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Document and Entity Information (USD $)	9 Months Ended
Document and Entity Information (USD $)	Sep. 30, 2011	Oct. 31, 2011	Jun. 30, 2010
Document And Entity [Line Items]
Entity Registrant Name	NORTHEAST UTILITIES
Document Period End Date	Sep. 30, 2011
Document Type	10-Q
Entity Central Index Key	0000072741
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		177,032,294
Entity Public Float			$ 4,486,982,187
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	2011
Document Fiscal Period Focus	Q3
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