CONSOLIDATED STATEMENT OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating Activities:
Net Income	$ 229,968	$ 100,755
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	154,977	80,839
Deferred Income Tax Expense (Benefit)	168,938	52,474
Pension and PBOP Expense, Net of PBOP Contributions	53,102	42,268
Pension and Other Postretirement Benefit Contributions	(47,048)	(98,910)
Regulatory (Underrecoveries)/Overrecoveries, Net	39,218	(27,569)
Amortization of Regulatory Assets/(Liabilities), Net	54,049	5,426
Amortization of Rate Reduction Bonds	34,499	18,347
Other Noncash Income (Expense)	(51,106)	(5,484)
Proceeds from DOE Damages Claim	77,936
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(129,431)	29,276
Inventory	28,487	30,108
Taxes Receivable/(Accrued)	(21,295)	11,758
Change in Accounts Payable	(86,916)	(190,232)
Other Current Assets and Liabilities	(32,235)	(40,240)
Net Cash Flows Provided by Operating Activities	473,143	8,816
Investing Activities:
Investments in Property, Plant and Equipment	(388,950)	(304,294)
Proceeds from Sales of Marketable Securities	98,070	40,947
Purchases of Marketable Securities	(184,030)	(41,570)
Other Investing Activities	27,997	2,448
Net Cash Flows Used in Investing Activities	(446,913)	(302,469)
Financing Activities:
Cash Dividends on Common Stock	(116,431)	(52,104)
Cash Dividends on Preferred Stock	(1,879)	(1,390)
Increase/(Decrease) in Short-Term Debt	(228,000)	343,000
Issuance of Long-Term Debt	400,000	300,000
Retirements of Rate Reduction Bonds	(62,529)	(17,903)
Other Financing Activities	(2,322)	(1,130)
Net Cash Flows Provided by/(Used in) Financing Activities	(11,161)	570,473
Net Increase/(Decrease) in Cash	15,069	276,820
Cash - Beginning of Year	45,748	6,559
Cash - End of Year	60,817	283,379
The Connecticut Light And Power Company [Member]
Operating Activities:
Net Income	85,008	53,985
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	42,448	41,070
Deferred Income Tax Expense (Benefit)	65,475	32,460
Pension and PBOP Expense, Net of PBOP Contributions	8,183	9,095
Regulatory (Underrecoveries)/Overrecoveries, Net	(15,835)	(39,407)
Amortization of Regulatory Assets/(Liabilities), Net	10,787	7,994
Other Noncash Income (Expense)	3,653	(6,399)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(32,041)	28,685
Taxes Receivable/(Accrued)	(12,777)	16,551
Change in Accounts Payable	(106,140)	(146,676)
Other Current Assets and Liabilities	(22,340)	(44,484)
Net Cash Flows Provided by Operating Activities	26,421	(47,126)
Investing Activities:
Investments in Property, Plant and Equipment	(89,360)	(108,842)
Other Investing Activities	447	1,139
Net Cash Flows Used in Investing Activities	(88,913)	(107,703)
Financing Activities:
Cash Dividends on Common Stock	(38,000)	(33,495)
Cash Dividends on Preferred Stock	(1,390)	(1,390)
Increase/(Decrease) in Short-Term Debt	(283,700)	194,750
Issuance of Long-Term Debt	400,000
Other Financing Activities	(6,112)	(1,200)
Net Cash Flows Provided by/(Used in) Financing Activities	70,798	158,665
Net Increase/(Decrease) in Cash	8,306	3,836
Cash - Beginning of Year	1	1
Cash - End of Year	8,307	3,837
Public Service Company Of New Hampshire [Member]
Operating Activities:
Net Income	28,996	21,262
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	22,568	21,208
Deferred Income Tax Expense (Benefit)	10,143	8,908
Pension and PBOP Expense, Net of PBOP Contributions	8,022	7,032
Pension and Other Postretirement Benefit Contributions	(35,146)	(89,012)
Regulatory (Underrecoveries)/Overrecoveries, Net	(799)	911
Amortization of Regulatory Assets/(Liabilities), Net	(3,051)	(2,622)
Amortization of Rate Reduction Bonds	14,756	13,930
Other Noncash Income (Expense)	(1,505)	9,569
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(13,889)	2,480
Inventory	562	9,361
Taxes Receivable/(Accrued)	23,137	10,138
