MARKETABLE SECURITIES (Tables)

3 Months Ended

Mar. 31, 2012

Notes To Consolidated Financial Statements [Abstract]

Schedule Of Available For Sale Securities Reconciliation [Table TextBlock]

	As of March 31, 2012
			Pre-Tax		Pre-Tax
	Amortized		Unrealized		Unrealized
(Millions of Dollars)	Cost		Gains(1)		Losses(1)		Fair Value
NU	$	90.5	$	2.1	$	(0.1)	$	92.5
WMECO		57.4		0.1		(0.1)		57.4
	As of December 31, 2011
			Pre-Tax		Pre-Tax
	Amortized		Unrealized		Unrealized
(Millions of Dollars)	Cost		Gains(1)		Losses(1)		Fair Value
NU	$	88.4	$	2.0	$	(0.2)	$	90.2
WMECO		57.3		-		(0.2)		57.1

Investments Classified by Contractual Maturity Date [Table Text Block]

	NU				WMECO
	Amortized				Amortized
(Millions of Dollars)	Cost		Fair Value		Cost		Fair Value
Less than one year	$	18.4	$	18.4	$	13.9	$	14.0
One to five years		33.5		33.8		27.4		27.4
Six to ten years		12.0		12.5		6.6		6.6
Greater than ten years		26.6		27.8		9.5		9.4
Total Debt Securities	$	90.5	$	92.5	$	57.4	$	57.4

Fair Value Heirarchy [Table Text Block]

			NU				WMECO
			As of		As of		As of		As of
(Millions of Dollars)			March 31, 2012		December 31, 2011		March 31, 2012		December 31, 2011
Level 1:
	Mutual Funds		$	44.3	$	41.1	$	-	$	-
	Money Market Funds			6.2		1.8		3.1		0.1
Total Level 1			$	50.5	$	42.9	$	3.1	$	0.1
Level 2:
	U.S. Government Issued Debt Securities
		(Agency and Treasury)		22.4		11.1		19.3		8.0
	Corporate Debt Securities			15.4		16.5		7.3		9.1
	Asset-Backed Debt Securities			22.9		25.9		5.1		7.9
	Municipal Bonds			13.6		16.1		12.8		15.4
	Other Fixed Income Securities			12.0		18.8		9.8		16.6
Total Level 2			$	86.3	$	88.4	$	54.3	$	57.0
Total Marketable Securities			$	136.8	$	131.3	$	57.4	$	57.1