XML 112 R93.htm IDEA: XBRL DOCUMENT
v3.22.2

COMMITMENTS AND CONTINGENCIES - Eversource and NSTAR Electric Boston Harbor Civil Action (Details) | 12 Months Ended
--- | ---
Dec. 31, 2016 kV
Commitments and Contingencies Disclosure [Abstract] |
Amount of capacity required for installation of distribution cable (in kV) | 115

X
- Definition Capacity Required For Installation of Distribution Cable + References No definition available. + Details
Name: | es_CapacityRequiredForInstallationofDistributionCable
Namespace Prefix: | es_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration