5		10.3		5.7		2.5		12.1		14.5		5.8		2.5
	Expected Return on Plan Assets		-18.7		-15.7		-9.3		-4.4		-18.4		-21.1		-9.2		-4.3
	Actuarial Loss		8.2		5.9		2.8		1.7		13.9		14.4		5.4		2.9
	Prior Service Cost		0.4		-		0.1		0.1		0.4		-		0.1		0.1
	Total Net Periodic Benefit Expense	$	7.4	$	3.5	$	1.6	$	0.7	$	14.3	$	16.1	$	5.4	$	2.4
	Intercompany Allocations	$	6.5	$	2.9	$	1.8	$	1.2	$	11.4	$	-2.1	$	2.6	$	2
	Capitalized Pension Expense	$	4.3	$	2.6	$	0.7	$	0.6	$	7	$	9.8	$	1.7	$	1.3
		Pension and SERP
		For the Nine Months Ended September 30, 2014								For the Nine Months Ended September 30, 2013
				NSTAR								NSTAR
	(Millions of Dollars)	CL&P		Electric		PSNH		WMECO		CL&P		Electric(1)		PSNH		WMECO
	Service Cost	$	15.2	$	10.6	$	7.4	$	2.7	$	18.7	$	24.8	$	9.8	$	3.5
	Interest Cost		38.1		31		18		7.8		36.3		43.5		17.8		7.5
	Expected Return on Plan Assets		-56.7		-47.3		-28.8		-13.5		-55.4		-63.3		-26.2		-13
	Actuarial Loss		25.5		17.6		8.9		5.2		42		43.6		16.2		8.9
	Prior Service Cost/(Credit)		1.4		-		0.5		0.3		1.4		-0.2		0.4		0.3
	Total Net Periodic Benefit Expense	$	23.5	$	11.9	$	6	$	2.5	$	43	$	48.4	$	18	$	7.2
	Intercompany Allocations	$	20.8	$	6.7	$	6	$	3.9	$	33.6	$	-6.2	$	7.8	$	6
	Capitalized Pension Expense	$	13.6	$	5.5	$	2.4	$	2	$	21	$	21.6	$	5.6	$	3.9
		PBOP
		For the Three Months Ended September 30, 2014								For the Three Months Ended September 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	0.6	$	0.8	$	0.3	$	0.1	$	0.9	$	0.6	$	0.2
	Interest Cost		2		4.9		1.1		0.4		2		1		0.4
	Expected Return on Plan Assets		-2.6		-6.5		-1.4		-0.6		-2.5		-1.3		-0.6
	Actuarial Loss/(Gain)		1		-0.1		0.6		0.1		1.8		0.9		0.3
	Prior Service Credit		-		-0.5		-		-		-		-		-
	Total Net Periodic Benefit Expense/(Income)	$	1	$	-1.4	$	0.6	$	0	$	2.2	$	1.2	$	0.3
	Intercompany Allocations	$	0.9	$	0.3	$	0.2	$	0.2	$	1.7	$	0.4	$	0.3
	Capitalized PBOP Expense/(Income)	$	0.5	$	-0.5	$	0.2	$	-	$	1.3	$	0.4	$	0.3
		PBOP
		For the Nine Months Ended September 30, 2014								For the Nine Months Ended September 30, 2013
	(Millions of Dollars)	CL&P			NSTAR Electric		PSNH		WMECO	CL&P		PSNH		WMECO
	Service Cost	$	1.7	$	2.3	$	1	$	0.3	$	2.6	$	1.7	$	0.5
	Interest Cost		6		14.6		3.2		1.3		5.9		3.1		1.3
	Expected Return on Plan Assets		-7.9		-19.5		-4.1		-1.7		-7.6		-3.9		-1.7
Actuarial Loss/(Gain)		3.2		-0.4		1.7		0.3		5.6		2.7		0.8
Prior Service Credit		-		-1.4		-		-		-		-		-
Total Net Periodic Benefit Expense/(Income)	$	3	$	-4.4	$	1.8	$	0.2	$	6.5	$	3.6	$	0.9
Intercompany Allocations	$	3.1	$	0.4	$	0.8	$	0.6	$	5.3	$	1.2	$	1
Capitalized PBOP Expense/(Income)	$	1.5	$	-1.5	$	0.6	$	0.1	$	3.7	$	1.1	$	0.7

Environmental_Matters_Tables

Environmental Matters (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Environmental Loss Contingencies By Site Text Block	'
		As of September 30, 2014				As of December 31, 2013
				Reserve				Reserve
		Number of Sites		(in millions)		Number of Sites		(in millions)
	NU		65	$	34.7		68	$	35.4
	CL&P		16		4		18		3.4
	NSTAR Electric		13		1.1		12		1.2
	PSNH		13		5.3		15		5.4
	WMECO		4		0.5		5		0.4

LongTerm_Contractual_Arrangeme

Long-Term Contractual Arrangements (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Long-term Purchase Commitment [Table Text Block]	'
		October - December
	(Millions of Dollars)	2014		2015		2016		2017		2018		Thereafter		Total
	CL&P	$	20	$	60.7	$	66.1	$	67	$	67.7	$	717	$	998.5
	NSTAR Electric		21.8		86.3		100		96.1		59.6		377.6		741.4
	WMECO		-		-		2.4		2.4		2.4		28.9		36.1

Guarantees_and_Indemnification

Guarantees and Indemnifications (Tables)	9 Months Ended
	Sep. 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	$	64.3	2014 - 2016 (1)
	Various	New England Hydro Companies' Long-Term Debt	$	2	Unspecified
	NUSCO and RRR	Lease Payments for Vehicles and Real Estate	$	15.3	2019 and 2024

Other_Contingencies_Tables

Other Contingencies (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Loss Contingencies By Contingency [Table Text Block]	'
		NU
			Third Quarter		Second Quarter
	(Millions of Dollars)		2013		2014	Total
	1st Complaint - Base ROE	$	23.7	$	1.2	$	24.9
	2nd Complaint - Base ROE		-		27.4		27.4
	Incentive ROE (1st and 2nd Complaint)		-		23.8		23.8
	Cumulative Reserve	$	23.7	$	52.4	$	76.1
		CL&P						NSTAR Electric
			Third Quarter		Second Quarter				Third Quarter		Second Quarter
	(Millions of Dollars)		2013		2014	Total			2013		2014	Total
	1st Complaint - Base ROE	$	12.8	$	0.5	$	13.3	$	5.7	$	0.4	$	6.1
	2nd Complaint - Base ROE		-		13.5		13.5		-		7.5		7.5
	Incentive ROE (1st and 2nd Complaint)		-		16.1		16.1		-		2		2
	Cumulative Reserve	$	12.8	$	30.1	$	42.9	$	5.7	$	9.9	$	15.6
		PSNH						WMECO
			Third Quarter		Second Quarter				Third Quarter		Second Quarter
	(Millions of Dollars)		2013		2014	Total			2013		2014	Total
	1st Complaint - Base ROE	$	2.3	$	0.1	$	2.4	$	2.9	$	0.2	$	3.1
	2nd Complaint - Base ROE		-		2.7		2.7		-		3.7		3.7
	Incentive ROE (1st and 2nd Complaint)		-		0.8		0.8		-		4.9		4.9
	Cumulative Reserve	$	2.3	$	3.6	$	5.9	$	2.9	$	8.8	$	11.7

FAIR_VALUE_OF_FINANCIAL_INSTRU1

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Fair Value By Balance Sheet Grouping Text Block	'
		As of September 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	$	151	$	155.6	$	152.7
	Long-Term Debt		8,412.60		8,876.30		8,310.20		8,443.10
		As of September 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	$	110.1	$	43	$	40.9	$	-	$	-	$	-	$	-
	Long-Term Debt		2,841.80		3,189.50		1,797.40		1,959.40		999.2		1,046.40		628.7		667.4
		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)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule Of Accumulated Other Comprehensive Income Loss Table Text Block	'
			For the Nine Months Ended September 30, 2014												For the Nine Months Ended September 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			-			0.2			1.2			1.4			-		-0.8		-		-0.8
	Amounts Reclassified from AOCI			1.5			-			2.9			4.4			1.5		-		4.8		6.3
	Net OCI			1.5			0.2			4.1			5.8			1.5		-0.8		4.8		5.5
	AOCI as of End of Period		$	-12.9		$	0.6		$	-27.9		$	-40.2		$	-14.9	$	0.5	$	-53	$	-67.4
		For the Three Months Ended						For the Nine Months Ended
		September 30,						September 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		$	-2.5		$	-2.5		Interest Expense
	Tax Benefit		0.3			0.3			1			1		Income Tax Expense
	Qualified Cash Flow Hedging Instruments, Net of Tax	$	-0.5		$	-0.5		$	-1.5		$	-1.5
	Pension, SERP and PBOP Benefit Plan Costs:
	Amortization of Actuarial Losses	$	-1.6		$	-2.5		$	-4.7		$	-7.3		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		-1.6			-2.5			-4.8			-7.4
	Tax Benefit		0.6			0.9			1.9			2.6		Income Tax Expense
	Pension, SERP and PBOP Benefit Plan Costs, Net of Tax	$	-1		$	-1.6		$	-2.9		$	-4.8
	Total Amounts Reclassified from AOCI, Net of Tax	$	-1.5		$	-2.1		$	-4.4		$	-6.3

COMMON_SHARES_Tables

COMMON SHARES (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Schedule of Stock by Class [Text Block]	'
	12.       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		September 30, 2014 and	Issued as of
		Par Value		31-Dec-13	30-Sep-14	31-Dec-13
	NU	$	5	380,000,000	333,353,446	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 September 30, 2014 and December 31, 2013, there were 16,730,815 and 17,796,672 NU common shares held as treasury shares, respectively. As of September 30, 2014 and December 31, 2013, NU common shares outstanding were 316,622,631 and 315,273,559, respectively.

