Contractual Obligations with Yankee Companies (Details) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2012

Dec. 31, 2013

As of December 31, 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

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.

CYAPC [Member] | DOE Phase I Damages [Member]

Gain Contingency [Line Items]

Awards Received from Litigation

$ 39.6

CYAPC [Member] | DOE Phase II Damages [Member]

Gain Contingency [Line Items]

Awards Received from Litigation

126.3

YAEC [Member] | DOE Phase I Damages [Member]

Gain Contingency [Line Items]

Awards Received from Litigation

38.3