MARKETABLE SECURITIES (Tables)

9 Months Ended

Sep. 30, 2011

Notes To Consolidated Financial Statements [Abstract]

Schedule Of Available For Sale Securities Reconciliation [Table TextBlock]

	As of September 30, 2011
			Pre-Tax		Pre-Tax
	Amortized		Unrealized		Unrealized
(Millions of Dollars)	Cost		Gains(1)		Losses(1)		Fair Value
NU	$	87.8	$	1.9	$	(0.3)	$	89.4
WMECO		57.3		-		(0.2)		57.1
	As of December 31, 2010
			Pre-Tax		Pre-Tax
	Amortized		Unrealized		Unrealized
(Millions of Dollars)	Cost		Gains(1)		Losses(1)		Fair Value
NU	$	86.3	$	1.3	$	(0.3)	$	87.3
WMECO		57.2		-		(0.1)		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	$	37.2	$	37.2	$	34.9	$	34.9
One to five years		16.1		16.2		10.7		10.6
Six to ten years		10.7		11.1		6.7		6.7
Greater than ten years		23.8		24.9		5.0		4.9
Total Debt Securities	$	87.8	$	89.4	$	57.3	$	57.1

Fair Value Heirarchy [Table Text Block]

			NU				WMECO
			As of		As of		As of		As of
(Millions of Dollars)			September 30, 2011		December 31, 2010		September 30, 2011		December 31, 2010
Level 1:
	Mutual Funds		$	37.3	$	42.2	$	-	$	-
	Money Market Funds			1.3		1.8		0.4		0.3
Total Level 1			$	38.6	$	44.0	$	0.4	$	0.3
Level 2:
	U.S. Government Issued Debt Securities
		(Agency and Treasury)		2.9		17.8		-		6.0
	Corporate Debt Securities			17.1		22.5		8.5		15.6
	Asset Backed Debt Securities			27.4		11.6		8.5		4.7
	Municipal Bonds			16.4		16.1		15.7		15.4
	Other Fixed Income Securities			24.3		17.5		24.0		15.1
Total Level 2			$	88.1	$	85.5	$	56.7	$	56.8
Total Marketable Securities			$	126.7	$	129.5	$	57.1	$	57.1