COMMON_SHARESHOLDERS_EQUITY_AN1

COMMON SHARESHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (NU) (Tables)	9 Months Ended
	Sep. 30, 2014
Notes To Consolidated Financial Statements [Abstract]	'
Minority Interest Disclosure Text Block	'
	13	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-Sep-14				30-Sep-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		$	9,753.80	$	155.6	$	9,406.60	$	155.6
	Net Income			236.5		-		211.4		-
	Dividends on Common Shares			-124.2		-		-114.9		-
	Dividends on Preferred Stock			-1.9		-1.9		-1.9		-1.9
	Issuance of Common Shares			1		-		1.4		-
	Other Transactions, Net			24.1		-		12.8		-
	Net Income Attributable to Noncontrolling Interests			-		1.9		-		1.9
	Other Comprehensive Income			1.3		-		2.1		-
	Balance as of End of Period		$	9,890.60	$	155.6	$	9,517.50	$	155.6
			For the Nine Months Ended
			30-Sep-14				30-Sep-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			603.6		-		614.4		-
	Dividends on Common Shares			-372.2		-		-346.9		-
	Dividends on Preferred Stock			-5.6		-5.6		-5.8		-5.8
	Issuance of Common Shares			6.4		-		10.2		-
	Other Transactions, Net			41		-		3		-
	Net Income Attributable to Noncontrolling Interests			-		5.6		-		5.8
	Other Comprehensive Income			5.9		-		5.5		-
	Balance as of End of Period		$	9,890.60	$	155.6	$	9,517.50	$	155.6

EARNINGS_PER_SHARE_Tables

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 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 Nine Months Ended
	(Millions of Dollars, except share information)		30-Sep-14		30-Sep-13		30-Sep-14		30-Sep-13
	Net Income Attributable to Controlling Interest		$	234.6	$	209.5	$	597.9	$	608.6
	Weighted Average Common Shares Outstanding:
		Basic		316,340,691		315,291,346		315,941,904		315,191,752
		Dilutive Effect		1,214,234		926,893		1,244,586		869,379
		Diluted		317,554,925		316,218,239		317,186,490		316,061,131
	Basic and Diluted EPS		$	0.74	$	0.66	$	1.89	$	1.93

SEGMENT_INFORMATION_Tables

SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting Information [Line Items]	'
Schedule Of Segment Reporting Information By Segment Text Block	'
		For the Three Months Ended September 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,502.60	$	109.2	$	262.5	$	211.2	$	-193	$	1,892.50
	Depreciation and Amortization		-71.7		-16.4		-37.4		-13.8		8.6		-130.7
	Other Operating Expenses		-1,141.50		-98.4		-74.2		-192.4		185.6		-1,320.90
	Operating Income/(Loss)		289.4		-5.6		150.9		5		1.2		440.9
	Interest Expense		-49.2		-8.5		-24.5		-8.6		1		-89.8
	Other Income, Net		9.3		0.1		2.7		226.4		-226.6		11.9
	Net Income Attributable to Controlling Interest	$	153.4	$	-9.9	$	88.1	$	228.3	$	-225.3	$	234.6
		For the Nine Months Ended September 30, 2014
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	4,350.40	$	737.5	$	721.4	$	568.1	$	-516.7	$	5,860.70
	Depreciation and Amortization		-309.9		-51.1		-111.4		-28.3		12.7		-488
	Other Operating Expenses		-3,343.90		-586.2		-211.5		-534.1		505.6		-4,170.10
	Operating Income		696.6		100.2		398.5		5.7		1.6		1,202.60
	Interest Expense		-143.8		-25.6		-78.8		-27.2		3.2		-272.2
	Other Income, Net		13.6		0.2		6.9		657.9		-659.5		19.1
	Net Income Attributable to Controlling Interest	$	349.1	$	44.2	$	206.8	$	653.4	$	-655.6	$	597.9
	Cash Flows Used for Investments in Plant	$	480.1	$	120.6	$	469.9	$	46.9	$	-	$	1,117.50
		For the Three Months Ended September 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	1,508.60	$	97.1	$	234.1	$	212.5	$	-159.7	$	1,892.60
	Depreciation and Amortization		-159.6		-16.4		-34.5		-11.2		2.6		-219.1
	Other Operating Expenses		-1,064.10		-89.4		-73.4		-206.8		159.5		-1,274.20
	Operating Income/(Loss)		284.9		-8.7		126.2		-5.5		2.4		399.3
	Interest Expense		-44.3		-8.6		-26.6		-9.2		1.2		-87.5
	Other Income, Net		5.5		0.5		2.9		312.1		-312.1		8.9
	Net Income/(Loss) Attributable to Controlling Interest	$	156.9	$	-10.4	$	58.6	$	313.1	$	-308.7	$	209.5
		For the Nine Months Ended September 30, 2013
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	Operating Revenues	$	4,104.40	$	613	$	721.5	$	650.4	$	-565.8	$	5,523.50
	Depreciation and Amortization		-488.7		-50.5		-100.9		-52		7.2		-684.9
	Other Operating Expenses		-2,952.40		-483.6		-199.1		-599		564.3		-3,669.80
	Operating Income/(Loss)		663.3		78.9		421.5		-0.6		5.7		1,168.80
	Interest Expense		-129.9		-24.8		-73.7		-26.3		4.1		-250.6
	Other Income, Net		12.6		0.7		8.5		866.2		-866.3		21.7
	Net Income Attributable to Controlling Interest	$	347.5	$	34.1	$	215.4	$	868.7	$	-857.1	$	608.6
	Cash Flows Used for Investments in Plant	$	501.9	$	91.2	$	458.2	$	22.5	$	-	$	1,073.80
	The following table summarizes NU's segmented total assets:
		Electric		Natural Gas
	(Millions of Dollars)	Distribution		Distribution		Transmission		Other		Eliminations		Total
	As of September 30, 2014	$	16,702.30	$	2,801.10	$	7,404.50	$	12,270.20	$	-11,195.80	$	27,982.30
	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)	9 Months Ended
	Sep. 30, 2014
Description of Consolidation of Yankee Companies	'NU consolidates CYAPC and YAEC because 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 $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	$181.40	$171.30
The Connecticut Light And Power Company [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	85.8	82
NSTAR Electric Company [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	42.3	41.7
Public Service Company Of New Hampshire [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	7.9	7.4
Western Massachusetts Electric Company [Member]	'	'
Accounts Notes And Loans Receivable [Line Items]	'	'
Allowance For Doubtful Accounts Receivable Current	$11.10	$10

Other_Taxes_Details

Other Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Excise And Sales Taxes	$35	$37.50	$114.60	$108.90
The Connecticut Light And Power Company [Member]	'	'	'	'
Excise And Sales Taxes	$32.50	$35.50	$99	$97.30

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Capital Expenditures Incurred But Not Yet Paid	$128.90	$122.90
The Connecticut Light And Power Company [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	52.2	36.6
NSTAR Electric Company [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	18.1	31.9
Public Service Company Of New Hampshire [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	21	16.9
Western Massachusetts Electric Company [Member]	'	'
Capital Expenditures Incurred But Not Yet Paid	$10	$13.80

Severance_Benefits_Details

Severance Benefits (Details) (USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Notes To Consolidated Financial Statements [Abstract]	'	'	'	'
Description Of Postemployment Benefits	'	'Severance Benefits NU recorded severance benefit expenses of $0.7 million and $6.5 million associated with the partial outsourcing of information technology functions and ongoing post-merger integration for the three and nine months ended September 30, 2014, respectively, and $9.2 million for the three and nine months ended September 30, 2013. As of September 30, 2014 and December 31, 2013, the severance accrual totaled $6.4 million and $14.7 million, respectively, and was included in Other Current Liabilities on the balance sheets.	'	'
Postemployment Benefits Period Expense	$0.70	$6.50	$9.20	'
Postemployment Benefits Liability Current And Noncurrent	$6.40	$6.40	'	$14.70

