FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping

The fair values provided in the tables below are classified as Level 2 within the fair value hierarchy.  Carrying amounts and estimated fair values are as follows:

	As of December 31,
	2016				2015
Eversource (Millions of Dollars)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Preferred Stock Not Subject to Mandatory Redemption	$	155.6	$	158.3	$	155.6	$	157.9
Long-Term Debt	9,603.2		9,980.5		9,034.5		9,425.9

	CL&P				NSTAR Electric				PSNH				WMECO
(Millions of Dollars)	Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value		Carrying Amount		Fair Value
As of December 31, 2016:
Preferred Stock Not Subject to Mandatory Redemption	$	116.2	$	114.7	$	43.0	$	43.6	$	—	$	—	$	—	$	—
Long-Term Debt	2,766.0		3,049.6		2,078.1		2,201.6		1,072.0		1,109.7		566.5		589.0
As of December 31, 2015:
Preferred Stock Not Subject to Mandatory Redemption	$	116.2	$	114.9	$	43.0	$	43.0	$	—	$	—	$	—	$	—
Long-Term Debt	2,763.7		3,031.6		2,029.8		2,182.4		1,071.0		1,121.2		517.3		551.8