SHORT-TERM AND LONG-TERM DEBT - Borrowings Outstanding and Available under the Commercial Paper Programs (Details) - Commercial Paper - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Borrowings outstanding	$ 1,393.8	$ 1,343.0
Available borrowing capacity	$ 606.2	$ 657.0
Weighted-average interest rate	0.93%	0.31%
NSTAR Electric
Debt Instrument [Line Items]
Borrowings outstanding	$ 275.0	$ 162.5
Available borrowing capacity	$ 375.0	$ 487.5
Weighted-average interest rate	0.43%	0.14%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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