REGULATORY_ACCOUNTING_Details

REGULATORY ACCOUNTING (Details) (USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	$3,687,100,000	$4,294,500,000
Regulatory Assets Current	445,962,000	535,791,000
Regulatory Assets Long Term	3,241,122,000	3,758,694,000
Regulatory Assets And Liabilities Other Disclosures Abstract	'	'
Amount of Regulatory Costs Not yet Approved	64,700,000	65,100,000
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 (with carrying charges) associated with five major storms that occurred in 2011 and 2012. CL&P will recover these costs in its distribution rates over a six-year period beginning December 1, 2014. Effective June 1, 2014, CL&P received $65.4 million of DOE Phase II Damages proceeds. On June 17, 2014, the PURA ordered CL&P to refund these proceeds to customers by offsetting the deferred storm restoration costs regulatory asset. For further information on the DOE Phase II Damages proceeds received from the Yankee Companies, see Note 9C, "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 9E, "Commitments and Contingencies – FERC Base ROE Complaints," in the second quarter of 2014 the Company had recorded a series of reserves at its electric subsidiaries to recognize the potential financial impact of these rulings. As of September 30, 2014, the cumulative pre-tax reserves (excluding interest) totaled $76.1 million at NU, $42.9 million at CL&P, $15.6 million at NSTAR Electric, $5.9 million at PSNH and $11.7 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 (excluding interest) of $23.7 million at NU, $12.8 million at CL&P, $5.7 million at NSTAR Electric, $2.3 million at PSNH and $2.9 million at WMECO. These reserves were recorded in each electric subsidiary's respective transmission regulatory tracker mechanism and as a reduction of Operating Revenues. Effective June 1, 2014, as a result of damages awarded to the Yankee Companies for spent nuclear fuel lawsuits against the DOE described in Note 9C, "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. 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. Refunds to customers for these DOE proceeds began in the third quarter of 2014.	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	908,900,000	707,300,000
Regulatory Liability Current	398,985,000	204,278,000
Regulatory Liabilities Long-Term	509,889,000	502,984,000
Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	439,100,000	435,100,000
Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	339,900,000	151,200,000
AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	67,200,000	68,100,000
Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	62,700,000	52,900,000
The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	1,485,500,000	1,814,000,000
Regulatory Assets Current	116,531,000	150,943,000
Regulatory Assets Long Term	1,369,025,000	1,663,147,000
Regulatory Assets And Liabilities Other Disclosures Abstract	'	'
Amount of Regulatory Costs Not yet Approved	3,200,000	7,300,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	283,400,000	187,800,000
Regulatory Liability Current	195,663,000	93,961,000
Regulatory Liabilities Long-Term	87,696,000	93,757,000
The Connecticut Light And Power Company [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	22,500,000	29,100,000
The Connecticut Light And Power Company [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	196,400,000	95,600,000
The Connecticut Light And Power Company [Member] | AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	53,900,000	54,700,000
The Connecticut Light And Power Company [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	10,600,000	8,400,000
NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	1,126,200,000	1,439,300,000
Regulatory Assets Current	128,205,000	204,144,000
Regulatory Assets Long Term	998,030,000	1,235,156,000
Regulatory Assets And Liabilities Other Disclosures Abstract	'	'
Amount of Regulatory Costs Not yet Approved	36,000,000	33,400,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	363,700,000	307,100,000
Regulatory Liability Current	97,215,000	53,958,000
Regulatory Liabilities Long-Term	266,524,000	253,108,000
NSTAR Electric Company [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	260,700,000	250,000,000
NSTAR Electric Company [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	67,300,000	21,900,000
NSTAR Electric Company [Member] | AFUDC Transmission Incentive [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	4,100,000	4,100,000
NSTAR Electric Company [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	31,600,000	31,100,000
Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	280,700,000	311,500,000
Regulatory Assets Current	102,473,000	92,194,000
Regulatory Assets Long Term	178,204,000	219,346,000
Regulatory Assets And Liabilities Other Disclosures Abstract	'	'
Amount of Regulatory Costs Not yet Approved	0	0
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	79,800,000	72,300,000
Regulatory Liability Current	29,165,000	20,643,000
Regulatory Liabilities Long-Term	50,614,000	51,723,000
Public Service Company Of New Hampshire [Member] | Cost Of Removal [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	49,200,000	49,700,000
Public Service Company Of New Hampshire [Member] | Regulatory Tracker Deferrals Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	25,900,000	21,600,000
Public Service Company Of New Hampshire [Member] | Other Regulatory Liabilities [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	4,700,000	1,000,000
Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	148,600,000	189,100,000
Regulatory Assets Current	38,907,000	43,024,000
Regulatory Assets Long Term	109,690,000	146,088,000
Regulatory Assets And Liabilities Other Disclosures Abstract	'	'
Amount of Regulatory Costs Not yet Approved	11,200,000	10,100,000
Regulatory Liabilities [Line Items]	'	'
Regulatory Liabilities, Total	53,800,000	33,800,000
Regulatory Liability Current	43,462,000	19,858,000
Regulatory Liabilities Long-Term	10,289,000	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	43,900,000	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	1,113,200,000	1,240,200,000
Benefit Costs [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	242,200,000	297,700,000
Benefit Costs [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	318,100,000	496,700,000
Benefit Costs [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	78,100,000	100,600,000
Benefit Costs [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	44,300,000	57,300,000
Regulatory Assets Offsetting Derivative Liabilities [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	427,500,000	638,000,000
Regulatory Assets Offsetting Derivative Liabilities [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	421,100,000	630,400,000
Regulatory Assets Offsetting Derivative Liabilities [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	4,300,000	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	623,200,000	626,200,000
Deferred Income Tax Charges Member | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	427,400,000	415,500,000
Deferred Income Tax Charges Member | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	83,300,000	84,000,000
Deferred Income Tax Charges Member | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	38,300,000	40,300,000
Deferred Income Tax Charges Member | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	35,300,000	43,700,000
Storm Restoration Costs [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	493,500,000	589,600,000
Storm Restoration Costs [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	326,000,000	397,800,000
Storm Restoration Costs [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	106,200,000	109,300,000
Storm Restoration Costs [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	29,300,000	43,700,000
Storm Restoration Costs [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	32,000,000	38,800,000
Goodwill Regulatory Asset [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	510,500,000	525,900,000
Goodwill Regulatory Asset [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	438,300,000	451,500,000
Regulatory Tracker Deferrals Regulatory Assets [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	235,700,000	323,400,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	5,200,000	8,000,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	76,400,000	169,500,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	94,700,000	83,300,000
Regulatory Tracker Deferrals Regulatory Assets [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	23,500,000	32,600,000
Unrecovered Contractual Obligations [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	124,600,000	154,200,000
Power Contracts Buy Out Agreements [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	49,800,000	70,200,000
Power Contracts Buy Out Agreements [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	45,400,000	64,700,000
Power Contracts Buy Out Agreements [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	4,400,000	5,500,000
Other Regulatory Assets [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	109,100,000	126,800,000
Other Regulatory Assets [Member] | The Connecticut Light And Power Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	63,600,000	64,600,000
Other Regulatory Assets [Member] | NSTAR Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	54,200,000	55,900,000
Other Regulatory Assets [Member] | Public Service Company Of New Hampshire [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	35,900,000	38,100,000
Other Regulatory Assets [Member] | Western Massachusetts Electric Company [Member]	'	'
Regulatory Asset [Line Items]	'	'
Regulatory Assets, Total	$13,500,000	$16,700,000

