CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current Assets:
Cash	$ 43,364	$ 45,748
Receivables, Net	765,391	792,822
Unbilled Revenues	224,982	216,040
Fuel, Materials and Supplies	303,233	267,713
Regulatory Assets Current	535,791	705,025
Prepayments and Other Current Assets	214,288	199,947
Total Current Assets	2,087,049	2,227,295
Property, Plant and Equipment, Net	17,576,186	16,605,010
Deferred Debits and Other Assets:
Regulatory Assets Long Term	3,758,694	5,132,411
Goodwill	3,519,401	3,519,401
Marketable Securities	488,515	400,329
Derivative Assets Noncurrent	74,155	90,612
Other Long-Term Assets	291,537	327,766
Total Deferred Debits and Other Assets	8,132,302	9,470,519
Total Assets	27,795,537	28,302,824
Current Liabilities:
Notes Payable to Banks	1,093,000	1,120,196
Long-Term Debt - Current Portion	533,346	763,338
Accounts Payable - Current	742,251	764,350
Regulatory Liability Current	204,278	134,115
Other Liabilities - Current	702,776	861,691
Total Current Liabilities	3,275,651	3,643,690
Rate Reduction Bonds	0	82,139
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	4,029,026	3,463,347
Regulatory Liabilities Long-Term	502,984	540,162
Long-Term Derivative Liabilities	624,050	882,654
Accrued Pension, PBOP and SERP	896,844	2,130,497
Other Long-Term Liabilities	923,053	967,561
Total Deferred Credits and Other Liabilities	6,975,957	7,984,221
Capitalization:
Long-Term Debt	7,776,833	7,200,156
Noncontrolling Interest in Consolidated Subsidiary:
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	155,568	155,568
Common Shareholders' Equity:
Common Stock	1,665,351	1,662,547
Capital Surplus, Paid In	6,192,765	6,183,267
Retained Earnings	2,125,980	1,802,714
Accumulated Other Comprehensive Loss	(46,031)	(72,854)
Treasury Stock	(326,537)	(338,624)
Common Shareholders' Equity	9,611,528	9,237,050
Total Capitalization	17,543,929	16,592,774
Total Liabilities and Capitalization	27,795,537	28,302,824
The Connecticut Light And Power Company [Member]
Current Assets:
Cash	7,237	1
Receivables, Net	319,670	284,787
Accounts Receivable from Affiliated Companies	13,777	6,641
Unbilled Revenues	92,401	85,353
Regulatory Assets Current	150,943	185,858
Materials and Supplies	54,606	64,603
Prepayments and Other Current Assets	53,082	26,413
Total Current Assets	691,716	653,656
Property, Plant and Equipment, Net	6,451,259	6,152,959
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,663,147	2,158,363
Derivative Assets Noncurrent	71,384	90,612
Other Long-Term Assets	102,996	86,498
Total Deferred Debits and Other Assets	1,837,527	2,335,473
Total Assets	8,980,502	9,142,088
Current Liabilities:
Notes Payable To Affiliated Companies	287,300	99,296
Long-Term Debt - Current Portion	150,000	125,000
Accounts Payable - Current	201,047	262,857
Accounts Payable to Affiliated Companies	56,531	52,326
Obligations to Third Party Suppliers	73,914	67,344
Accrued Taxes	37,186	60,109
Regulatory Liability Current	93,961	32,119
Derivative Liabilities - Current	92,233	96,931
Other Liabilities - Current	97,530	125,662
Total Current Liabilities	1,089,702	921,644
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,510,586	1,336,105
Regulatory Liabilities Long-Term	93,757	124,319
Long-Term Derivative Liabilities	617,072	865,571
Accrued Pension, PBOP and SERP	95,895	304,696
Other Long-Term Liabilities	163,588	197,434
Total Deferred Credits and Other Liabilities	2,480,898	2,828,125
Capitalization:
Long-Term Debt	2,591,208	2,737,790
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	1,682,047	1,640,149
Retained Earnings	961,482	839,628
Accumulated Other Comprehensive Loss	(1,387)	(1,800)
Common Shareholders' Equity	2,702,494	2,538,329
Total Capitalization	5,409,902	5,392,319
Total Liabilities and Capitalization	8,980,502	9,142,088
NSTAR Electric Company [Member]
Current Assets:
Cash	8,021	13,695
Receivables, Net	209,711	202,025
Accounts Receivable from Affiliated Companies	27,264	160,176
Unbilled Revenues	41,368	41,377
Regulatory Assets Current	204,144	347,081
Materials and Supplies	44,236	26,754
Prepayments and Other Current Assets	36,710	1,332
Total Current Assets	571,454	792,440
Property, Plant and Equipment, Net	5,043,887	4,735,297
Deferred Debits and Other Assets:
Regulatory Assets Long Term	1,235,156	1,444,870
Other Long-Term Assets	60,624	87,382
Total Deferred Debits and Other Assets	1,295,780	1,532,252
Total Assets	6,911,121	7,059,989
Current Liabilities:
Notes Payable to Banks	103,500	276,000
Long-Term Debt - Current Portion	301,650	1,650
Accounts Payable - Current	207,559	168,611
Accounts Payable to Affiliated Companies	75,707	247,061
Deferred Tax Liabilities Current	50,128	104,668
