COMMITMENTS AND CONTINGENCIES - Eversource and NSTAR Electric Boston Harbor Civil Action Narrative (Details)	Jul. 15, 2016 kV
Commitments and Contingencies Disclosure [Abstract]
Amount of capacity required for installation of distribution cable (in kV)	115

Capacity Required For Installation of Distribution Cable

No definition available.

Name:	es_CapacityRequiredForInstallationOfDistributionCable
Namespace Prefix:	es_
Data Type:	dtr-types:voltageItemType
Balance Type:	na
Period Type:	duration