PROPERTY_PLANT_AND_ACCUMULATED2

PROPERTY, PLANT AND ACCUMULATED DEPRECIATION (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	$12,306,600,000	$11,950,200,000
Public Utilities Property Plant And Equipment Distribution Natural Gas	2,494,500,000	2,425,900,000
Public Utilities Property Plant And Equipment Transmission	6,564,200,000	6,412,500,000
Public Utilities Property Plant And Equipment Generation Or Processing	1,168,600,000	1,152,300,000
Public Utilities Property Plant And Equipment Electric And Natural Gas Utility Total	22,533,900,000	21,940,900,000
Public Utilities Property Plant And Equipment Other Property Plant And Equipment	541,700,000	508,700,000
Public Utilities Property Plant And Equipment Plant In Service	23,075,600,000	22,449,600,000
Electric And Natural Gas Utility Accumulated Depreciation	-5,687,000,000	-5,387,000,000
Other Accumulated Depreciation	-216,300,000	-196,200,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-5,903,300,000	-5,583,200,000
Property Plant And Equipment Net Excluding Construction Work In Progress	17,172,300,000	16,866,400,000
Public Utilities Property Plant And Equipment Construction Work In Progress	1,082,300,000	709,800,000
Property, Plant and Equipment, Net	18,254,610,000	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	5,104,800,000	4,930,700,000
Public Utilities Property Plant And Equipment Transmission	3,125,200,000	3,071,900,000
Public Utilities Property Plant And Equipment Generation Or Processing	0	0
Public Utilities Property Plant And Equipment Plant In Service	8,230,000,000	8,002,600,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-1,908,200,000	-1,804,100,000
Property Plant And Equipment Net Excluding Construction Work In Progress	6,321,800,000	6,198,500,000
Public Utilities Property Plant And Equipment Construction Work In Progress	379,000,000	252,800,000
Property, Plant and Equipment, Net	6,700,798,000	6,451,259,000
NSTAR Electric Company [Member]	'	'
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	4,812,400,000	4,694,700,000
Public Utilities Property Plant And Equipment Transmission	1,824,600,000	1,772,300,000
Public Utilities Property Plant And Equipment Generation Or Processing	0	0
Public Utilities Property Plant And Equipment Plant In Service	6,637,000,000	6,467,000,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-1,726,700,000	-1,631,300,000
Property Plant And Equipment Net Excluding Construction Work In Progress	4,910,300,000	4,835,700,000
Public Utilities Property Plant And Equipment Construction Work In Progress	301,400,000	208,200,000
Property, Plant and Equipment, Net	5,211,681,000	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	1,654,500,000	1,608,200,000
Public Utilities Property Plant And Equipment Transmission	715,800,000	695,700,000
Public Utilities Property Plant And Equipment Generation Or Processing	1,134,700,000	1,131,200,000
Public Utilities Property Plant And Equipment Plant In Service	3,505,000,000	3,435,100,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-1,069,400,000	-1,021,800,000
Property Plant And Equipment Net Excluding Construction Work In Progress	2,435,600,000	2,413,300,000
Public Utilities Property Plant And Equipment Construction Work In Progress	125,000,000	54,300,000
Property, Plant and Equipment, Net	2,560,635,000	2,467,556,000
Western Massachusetts Electric Company [Member]	'	'
Public Utility Property Plant And Equipment [Line Items]	'	'
Public Utilities Property Plant And Equipment Distribution	774,800,000	756,600,000
Public Utilities Property Plant And Equipment Transmission	851,800,000	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	1,660,500,000	1,604,100,000
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	-291,800,000	-271,500,000
Property Plant And Equipment Net Excluding Construction Work In Progress	1,368,700,000	1,332,600,000
Public Utilities Property Plant And Equipment Construction Work In Progress	63,700,000	48,500,000
Property, Plant and Equipment, Net	$1,432,368,000	$1,381,060,000

DERIVATIVE_INSTURMENTS_Details

DERIVATIVE INSTURMENTS (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Liabilities, Noncurrent	($420,931,000)	'	($420,931,000)	'	($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 September 30, 2014 and December 31, 2013, NU had NYMEX future contracts in order to reduce variability associated with the purchase price of approximately 9.7 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	'	200,000	'	900,000	'
Derivative Instruments Gain Loss Recognized In Regulatory Asset Liability	-15,700,000	300,000	149,900,000	48,800,000	'
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	-86,759,000	'	-86,759,000	'	-92,233,000
Derivative Liabilities, Noncurrent	-418,137,000	'	-418,137,000	'	-617,072,000
Fair Value Inputs Level 2 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	400,000	'	400,000	'	1,600,000
Derivative Liabilities - Current	-2,000,000	'	-2,000,000	'	'
Derivative Assets Noncurrent	'	'	'	'	200,000
Fair Value Inputs Level 3 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	10,600,000	'	10,600,000	'	8,600,000
Derivative Liabilities - Current	-88,300,000	'	-88,300,000	'	-93,700,000
Derivative Liabilities, Noncurrent	-420,900,000	'	-420,900,000	'	-624,100,000
Derivative Assets Noncurrent	75,100,000	'	75,100,000	'	74,000,000
Fair Value Inputs Level 3 [Member] | MinimumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	7.03	'	7.03	'	5.07
FairValueInputsEnergyPrices	66	'	66	'	49
FairValueInputsRenewableEnergyCreditPrices	41	'	41	'	36
FairValueInputsForwardReserve	5.8	'	5.8	'	3.3
Fair Value Inputs Level 3 [Member] | MaximumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	12.98	'	12.98	'	11.82
FairValueInputsEnergyPrices	68	'	68	'	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	9,600,000	'	9,600,000	'	7,300,000
Derivative Liabilities - Current	-86,800,000	'	-86,800,000	'	-92,200,000
Derivative Liabilities, Noncurrent	-418,100,000	'	-418,100,000	'	-617,100,000
Derivative Assets Noncurrent	74,200,000	'	74,200,000	'	71,400,000
Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member] | MinimumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	7.03	'	7.03	'	5.07
FairValueInputsEnergyPrices	66	'	66	'	56
FairValueInputsForwardReserve	5.8	'	5.8	'	3.3
Fair Value Inputs Level 3 [Member] | The Connecticut Light And Power Company [Member] | MaximumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	12.98	'	12.98	'	10.42
FairValueInputsEnergyPrices	68	'	68	'	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	1,000,000	'	1,000,000	'	1,200,000
Derivative Liabilities - Current	-1,500,000	'	-1,500,000	'	-1,500,000
Derivative Liabilities, Noncurrent	-2,800,000	'	-2,800,000	'	-7,000,000
Derivative Assets Noncurrent	900,000	'	900,000	'	'
Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member] | MinimumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	11	'	11	'	5.07
FairValueInputsRenewableEnergyCreditPrices	41	'	41	'	36
Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member] | MaximumMember	'	'	'	'	'
FairValueInputsQuantitativeInformation[Abstract]	'	'	'	'	'
FairValueInputsCapacityPrices	11.1	'	11.1	'	7.38
FairValueInputsRenewableEnergyCreditPrices	70	'	70	'	70
Netting And Collateral [Member] | Fair Value Inputs Level 2 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	0	'	0	'	-300,000
Derivative Liabilities - Current	400,000	'	400,000	'	'
Netting And Collateral [Member] | Fair Value Inputs Level 3 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	-6,800,000	'	-6,800,000	'	-9,800,000
Derivative Assets Noncurrent	-20,900,000	'	-20,900,000	'	-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	-6,800,000	'	-6,800,000	'	-9,800,000
Derivative Assets Noncurrent	-20,900,000	'	-20,900,000	'	-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	-2,400,000	'	-2,400,000	'	'
Derivative Assets Noncurrent	'	'	'	'	200,000
Commodity [Member] | Fair Value Inputs Level 3 [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	17,400,000	'	17,400,000	'	18,400,000
Derivative Liabilities - Current	-88,300,000	'	-88,300,000	'	-93,700,000
Derivative Liabilities, Noncurrent	-420,900,000	'	-420,900,000	'	-624,100,000
Derivative Assets Noncurrent	96,000,000	'	96,000,000	'	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	-86,800,000	'	-86,800,000	'	-92,200,000
Derivative Liabilities, Noncurrent	-418,100,000	'	-418,100,000	'	-617,100,000
Derivative Assets Noncurrent	95,100,000	'	95,100,000	'	113,600,000
Commodity [Member] | Fair Value Inputs Level 3 [Member] | NSTAR Electric Company [Member]	'	'	'	'	'
Derivative Instrument Detail Abstract	'	'	'	'	'
Derivative Assets - Current	1,000,000	'	1,000,000	'	1,200,000
Derivative Liabilities - Current	-1,500,000	'	-1,500,000	'	-1,500,000
Derivative Liabilities, Noncurrent	-2,800,000	'	-2,800,000	'	-7,000,000
Derivative Assets Noncurrent	$900,000	'	$900,000	'	'

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	($430.90)	($788.10)	($635.20)	($878.60)
Net Realized/Unrealized Gains Losses included in Net Income	0	1.2	'	8.3
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability	-13.6	0.8	147.6	49.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	21	21.3	64.1	55.9
Ending Balance	-423.5	-764.8	-423.5	-764.8
The Connecticut Light And Power Company [Member]	'	'	'	'
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	-424.6	-775.8	-630.6	-866.2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability	-15	-1.2	149.4	45.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	18.5	21.7	60.1	65.8
Ending Balance	-421.1	-755.3	-421.1	-755.3
NSTAR Electric Company [Member]	'	'	'	'
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]	'	'	'	'
Beginning Balance	-6.3	-13.1	-7.3	-14.9
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Reg Asset Liability	1.4	0.5	0.9	0.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	2.5	1	4	2.7
Ending Balance	($2.40)	($11.60)	($2.40)	($11.60)

MARKETABLE_SECURITIES_Details

MARKETABLE SECURITIES (Details) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 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

$58.20

'

$58.20

'

$57.20

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investments, Debt and Equity Securities [Abstract]

'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Fair Value Disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

