v3.25.2
SHORT-TERM AND LONG-TERM DEBT - Borrowings Outstanding and Available under the Commercial Paper Programs (Details) - Commercial Paper - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Debt Instrument [Line Items]    
Borrowings outstanding $ 950.5 $ 1,538.0
Available borrowing capacity $ 1,049.5 $ 462.0
Weighted-average interest rate (in percent) 4.78% 4.76%
NSTAR Electric    
Debt Instrument [Line Items]    
Borrowings outstanding $ 430.0 $ 504.8
Available borrowing capacity $ 220.0 $ 145.2
Weighted-average interest rate (in percent) 4.57% 4.55%