SHORT TERM DEBT (Details) (The Connecticut Light And Power Company [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
The Connecticut Light And Power Company [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	$ 300.0
Short-term Debt, Terms	CL&P Credit Agreement: On March 26, 2012, CL&P entered into a five-year unsecured revolving credit facility in the amount of $300 million, which expires on March 26, 2017. Under this facility, CL&P can borrow either on a short-term or a long-term basis subject to regulatory approval. As of June 30, 2012, CL&P had $300 million in short-term borrowings outstanding under this credit facility, which was recorded in Notes Payable to Banks on the accompanying unaudited condensed consolidated balance sheet. Under this facility, CL&P may borrow at prime rates or LIBOR-based rates, plus an applicable margin based on the higher of S&P’s or Moody’s credit ratings. The weighted-average interest rate on the borrowings outstanding under this facility as of June 30, 2012 was 1.59 percent. In addition, CL&P must comply with certain financial and non-financial covenants, including a consolidated debt to total capitalization ratio. CL&P was in compliance with these covenants as of June 30, 2012. If CL&P was not in compliance with these covenants, an event of default would occur requiring all outstanding borrowings to be repaid and additional borrowings would not be permitted under this credit facility.
Short Term Debt Regulatory Limits	Limits: The amount of short-term borrowings that may be incurred by CL&P are subject to periodic approval by the FERC. On November 30, 2011, the FERC granted authorization to allow CL&P to incur total short-term borrowings up to a maximum of $450 million effective January 1, 2012 through December 31, 2013. On March 22, 2012, FERC approved CL&P's application requesting to increase its total short-term borrowing capacity from a maximum of $450 million to a maximum of $600 million for the authorization period through December 31, 2013.