318.2

299.6

58.1

57.9

232

224.1

Available-for-sale Securities, Gross Unrealized Gains

'

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'

'

'

'

'

'

'

'

'

'

'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7.8

2.5

0.1

0

71.1

60.5

AvailableForSaleSecuritiesGrossUnrealizedLoss

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

-0.2

-2.1

-0.1

0

'

'

Available For Sale Securities Amortized Cost

'

'

'

'

'

'

'

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'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

310.6

299.2

58.1

57.9

160.9

163.6

Marketable Securities, Restricted

447.7

'

447.7

'

424

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

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'

'

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'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities Fair Value Abstract

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

67.5

'

67.5

'

'

1.4

'

'

'

'

'

'

'

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'

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'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available For Sale Securities Debt Maturities After Ten Years Fair Value

111.7

'

111.7

'

'

4.1

'

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

'

'

'

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

91.4

'

91.4

'

'

30.5

'

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'

'

'

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'

'

Available For Sale Securities Debt Maturities Within One Year Fair Value

47.6

'

47.6

'

'

22.1

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'

'

Available For Sale Securities Debt Maturities Fair Value

318.2

'

318.2

'

'

58.1

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'

Available For Sale Securities Debt Maturities Amortized Cost Abstract

'

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'

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

91

'

91

'

'

30.7

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Available For Sale Securities Debt Maturities Within One Year Amortized Cost

47.6

'

47.6

'

'

21.9

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Available For Sale Securities Debt Maturities After Ten Years Amortized Cost

106.4

'

106.4

'

'

4.1

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'

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

65.6

'

65.6

'

'

1.4

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'

'

Available For Sale Securities Debt Maturities Amortized Cost

310.6

'

310.6

'

'

58.1

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'

'

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'

Fair Value Assets And Liabilities Measured On Recurring Basis Abstract

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Investments Fair Value Disclosure

632.8

'

632.8

'

580.9

58.1

57.9

341.7

314.2

4.4

10.9

291.1

266.7

53.7

47

56.5

61.4

0

6.8

61.2

53.6

14.1

15.1

37.9

30.4

14.3

9

112.5

105.5

13.9

11.2

23

15.8

11.4

4.9

27.1

32.9

4.4

10.9

314.6

281.3

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TradingSecuritiesEquity

24.4

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24.4

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IncreaseDecreaseInTradingSecurities

($1.90)

$3

$1.90

$7.30

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SHORT_TERM_AND_LONG_TERM_DEBT_

SHORT TERM AND LONG TERM DEBT (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Remaining Borrowing Capacity	$485,500,000	$435,500,000
Line of Credit Facility, Amount Outstanding	964,500,000	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 extended the expiration date of their joint $1.45 billion revolving credit facility for one 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 September 30, 2014 and December 31, 2013, NU had $964.5 million and $1.01 billion, respectively, in short-term borrowings outstanding under the NU parent commercial paper program, leaving $485.5 million and $435.5 million of available borrowing capacity as of September 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of September 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 September 30, 2014, there were intercompany loans from NU of $105.4 million to CL&P, $153.3 million to PSNH and $13.2 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 extended the expiration date of its $450 million revolving credit facility for one additional year to September 6, 2019. This facility serves to backstop NSTAR Electric's existing $450 million commercial paper program. As of September 30, 2014 and December 31, 2013, NSTAR Electric had $159.5 million and $103.5 million, respectively, in short-term borrowings outstanding under its commercial paper program, leaving $290.5 million and $346.5 million of available borrowing capacity as of September 30, 2014 and December 31, 2013, respectively. The weighted-average interest rate on these borrowings as of September 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.	'
Notes Payable	1,046,961,000	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. As the debt issuance refinanced short-term debt, the short-term debt was 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 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 borrowings. On September 15, 2014, CL&P repaid at maturity the $150 million of 4.80 percent 2004 Series A First Mortgage Bonds. On October 14, 2014, PSNH issued $75 million of first mortgage bonds at a yield of 3.144 percent that will mature on November 1, 2023. The first mortgage bonds are part of the same series of PSNH’s existing 3.50 percent Series S First Mortgage Bonds that were initially issued in November 2013. As a result, the aggregate principal amount of PSNH’s outstanding Series S First Mortgage Bonds totals $325 million. The proceeds, net of issuance costs, were used to repay short-term borrowings. As the debt issuance refinanced short-term debt, the short-term debt was classified as Long-Term Debt on NU's balance sheet as of September 30, 2014.	'
The Connecticut Light And Power Company [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Notes Payable To Affiliated Companies	105,400,000	287,300,000
NSTAR Electric Company [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Line of Credit Facility, Remaining Borrowing Capacity	290,500,000	346,500,000
Line of Credit Facility, Amount Outstanding	159,500,000	103,500,000
WeightedAverageDiscountRatePercent	0.16%	0.13%
Notes Payable	159,500,000	103,500,000
Public Service Company Of New Hampshire [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Notes Payable To Affiliated Companies	153,300,000	86,500,000
Western Massachusetts Electric Company [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Notes Payable To Affiliated Companies	$13,200,000	$0

PENSION_BENEFITS_AND_POSTRETIR1

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSIONS (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	$787,550,000	'	$787,550,000	'	$896,844,000
Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	19,100,000	25,600,000	60,700,000	76,700,000	'
Defined Benefit Plan Interest Cost	56,400,000	51,700,000	169,500,000	155,000,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-77,700,000	-69,500,000	-233,100,000	-208,500,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	31,700,000	52,400,000	96,500,000	158,100,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	1,100,000	1,100,000	3,300,000	3,000,000	'
Defined Benefit Plan Net Periodic Benefit Cost	30,600,000	61,300,000	96,900,000	184,300,000	'
Amount Capitalized Defined Benefit Expense	8,300,000	18,300,000	26,700,000	54,900,000	'
PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	3,100,000	4,200,000	9,300,000	12,600,000	'
Defined Benefit Plan Interest Cost	12,400,000	11,800,000	37,100,000	35,400,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-15,800,000	-13,900,000	-47,400,000	-41,600,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	3,000,000	6,500,000	9,100,000	19,500,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	-700,000	-500,000	-2,100,000	-1,500,000	'
Defined Benefit Plan Net Periodic Benefit Cost	2,000,000	8,100,000	6,000,000	24,400,000	'
Amount Capitalized Defined Benefit Expense	1,100,000	2,600,000	1,900,000	7,600,000	'
The Connecticut Light And Power Company [Member]	'	'	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	63,756,000	'	63,756,000	'	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	15,200,000	18,700,000	'
Defined Benefit Plan Interest Cost	12,500,000	12,100,000	38,100,000	36,300,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-18,700,000	-18,400,000	-56,700,000	-55,400,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	8,200,000	13,900,000	25,500,000	42,000,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	400,000	400,000	1,400,000	1,400,000	'
Defined Benefit Plan Net Periodic Benefit Cost	7,400,000	14,300,000	23,500,000	43,000,000	'
Related Intercompany Allocationsof Defined Benefit Expense	6,500,000	11,400,000	20,800,000	33,600,000	'
Amount Capitalized Defined Benefit Expense	4,300,000	7,000,000	13,600,000	21,000,000	'
The Connecticut Light And Power Company [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	600,000	900,000	1,700,000	2,600,000	'
Defined Benefit Plan Interest Cost	2,000,000	2,000,000	6,000,000	5,900,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-2,600,000	-2,500,000	-7,900,000	-7,600,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	1,000,000	1,800,000	3,200,000	5,600,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	'	'	0	'	'
Defined Benefit Plan Net Periodic Benefit Cost	1,000,000	2,200,000	3,000,000	6,500,000	'
Related Intercompany Allocationsof Defined Benefit Expense	900,000	1,700,000	3,100,000	5,300,000	'
Amount Capitalized Defined Benefit Expense	500,000	1,300,000	1,500,000	3,700,000	'
NSTAR Electric Company [Member]	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Net Periodic Benefit Cost	'	1,200,000	'	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Accrued Pension, PBOP and SERP	142,249,000	'	142,249,000	'	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	8,300,000	10,600,000	24,800,000	'
Defined Benefit Plan Interest Cost	10,300,000	14,500,000	31,000,000	43,500,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-15,700,000	-21,100,000	-47,300,000	-63,300,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	5,900,000	14,400,000	17,600,000	43,600,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	0	0	0	-200,000	'
Defined Benefit Plan Net Periodic Benefit Cost	3,500,000	16,100,000	11,900,000	48,400,000	'
Related Intercompany Allocationsof Defined Benefit Expense	2,900,000	-2,100,000	6,700,000	-6,200,000	'
Amount Capitalized Defined Benefit Expense	2,600,000	9,800,000	5,500,000	21,600,000	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Defined Benefit Plan, Funded Status of Plan	'	83,400,000	'	83,400,000	118,000,000
NSTAR Electric Company [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	800,000	'	2,300,000	'	'
Defined Benefit Plan Interest Cost	4,900,000	'	14,600,000	'	'
Defined Benefit Plan, Expected Return on Plan Assets	-6,500,000	'	-19,500,000	'	'
Defined Benefit Plan, Amortization of Gains (Losses)	-100,000	'	-400,000	'	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	-500,000	'	-1,400,000	'	'
Defined Benefit Plan Net Periodic Benefit Cost	-1,400,000	1,200,000	-4,400,000	3,500,000	'
Related Intercompany Allocationsof Defined Benefit Expense	300,000	'	400,000	'	'
Amount Capitalized Defined Benefit Expense	-500,000	'	-1,500,000	'	'
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]	'	'	'	'	'
Defined Benefit Plan, Funded Status of Plan	55,600,000	'	55,600,000	'	'
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] | Pension Plans Defined Benefit Member	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	2,300,000	3,300,000	7,400,000	9,800,000	'
Defined Benefit Plan Interest Cost	5,700,000	5,800,000	18,000,000	17,800,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-9,300,000	-9,200,000	-28,800,000	-26,200,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	2,800,000	5,400,000	8,900,000	16,200,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	100,000	100,000	500,000	400,000	'
Defined Benefit Plan Net Periodic Benefit Cost	1,600,000	5,400,000	6,000,000	18,000,000	'
Related Intercompany Allocationsof Defined Benefit Expense	1,800,000	2,600,000	6,000,000	7,800,000	'
Amount Capitalized Defined Benefit Expense	700,000	1,700,000	2,400,000	5,600,000	'
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	1,000,000	1,700,000	'
Defined Benefit Plan Interest Cost	1,100,000	1,000,000	3,200,000	3,100,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-1,400,000	-1,300,000	-4,100,000	-3,900,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	600,000	900,000	1,700,000	2,700,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	'	'	0	'	'
Defined Benefit Plan Net Periodic Benefit Cost	600,000	1,200,000	1,800,000	3,600,000	'
Related Intercompany Allocationsof Defined Benefit Expense	200,000	400,000	800,000	1,200,000	'
Amount Capitalized Defined Benefit Expense	200,000	400,000	600,000	1,100,000	'
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	2,700,000	3,500,000	'
Defined Benefit Plan Interest Cost	2,500,000	2,500,000	7,800,000	7,500,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-4,400,000	-4,300,000	-13,500,000	-13,000,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	1,700,000	2,900,000	5,200,000	8,900,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	100,000	100,000	300,000	300,000	'
Defined Benefit Plan Net Periodic Benefit Cost	700,000	2,400,000	2,500,000	7,200,000	'
Related Intercompany Allocationsof Defined Benefit Expense	1,200,000	2,000,000	3,900,000	6,000,000	'
Amount Capitalized Defined Benefit Expense	600,000	1,300,000	2,000,000	3,900,000	'
Western Massachusetts Electric Company [Member] | PBOP Plan	'	'	'	'	'
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]	'	'	'	'	'
Defined Benefit Plan Service Cost	100,000	200,000	300,000	500,000	'
Defined Benefit Plan Interest Cost	400,000	400,000	1,300,000	1,300,000	'
Defined Benefit Plan, Expected Return on Plan Assets	-600,000	-600,000	-1,700,000	-1,700,000	'
Defined Benefit Plan, Amortization of Gains (Losses)	100,000	300,000	300,000	800,000	'
Defined Benefit Plan Amortization Of Prior Service Cost Credit	'	'	0	'	'
Defined Benefit Plan Net Periodic Benefit Cost	0	300,000	200,000	900,000	'
Related Intercompany Allocationsof Defined Benefit Expense	200,000	300,000	600,000	1,000,000	'
Amount Capitalized Defined Benefit Expense	$0	$300,000	$100,000	$700,000	'

