Contractual Obligations with Yankee Companies (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2015

Dec. 31, 2014

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 Phase II DOE proceeds were completed in 2015.

MYAPC Phase One Damages Proceeds To Member Companies

In accordance with MYAPC's three-year refund plan of the DOE Phase I Damages proceeds, in September 2014, MYAPC returned the second portion of the 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. On September 28, 2015, MYAPC returned the remaining DOE Phase I Damages proceeds to the member companies, including CL&P, NSTAR Electric, PSNH, and WMECO, in the amount of $2.3 million, $0.8 million, $1 million and $0.6 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