MARKETABLE SECURITIES (Tables)

6 Months Ended

Jun. 30, 2012

Notes To Consolidated Financial Statements [Abstract]

Schedule Of Available For Sale Securities Reconciliation [Table TextBlock]

		As of June 30, 2012
				Pre-Tax		Pre-Tax
		Amortized		Unrealized		Unrealized
(Millions of Dollars)		Cost		Gains(1)		Losses(1)		Fair Value
NU
	Debt Securities(2)	$	256.1	$	10.9	$	(0.3)	$	266.7
	Equity Securities(2)		134.6		12.0		(5.6)		141.0
WMECO
	Debt Securities		57.5		0.1		(0.1)		57.5
		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(1)	$	52.9	$	52.9	$	18.5	$	18.5
One to five years		53.8		55.0		23.2		23.2
Six to ten years		51.9		54.9		6.0		6.1
Greater than ten years		97.5		103.9		9.8		9.7
Total Debt Securities	$	256.1	$	266.7	$	57.5	$	57.5

Fair Value Heirarchy [Table Text Block]

			NU				WMECO
			As of		As of		As of		As of
(Millions of Dollars)			June 30, 2012		December 31, 2011		June 30, 2012		December 31, 2011
Level 1:
	Mutual Funds and Equity Securities		$	184.8	$	41.1	$	-	$	-
	Money Market Funds			36.3		1.8		3.8		0.1
Total Level 1			$	221.1	$	42.9	$	3.8	$	0.1
Level 2:
	U.S. Government Issued Debt Securities
		(Agency and Treasury)		59.5		11.1		18.7		8.0
	Corporate Debt Securities			31.4		16.5		6.2		9.1
	Asset-Backed Debt Securities			27.4		25.9		6.5		7.9
	Municipal Bonds			96.4		16.1		15.5		15.4
	Other Fixed Income Securities			15.7		18.8		6.8		16.6
Total Level 2			$	230.4	$	88.4	$	53.7	$	57.0
Total Marketable Securities			$	451.5	$	131.3	$	57.5	$	57.1