INCOME_TAXES_Details

INCOME TAXES (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]	'	'	'	'
Total Deferred Income Taxes	'	'	$64,755	$334,225
Income Tax Expense	126,539	109,351	345,858	325,442
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'	'
Income Before Income Tax Expense	363,032	320,731	949,434	939,855
Income Tax Expense	126,539	109,351	345,858	325,442
The Connecticut Light And Power Company [Member]	'	'	'	'
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]	'	'	'	'
Total Deferred Income Taxes	'	'	-14,400	89,084
Income Tax Expense	30,038	36,136	95,980	113,149
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'	'
Income Before Income Tax Expense	113,914	102,459	296,540	332,337
Income Tax Expense	30,038	36,136	95,980	113,149
Other Tax Disclosures [Abstract]	'	'	'	'
Other Information Pertaining To Income Taxes	'	'	'In the third quarter of 2014, the Company recorded a reduction to its state credit carryforwards of $11 million (CL&P $10.1 million), net of tax, as a result of an update to reflect the amounts expired. Further, the Company decreased its valuation allowance reserve for state credits by $22.3 million (all at CL&P), net of tax, to reflect the expiration of state credits in its recently filed return and the latest available data. These updates resulted in a net reduction in income tax expense of $11.3 million (CL&P $12.2 million).	'
NSTAR Electric Company [Member]	'	'	'	'
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]	'	'	'	'
Total Deferred Income Taxes	'	'	-39,399	26,358
Income Tax Expense	76,975	68,558	156,655	137,499
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'	'
Income Before Income Tax Expense	192,549	175,567	390,446	350,661
Income Tax Expense	76,975	68,558	156,655	137,499
Public Service Company Of New Hampshire [Member]	'	'	'	'
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]	'	'	'	'
Total Deferred Income Taxes	'	'	67,827	57,066
Income Tax Expense	17,603	18,196	52,199	52,797
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'	'
Income Before Income Tax Expense	45,839	46,549	137,154	137,340
Income Tax Expense	17,603	18,196	52,199	52,797
Western Massachusetts Electric Company [Member]	'	'	'	'
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]	'	'	'	'
Total Deferred Income Taxes	'	'	13,479	79,401
Income Tax Expense	10,490	8,588	26,596	30,424
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'	'
Income Before Income Tax Expense	25,155	23,613	66,381	80,465
Income Tax Expense	$10,490	$8,588	$26,596	$30,424

Environmental_Matters_Details

Environmental Matters (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Site Contingency [Line Items]	'	'
Environmental Site Quantity	65	68
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	$35.40	'
Ending Balance	34.7	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	16	18
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	3.4	'
Ending Balance	4	3.4
NSTAR Electric Company [Member]	'	'
Site Contingency [Line Items]	'	'
Environmental Site Quantity	13	12
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	1.2	'
Ending Balance	1.1	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	4	5
Accrual for Environmental Loss Contingencies [Roll Forward]	'	'
Beginning Balance	0.4	'
Ending Balance	$0.50	$0.40

LongTerm_Contractual_Arrangeme1

Long-Term Contractual Arrangements (Details) (Renewable Energy Contracts [Member], USD $)	Sep. 30, 2014
In Millions, unless otherwise specified
The Connecticut Light And Power Company [Member]	'
Long-term Purchase Commitment [Line Items]	'
Unrecorded Unconditional Purchase Obligation, Due within One Year	$20
Unrecorded Unconditional Purchase Obligation, Due within Two Years	60.7
Unrecorded Unconditional Purchase Obligation, Due within Three Years	66.1
Unrecorded Unconditional Purchase Obligation, Due within Four Years	67
Unrecorded Unconditional Purchase Obligation, Due within Five Years	67.7
Unrecorded Unconditional Purchase Obligation, Due after Five Years	717
Unrecorded Unconditional Purchase Obligation, Total	998.5
NSTAR Electric Company [Member]	'
Long-term Purchase Commitment [Line Items]	'
Unrecorded Unconditional Purchase Obligation, Due within One Year	21.8
Unrecorded Unconditional Purchase Obligation, Due within Two Years	86.3
Unrecorded Unconditional Purchase Obligation, Due within Three Years	100
Unrecorded Unconditional Purchase Obligation, Due within Four Years	96.1
Unrecorded Unconditional Purchase Obligation, Due within Five Years	59.6
Unrecorded Unconditional Purchase Obligation, Due after Five Years	377.6
Unrecorded Unconditional Purchase Obligation, Total	741.4
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

Contractual_Obligations_with_Y

Contractual Obligations with Yankee Companies (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
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
Court Of Federal Claims Ruling To MYAPC	'	'	35.8
Connecticut Yankee Proceeds Received	90	36.3	'
Yankee Atomic Proceeds Received	73.3	'	'
Maine Yankee Proceeds Received	$35.80	'	'
Refund Obligation To Customers	'As of September 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. Refunds to customers for these DOE proceeds began in the third quarter of 2014. For further information, see Note 2, "Regulatory Accounting," to the financial statements.	'	'
MYAPC Phase One Damages Proceeds To Member Companies	'DOE Phase I Damages - Proceeds Received – On September 17, 2014, in accordance with the MYAPC refund plan, MYAPC returned a portion of the DOE Phase I Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, in the amount of $3.2 million, $1.1 million, $1.4 million and $0.8 million, respectively. These amounts reduced receivables at CL&P, NSTAR Electric, PSNH and WMECO.	'	'

Guarantees_and_Indemnification1

Guarantees and Indemnifications (Details) (USD $)	Sep. 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	64.3
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	15.3
Guarantee Of Debt Of Ne Hydros [Member]	'
Guarantee Obligations [Line Items]	'
Guarantee Obligations Maximum Exposure	$2

Other_Contingencies_Details

Other Contingencies (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2013
In Millions, unless otherwise specified
FERC ROE Reserve - First Complaint - Base ROE [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	$24.90	$1.20	$23.70
FERC ROE Reserve - First Complaint - Base ROE [Member] | The Connecticut Light And Power Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	13.3	0.5	12.8
FERC ROE Reserve - First Complaint - Base ROE [Member] | NSTAR Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	6.1	0.4	5.7
FERC ROE Reserve - First Complaint - Base ROE [Member] | Public Service Company Of New Hampshire [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	2.4	0.1	2.3
FERC ROE Reserve - First Complaint - Base ROE [Member] | Western Massachusetts Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	3.1	0.2	2.9
FERC ROE Reserve - Second Complaint - Base ROE [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	27.4	27.4	'
FERC ROE Reserve - Second Complaint - Base ROE [Member] | The Connecticut Light And Power Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	13.5	13.5	'
FERC ROE Reserve - Second Complaint - Base ROE [Member] | NSTAR Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	7.5	7.5	'
FERC ROE Reserve - Second Complaint - Base ROE [Member] | Public Service Company Of New Hampshire [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	2.7	2.7	'
FERC ROE Reserve - Second Complaint - Base ROE [Member] | Western Massachusetts Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	3.7	3.7	'
FERC ROE Reserve - Incentive - First and Second Complaint [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	23.8	23.8	'
FERC ROE Reserve - Incentive - First and Second Complaint [Member] | The Connecticut Light And Power Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	16.1	16.1	'
FERC ROE Reserve - Incentive - First and Second Complaint [Member] | NSTAR Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	2	2	'
FERC ROE Reserve - Incentive - First and Second Complaint [Member] | Public Service Company Of New Hampshire [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	0.8	0.8	'
FERC ROE Reserve - Incentive - First and Second Complaint [Member] | Western Massachusetts Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	4.9	4.9	'
FERC ROE Reserve - Cumulative [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	76.1	52.4	23.7
FERC ROE Reserve - Cumulative [Member] | The Connecticut Light And Power Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	42.9	30.1	12.8
FERC ROE Reserve - Cumulative [Member] | NSTAR Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	15.6	9.9	5.7
FERC ROE Reserve - Cumulative [Member] | Public Service Company Of New Hampshire [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	5.9	3.6	2.3
FERC ROE Reserve - Cumulative [Member] | Western Massachusetts Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	11.7	8.8	2.9
FERC ROE Reserve - Cumulative - After Tax Charge [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	'	32.1	14.3
FERC ROE Reserve - Cumulative - After Tax Charge [Member] | The Connecticut Light And Power Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	'	18.5	7.7
FERC ROE Reserve - Cumulative - After Tax Charge [Member] | NSTAR Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	'	6.1	3.4
FERC ROE Reserve - Cumulative - After Tax Charge [Member] | Public Service Company Of New Hampshire [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	'	2	1.4
FERC ROE Reserve - Cumulative - After Tax Charge [Member] | Western Massachusetts Electric Company [Member]	'	'	'
Loss Contingencies Line Items	'	'	'
Loss Contingency Estimate Of Possible Loss	'	$5.50	$1.80

FAIR_VALUE_OF_FINANCIAL_INSTRU2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) (USD $)	Sep. 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	8,412,600,000	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	151,000,000	152,700,000
Other Long Term Debt	8,876,300,000	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	2,841,800,000	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	110,100,000	110,500,000
Other Long Term Debt	3,189,500,000	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	40,900,000	42,200,000
Other Long Term Debt	1,959,400,000	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	999,200,000	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	1,046,400,000	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	628,700,000	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	$667,400,000	$640,100,000

ACCUMULATED_OTHER_COMPREHENSIV2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	($46,031,000)	($72,900,000)
Other Comprehensive Income Before Reclassifications, Net of Tax	'	'	1,400,000	-800,000
Reclassification From OCI, Net Of Tax	'	'	4,400,000	6,300,000
Other Comprehensive Income (Loss), Net of Tax, Total	1,335,000	2,082,000	5,859,000	5,467,000
AOCI Ending Balance	-40,172,000	-67,400,000	-40,172,000	-67,400,000
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
Total Interest Expense	-89,738,000	-87,476,000	-272,208,000	-250,583,000
Income Tax Expense	-126,539,000	-109,351,000	-345,858,000	-325,442,000
Net Income Attributable to Controlling Interests	234,614,000	209,501,000	597,937,000	608,610,000
The Connecticut Light And Power Company [Member]	'	'	'	'
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-1,387,000	'
Other Comprehensive Income (Loss), Net of Tax, Total	104,000	110,000	341,000	306,000
AOCI Ending Balance	-1,046,000	'	-1,046,000	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
Total Interest Expense	-38,735,000	-35,284,000	-110,448,000	-98,964,000
Income Tax Expense	-30,038,000	-36,136,000	-95,980,000	-113,149,000
Public Service Company Of New Hampshire [Member]	'	'	'	'
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-8,550,000	'
Other Comprehensive Income (Loss), Net of Tax, Total	277,000	288,000	885,000	822,000
AOCI Ending Balance	-7,665,000	'	-7,665,000	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
Total Interest Expense	-11,024,000	-10,866,000	-33,995,000	-34,181,000
Income Tax Expense	-17,603,000	-18,196,000	-52,199,000	-52,797,000
Western Massachusetts Electric Company [Member]	'	'	'	'
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-3,517,000	'
Other Comprehensive Income (Loss), Net of Tax, Total	83,000	85,000	256,000	246,000
AOCI Ending Balance	-3,261,000	'	-3,261,000	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
Total Interest Expense	-6,576,000	-6,231,000	-18,929,000	-18,800,000
Income Tax Expense	-10,490,000	-8,588,000	-26,596,000	-30,424,000
Qualified Cash Flow Hedging Instruments [Member]	'	'	'	'
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-14,400,000	-16,400,000
Reclassification From OCI, Net Of Tax	'	'	1,500,000	1,500,000
Other Comprehensive Income (Loss), Net of Tax, Total	'	'	1,500,000	1,500,000
AOCI Ending Balance	-12,900,000	-14,900,000	-12,900,000	-14,900,000
Unrealized Gains Losses on Available for Sale Securities [Member]	'	'	'	'
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	400,000	1,300,000
Other Comprehensive Income Before Reclassifications, Net of Tax	'	'	200,000	-800,000
Other Comprehensive Income (Loss), Net of Tax, Total	'	'	200,000	-800,000
AOCI Ending Balance	600,000	500,000	600,000	500,000
Pension, SERP and PBOP Benefit Plans [Member]	'	'	'	'
Accumulated Other Comprehensive Income Loss Net Of Tax RollForward [Abstract]	'	'	'	'
AOCI Beginning Balance	'	'	-32,000,000	-57,800,000
Other Comprehensive Income Before Reclassifications, Net of Tax	'	'	1,200,000	'
Reclassification From OCI, Net Of Tax	'	'	2,900,000	4,800,000
Other Comprehensive Income (Loss), Net of Tax, Total	'	'	4,100,000	4,800,000
AOCI Ending Balance	-27,900,000	-53,000,000	-27,900,000	-53,000,000
Reclassification out of Accumulated Other Comprehensive Income [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
Net Income Attributable to Controlling Interests	-1,500,000	-2,100,000	-4,400,000	-6,300,000
Reclassification out of Accumulated Other Comprehensive Income [Member] | Qualified Cash Flow Hedging Instruments [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
Total Interest Expense	-800,000	-800,000	-2,500,000	-2,500,000
Income Tax Expense	300,000	300,000	1,000,000	1,000,000
Net Income Attributable to Controlling Interests	-500,000	-500,000	-1,500,000	-1,500,000
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension, SERP and PBOP Benefit Plans [Member]	'	'	'	'
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Abstract]	'	'	'	'
OCI Reclassification Adjustment for Net Actuarial Gain (Loss), before Tax	-1,600,000	-2,500,000	-4,700,000	-7,300,000
OCI Reclassification Adjustment for Amortization of Prior Service Cost, before tax	0	0	-100,000	-100,000
OCI Reclassification Adjustment for Pension, SERP and PBOP Plans, before Tax	-1,600,000	-2,500,000	-4,800,000	-7,400,000
Income Tax Expense	600,000	900,000	1,900,000	2,600,000
Net Income Attributable to Controlling Interests	($1,000,000)	($1,600,000)	($2,900,000)	($4,800,000)