Regulatory Liability Current	53,958	47,539
Other Liabilities - Current	118,410	144,433
Total Current Liabilities	910,912	989,962
Rate Reduction Bonds	0	43,493
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,466,835	1,321,026
Regulatory Liabilities Long-Term	253,108	244,224
Accrued Pension, PBOP and SERP	118,010	360,932
Other Long-Term Liabilities	142,214	183,190
DueToRelatedPartiesNoncurrent	64,172	70,221
Total Deferred Credits and Other Liabilities	2,044,339	2,179,593
Capitalization:
Long-Term Debt	1,499,417	1,600,911
Noncontrolling Interest in Consolidated Subsidiary:
Temporary Equity, Carrying Amount, Attributable to Noncontrolling Interest	43,000	43,000
Common Shareholders' Equity:
Common Stock	0	0
Capital Surplus, Paid In	992,625	992,625
Retained Earnings	1,420,828	1,210,405
Common Shareholders' Equity	2,413,453	2,203,030
Total Capitalization	3,955,870	3,846,941
Total Liabilities and Capitalization	6,911,121	7,059,989
Public Service Company Of New Hampshire [Member]
Current Assets:
Cash	130	2,493
Receivables, Net	76,331	87,164
Accounts Receivable from Affiliated Companies	90	723
Unbilled Revenues	38,344	39,982
Taxes Receivable	2,180	17,177
Fuel, Materials and Supplies	128,736	95,345
Regulatory Assets Current	92,194	62,882
Prepayments and Other Current Assets	21,920	22,205
Total Current Assets	359,925	327,971
Property, Plant and Equipment, Net	2,467,556	2,352,515
Deferred Debits and Other Assets:
Regulatory Assets Long Term	219,346	351,059
Other Long-Term Assets	39,891	83,052
Total Deferred Debits and Other Assets	259,237	434,111
Total Assets	3,086,718	3,114,597
Current Liabilities:
Notes Payable To Affiliated Companies	86,500	63,300
Long-Term Debt - Current Portion	50,000
Accounts Payable - Current	82,920	62,864
Accounts Payable to Affiliated Companies	22,040	21,337
Deferred Tax Liabilities Current	28,596	10,364
Regulatory Liability Current	20,643	23,002
Other Liabilities - Current	42,811	40,586
Renewable Portfolio Standards Compliance Obligation	8,918	17,383
Total Current Liabilities	342,428	238,836
Rate Reduction Bonds	0	29,294
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	500,166	441,577
Regulatory Liabilities Long-Term	51,723	52,418
Accrued Pension, PBOP and SERP	15,272	33,981
Other Long-Term Liabilities	46,247	47,896
Total Deferred Credits and Other Liabilities	613,408	762,020
DefinedBenefitPensionPlanLiabilitiesNoncurrent		186,148
Capitalization:
Long-Term Debt	999,006	997,932
Common Shareholders' Equity:
Common Stock	0	0
Capital Surplus, Paid In	701,911	701,052
Retained Earnings	438,515	395,118
Accumulated Other Comprehensive Loss	(8,550)	(9,655)
Common Shareholders' Equity	1,131,876	1,086,515
Total Capitalization	2,130,882	2,084,447
Total Liabilities and Capitalization	3,086,718	3,114,597
Western Massachusetts Electric Company [Member]
Current Assets:
Cash	0	1
Receivables, Net	49,018	47,297
Accounts Receivable from Affiliated Companies	47,607	164
Unbilled Revenues	16,562	16,192
Taxes Receivable	432	15,513
Regulatory Assets Current	43,024	42,370
Marketable Securities - Current	26,628	27,352
Prepayments and Other Current Assets	10,479	7,963
Total Current Assets	193,750	156,852
Property, Plant and Equipment, Net	1,381,060	1,290,498
Deferred Debits and Other Assets:
Regulatory Assets Long Term	146,088	221,752
Marketable Securities	31,243	30,342
Other Long-Term Assets	40,679	23,625
Total Deferred Debits and Other Assets	218,010	275,719
Total Assets	1,792,820	1,723,069
Current Liabilities:
Notes Payable To Affiliated Companies	0	31,900
Long-Term Debt - Current Portion	0	55,000
Accounts Payable - Current	62,961	68,141
Accounts Payable to Affiliated Companies	9,230	7,103
Accrued Interest	7,525	8,304
Deferred Tax Liabilities Current	13,098	8,404
Regulatory Liability Current	19,858	21,037
Other Liabilities - Current	20,629	15,754
CounterPartyDeposit	7,688	751
Total Current Liabilities	140,989	216,394
Rate Reduction Bonds	0	9,352
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	396,933	303,111
Regulatory Liabilities Long-Term	13,873	9,686
Accrued Pension, PBOP and SERP	3,911	11,884
Other Long-Term Liabilities	28,619	40,148
Total Deferred Credits and Other Liabilities	443,336	389,044
DefinedBenefitPensionPlanLiabilitiesNoncurrent		24,215
Capitalization:
Long-Term Debt	629,389	550,270
Common Shareholders' Equity:
Common Stock	10,866	10,866
Capital Surplus, Paid In	390,743	390,412
Retained Earnings	181,014	160,577
Accumulated Other Comprehensive Loss	(3,517)	(3,846)
Common Shareholders' Equity	579,106	558,009
Total Capitalization	1,208,495	1,108,279
Total Liabilities and Capitalization	$ 1,792,820	$ 1,723,069