XML 156 R121.htm IDEA: XBRL DOCUMENT v3.20.4
COMMITMENTS AND CONTINGENCIES - Schedule of Number of Sites and Reserves (Details) - site
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Loss Contingencies [Line Items]    
Number of Sites 63 57
The Connecticut Light and Power Company    
Loss Contingencies [Line Items]    
Number of Sites 15 15
NSTAR Electric Company    
Loss Contingencies [Line Items]    
Number of Sites 12 15
Public Service Company of New Hampshire    
Loss Contingencies [Line Items]    
Number of Sites 9 9