COMMON_SHARES_Details

COMMON SHARES (Details) (USD $)	Sep. 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	333,353,446	333,113,492
Treasury Stock Shares	16,730,815	17,796,672
Common Stock, Shares, Outstanding	316,622,631	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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Shareholders' Equity, Beginning Balance	'	'	$9,611,528,000	'
Net Income	236,493,000	211,380,000	603,576,000	614,413,000
Dividends on Common Shares	'	'	0	'
Issuance of Common Shares	'	'	0	'
Other Transcations, Net	0	'	0	'
Net Income Attributable to Noncontrolling Interests	1,879,000	1,879,000	5,639,000	5,803,000
Other Comprehensive Income (Loss), Net of Tax	1,335,000	2,082,000	5,859,000	5,467,000
Shareholders' Equity, Ending Balance	9,890,552,000	'	9,890,552,000	'
Common Shareholders Equity [Member]	'	'	'	'
Shareholders' Equity, Beginning Balance	9,753,800,000	9,406,600,000	9,611,500,000	9,237,100,000
Net Income	236,500,000	211,400,000	603,600,000	614,400,000
Dividends on Common Shares	-124,200,000	-114,900,000	-372,200,000	-346,900,000
Dividends on Preferred Stock	-1,900,000	-1,900,000	-5,600,000	-5,800,000
Issuance of Common Shares	1,000,000	1,400,000	6,400,000	10,200,000
Other Transcations, Net	24,100,000	12,800,000	41,000,000	3,000,000
Net Income Attributable to Noncontrolling Interests	'	'	0	0
Other Comprehensive Income (Loss), Net of Tax	1,300,000	2,100,000	5,900,000	5,500,000
Shareholders' Equity, Ending Balance	9,890,600,000	9,517,500,000	9,890,600,000	9,517,500,000
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 on Preferred Stock	-1,900,000	-1,900,000	-5,600,000	-5,800,000
Net Income Attributable to Noncontrolling Interests	1,900,000	1,900,000	5,600,000	5,800,000
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		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Notes To Consolidated Financial Statements [Abstract]	'	'	'	'
Net Income Attributable to Controlling Interests	$234,614	$209,501	$597,937	$608,610
Basic	316,340,691	315,291,346	315,941,904	315,191,752
Weighted Average Number Diluted Shares Outstanding Adjustment	1,214,234	926,893	1,244,586	869,379
Diluted	317,554,925	316,218,239	317,186,490	316,061,131
Earnings Per Share Basic And Diluted	$0.74	$0.66	$1.89	$1.93
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	0	0	0	2,100

SEGMENT_INFORMATION_Details

SEGMENT INFORMATION (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	$1,892,532,000	$1,892,590,000	$5,860,736,000	$5,523,475,000	'
Operating Income	440,910,000	399,262,000	1,202,588,000	1,168,783,000	'
Total Interest Expense	-89,738,000	-87,476,000	-272,208,000	-250,583,000	'
Other Income/(Loss), Net	11,860,000	8,945,000	19,054,000	21,655,000	'
Income Tax Expense	-126,539,000	-109,351,000	-345,858,000	-325,442,000	'
Net Income	236,493,000	211,380,000	603,576,000	614,413,000	'
Net Income Attributable to Noncontrolling Interests	-1,879,000	-1,879,000	-5,639,000	-5,803,000	'
Net Income Attributable to Controlling Interests	234,614,000	209,501,000	597,937,000	608,610,000	'
Total Assets	27,982,311,000	'	27,982,311,000	'	27,795,537,000
Investments in Property, Plant and Equipment	'	'	1,117,493,000	1,073,759,000	'
Electric Distribution Member	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	1,502,600,000	1,508,600,000	4,350,400,000	4,104,400,000	'
Depreciation And Amortization	-71,700,000	-159,600,000	-309,900,000	-488,700,000	'
Operating Expenses, Other	-1,141,500,000	-1,064,100,000	-3,343,900,000	-2,952,400,000	'
Operating Income	289,400,000	284,900,000	696,600,000	663,300,000	'
Total Interest Expense	-49,200,000	-44,300,000	-143,800,000	-129,900,000	'
Other Income/(Loss), Net	9,300,000	5,500,000	13,600,000	12,600,000	'
Net Income Attributable to Controlling Interests	153,400,000	156,900,000	349,100,000	347,500,000	'
Total Assets	16,702,300,000	'	16,702,300,000	'	17,260,000,000
Investments in Property, Plant and Equipment	'	'	480,100,000	501,900,000	'
Natural Gas Distribution [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	109,200,000	97,100,000	737,500,000	613,000,000	'
Depreciation And Amortization	-16,400,000	-16,400,000	-51,100,000	-50,500,000	'
Operating Expenses, Other	-98,400,000	-89,400,000	-586,200,000	-483,600,000	'
Operating Income	-5,600,000	-8,700,000	100,200,000	78,900,000	'
Total Interest Expense	-8,500,000	-8,600,000	-25,600,000	-24,800,000	'
Other Income/(Loss), Net	100,000	500,000	200,000	700,000	'
Net Income Attributable to Controlling Interests	-9,900,000	-10,400,000	44,200,000	34,100,000	'
Total Assets	2,801,100,000	'	2,801,100,000	'	2,759,700,000
Investments in Property, Plant and Equipment	'	'	120,600,000	91,200,000	'
Transmission [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	262,500,000	234,100,000	721,400,000	721,500,000	'
Depreciation And Amortization	-37,400,000	-34,500,000	-111,400,000	-100,900,000	'
Operating Expenses, Other	-74,200,000	-73,400,000	-211,500,000	-199,100,000	'
Operating Income	150,900,000	126,200,000	398,500,000	421,500,000	'
Total Interest Expense	-24,500,000	-26,600,000	-78,800,000	-73,700,000	'
Other Income/(Loss), Net	2,700,000	2,900,000	6,900,000	8,500,000	'
Net Income Attributable to Controlling Interests	88,100,000	58,600,000	206,800,000	215,400,000	'
Total Assets	7,404,500,000	'	7,404,500,000	'	6,745,800,000
Investments in Property, Plant and Equipment	'	'	469,900,000	458,200,000	'
Other Segment [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	211,200,000	212,500,000	568,100,000	650,400,000	'
Depreciation And Amortization	-13,800,000	-11,200,000	-28,300,000	-52,000,000	'
Operating Expenses, Other	-192,400,000	-206,800,000	-534,100,000	-599,000,000	'
Operating Income	5,000,000	-5,500,000	5,700,000	-600,000	'
Total Interest Expense	-8,600,000	-9,200,000	-27,200,000	-26,300,000	'
Other Income/(Loss), Net	226,400,000	312,100,000	657,900,000	866,200,000	'
Net Income Attributable to Controlling Interests	228,300,000	313,100,000	653,400,000	868,700,000	'
Total Assets	12,270,200,000	'	12,270,200,000	'	11,842,400,000
Investments in Property, Plant and Equipment	'	'	46,900,000	22,500,000	'
Eliminations Segment [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	-193,000,000	-159,700,000	-516,700,000	-565,800,000	'
Depreciation And Amortization	8,600,000	2,600,000	12,700,000	7,200,000	'
Operating Expenses, Other	185,600,000	159,500,000	505,600,000	564,300,000	'
Operating Income	1,200,000	2,400,000	1,600,000	5,700,000	'
Total Interest Expense	1,000,000	1,200,000	3,200,000	4,100,000	'
Other Income/(Loss), Net	-226,600,000	-312,100,000	-659,500,000	-866,300,000	'
Net Income Attributable to Controlling Interests	-225,300,000	-308,700,000	-655,600,000	-857,100,000	'
Total Assets	-11,195,800,000	'	-11,195,800,000	'	-10,812,400,000
Investments in Property, Plant and Equipment	'	'	0	0	'
Total [Member]	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'
Operating Revenues	1,892,500,000	1,892,600,000	5,860,700,000	5,523,500,000	'
Depreciation And Amortization	-130,700,000	-219,100,000	-488,000,000	-684,900,000	'
Operating Expenses, Other	-1,320,900,000	-1,274,200,000	-4,170,100,000	-3,669,800,000	'
Operating Income	440,900,000	399,300,000	1,202,600,000	1,168,800,000	'
Total Interest Expense	-89,800,000	-87,500,000	-272,200,000	-250,600,000	'
Other Income/(Loss), Net	11,900,000	8,900,000	19,100,000	21,700,000	'
Net Income Attributable to Controlling Interests	234,600,000	209,500,000	597,900,000	608,600,000	'
Total Assets	27,982,300,000	'	27,982,300,000	'	27,795,500,000
Investments in Property, Plant and Equipment	'	'	$1,117,500,000	$1,073,800,000	'