ASSET RETIREMENT OBLIGATIONS (Tables)

12 Months Ended

Dec. 31, 2021

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Change in Asset Retirement Obligation

A reconciliation of the beginning and ending carrying amounts of ARO liabilities is as follows:

	As of December 31,
	2021								2020
(Millions of Dollars)	Eversource		CL&P		NSTAR Electric		PSNH		Eversource		CL&P		NSTAR Electric		PSNH
Balance as of Beginning of Year	$	499.7	$	33.4	$	91.8	$	4.4	$	489.5	$	32.0	$	97.5	$	4.2
Liability Assumed Upon CMA Asset Acquisition	—		—		—		—		20.1		—		—		—
Liabilities Incurred During the Year	—		—		—		—		2.1		—		2.1		—
Liabilities Settled During the Year	(23.9)		(0.6)		—		—		(21.8)		(0.7)		(1.0)		—
Accretion	29.4		2.2		4.0		0.3		28.9		2.1		4.3		0.2
Revisions in Estimated Cash Flows	(5.1)		—		1.7		—		(19.1)		—		(11.1)		—
Balance as of End of Year	$	500.1	$	35.0	$	97.5	$	4.7	$	499.7	$	33.4	$	91.8	$	4.4