Change in Accounts Payable	31,257	(16,073)
Other Current Assets and Liabilities	22,152	18,869
Net Cash Flows Provided by Operating Activities	107,203	15,961
Investing Activities:
Investments in Property, Plant and Equipment	(64,956)	(67,059)
(Increase) Decrease In Notes Receivable From Affiliated Company	0	55,900
Other Investing Activities	(17)	963
Net Cash Flows Used in Investing Activities	(64,973)	(10,196)
Financing Activities:
Cash Dividends on Common Stock	(17,000)	(42,891)
Increase/(Decrease) in Short-Term Debt	(9,900)	52,900
Retirements of Rate Reduction Bonds	(14,320)	(13,463)
Other Financing Activities	(127)	(116)
Net Cash Flows Provided by/(Used in) Financing Activities	(41,347)	(3,570)
Net Increase/(Decrease) in Cash	883	2,195
Cash - Beginning of Year	2,493	56
Cash - End of Year	3,376	2,251
Western Massachusetts Electric Company [Member]
Operating Activities:
Net Income	18,603	14,186
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	8,970	7,697
Deferred Income Tax Expense (Benefit)	16,828	9,198
Pension and PBOP Expense, Net of PBOP Contributions	1,246	1,766
Regulatory (Underrecoveries)/Overrecoveries, Net	(2,357)	(1,778)
Amortization of Regulatory Assets/(Liabilities), Net	129	(343)
Amortization of Rate Reduction Bonds	4,689	4,418
Other Noncash Income (Expense)	(2,545)	(1,071)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(4,907)	(2,274)
Taxes Receivable/(Accrued)	21,600	1,051
Change in Accounts Payable	17,667	(21,870)
Other Current Assets and Liabilities	(8,931)	(5,885)
Net Cash Flows Provided by Operating Activities	70,992	5,095
Investing Activities:
Investments in Property, Plant and Equipment	(66,340)	(85,011)
Proceeds from Sales of Marketable Securities	21,035	31,579
Purchases of Marketable Securities	21,191	31,680
(Increase) Decrease In Notes Receivable From Affiliated Company		(11,000)
Other Investing Activities	500	(169)
Net Cash Flows Used in Investing Activities	(65,996)	(74,281)
Financing Activities:
Cash Dividends on Common Stock	(10,000)	(9,432)
Increase/(Decrease) in Notes Payable to Affiliate	11,500	83,200
Retirements of Rate Reduction Bonds	4,716,000	4,440,000
Other Financing Activities	(13)	(17)
Net Cash Flows Provided by/(Used in) Financing Activities	(3,229)	69,311
Net Increase/(Decrease) in Cash	1,767	125
Cash - Beginning of Year	1	1
Cash - End of Year	1,768	126
NSTAR Electric Company [Member]
Operating Activities:
Net Income	48,122	3,940
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Bad Debt Expense	5,523	21,618
Depreciation	45,441	42,529
Deferred Income Tax Expense (Benefit)	26,571	(19,446)
Pension and PBOP Expense, Net of PBOP Contributions	6,420	16,997
Regulatory (Underrecoveries)/Overrecoveries, Net	(2,951)	24,719
Amortization of Regulatory Assets/(Liabilities), Net	46,994	23,880
Amortization of Rate Reduction Bonds	15,054	22,581
Other Noncash Income (Expense)	(23,969)	(22,647)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(174,978)	15,109
Inventory	(7,060)	(9,340)
Taxes Receivable/(Accrued)	(22,501)	14,645
Change in Accounts Payable	107,843	(72,303)
Other Current Assets and Liabilities	18,916	34,223
Net Cash Flows Provided by Operating Activities	89,425	96,505
Investing Activities:
Investments in Property, Plant and Equipment	(107,573)	(92,870)
Decrease in Other Deposits	33,631	25,898
Other Investing Activities	(86)	375
Net Cash Flows Used in Investing Activities	(74,028)	(66,597)
Financing Activities:
Cash Dividends on Common Stock	0	(57,100)
Cash Dividends on Preferred Stock	(490)	(490)
Increase/(Decrease) in Short-Term Debt	32,000	71,000
Retirements of Rate Reduction Bonds	(43,493)	(43,548)
Net Cash Flows Provided by/(Used in) Financing Activities	(11,983)	(30,138)
Net Increase/(Decrease) in Cash	3,414	(230)
Cash - Beginning of Year	13,695	9,373
Cash - End of Year	$ 17,109	$ 9,143