MARKETABLE SECURITIES (Tables)

9 Months Ended

Sep. 30, 2012

Notes To Consolidated Financial Statements [Abstract]

Schedule Of Available For Sale Securities Reconciliation [Table TextBlock]

		As of September 30, 2012
				Pre-Tax		Pre-Tax
		Amortized		Unrealized		Unrealized
(Millions of Dollars)		Cost		Gains (1)		Losses (1)		Fair Value
NU
	Debt Securities (2)	$	258.5	$	12.3	$	(0.1)	$	270.7
	Equity Securities (2)		142.3		19.7		(2.6)		159.4
WMECO
	Debt Securities		57.6		0.1		(0.1)		57.6
		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)	$	54.4	$	54.4	$	18.4	$	18.4
One to five years		60.2		61.6		25.3		25.3
Six to ten years		46.9		50.0		6.4		6.4
Greater than ten years		97.0		104.7		7.5		7.5
Total Debt Securities	$	258.5	$	270.7	$	57.6	$	57.6

Fair Value Heirarchy [Table Text Block]

			NU				WMECO
			As of		As of		As of		As of
(Millions of Dollars)			September 30, 2012		December 31, 2011		September 30, 2012		December 31, 2011
Level 1:
	Mutual Funds and Equity Securities		$	205.1	$	41.1	$	-	$	-
	Money Market Funds			40.5		1.8		4.7		0.1
Total Level 1			$	245.6	$	42.9	$	4.7	$	0.1
Level 2:
	U.S. Government Issued Debt Securities
		(Agency and Treasury)		59.8		11.1		18.7		8.0
	Corporate Debt Securities			32.2		16.5		7.0		9.1
	Asset-Backed Debt Securities			31.4		25.9		10.7		7.9
	Municipal Bonds			95.3		16.1		12.7		15.4
	Other Fixed Income Securities			11.5		18.8		3.8		16.6
Total Level 2			$	230.2	$	88.4	$	52.9	$	57.0
Total Marketable Securities			$	475.8	$	131.3	$	57.6	$	57.1