XML 63 R77.htm IDEA: XBRL DOCUMENT v2.4.1.9
Related Parties (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
The Connecticut Light And Power Company [Member]    
Related Party Transaction [Line Items]    
Long Term Receivable From Nusco $ 25.0nu_LongTermReceivableFromNusco
/ dei_LegalEntityAxis
= nu_TheConnecticutLightAndPowerCompanyMember		 $ 25.0nu_LongTermReceivableFromNusco
/ dei_LegalEntityAxis
= nu_TheConnecticutLightAndPowerCompanyMember
Public Service Company Of New Hampshire [Member]    
Related Party Transaction [Line Items]    
Long Term Receivable From Nusco 3.8nu_LongTermReceivableFromNusco
/ dei_LegalEntityAxis
= nu_PublicServiceCompanyOfNewHampshireMember		 3.8nu_LongTermReceivableFromNusco
/ dei_LegalEntityAxis
= nu_PublicServiceCompanyOfNewHampshireMember
Western Massachusetts Electric Company [Member]    
Related Party Transaction [Line Items]    
Long Term Receivable From Nusco $ 5.5nu_LongTermReceivableFromNusco
/ dei_LegalEntityAxis
= nu_WesternMassachusettsElectricCompanyMember		 $ 5.5nu_LongTermReceivableFromNusco
/ dei_LegalEntityAxis
= nu_WesternMassachusettsElectricCompanyMember