The Company elects to record mutual funds purchased by the NU supplemental benefit trust at fair value. As such, any change in fair value of these purchased equity securities are reflected in Net Income. These equity securities, classified as Level 1 in the fair value hierarchy, totaled $44.4 million and $42.2 million as of June 30, 2011 and December 31, 2010, respectively, and are included in current Marketable Securities. Gains on these securities of $0.3 million and $2.2 million for the three and six months ended June 30, 2011 and losses of $4.2 million and $2.5 million for the three and six months ended June 30, 2010, respectively, were recorded in Other Income, Net on the accompanying unaudited condensed consolidated statements of income. Dividend income is recorded when dividends are declared and are recorded in Other Income, Net on the accompanying unaudited condensed consolidated statements of income. All other marketable securities are accounted for as available-for-sale.

Available-for-Sale Securities: The following is a summary by security type of NU's available-for-sale securities held in the NU supplemental benefit trust and WMECO's spent nuclear fuel trust. These securities are recorded at fair value and included in current and long-term Marketable Securities on the accompanying unaudited condensed consolidated balance sheets.

		As of June 30, 2011
				Pre-Tax		Pre-Tax
		Amortized		Unrealized		Unrealized
(Millions of Dollars)		Cost		Gains⁽¹⁾		Losses⁽¹⁾		Fair Value
NU
U.S. Government Issued Debt Securities
	(Agency and Treasury)	$	13.1	$	0.3	$	-	$	13.4
Corporate Debt Securities			12.6		0.5		-		13.1
Asset Backed Debt Securities			9.4		0.4		(0.1)		9.7
Municipal Bonds			26.4		0.1		-		26.5
Money Market Funds and Other			25.5		0.2		-		25.7
Total NU		$	87.0	$	1.5	$	(0.1)	$	88.4

WMECO Spent Nuclear Fuel Trust
Corporate Debt Securities		$	5.9	$	-	$	-	$	5.9
Asset Backed Debt Securities			3.1		-		(0.1)		3.0
Municipal Bonds			25.8		-		-		25.8
Money Market Funds and Other			22.4		-		-		22.4
Total WMECO Spent Nuclear Fuel Trust		$	57.2	$	-	$	(0.1)	$	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
U.S. Government Issued Debt Securities
	(Agency and Treasury)	$	17.7	$	0.2	$	(0.1)	$	17.8
Corporate Debt Securities			22.1		0.5		(0.1)		22.5
Asset Backed Debt Securities			11.3		0.4		(0.1)		11.6
Municipal Bonds			16.1		-		-		16.1
Money Market Funds and Other			19.1		0.2		-		19.3
Total NU		$	86.3	$	1.3	$	(0.3)	$	87.3

WMECO Spent Nuclear Fuel Trust
U.S. Government Issued Debt Securities
	(Agency and Treasury)	$	6.0	$	-	$	-	$	6.0
Corporate Debt Securities			15.6		-		-		15.6
Asset Backed Debt Securities			4.8		-		(0.1)		4.7
Municipal Bonds			15.4		-		-		15.4
Money Market Funds and Other			15.4		-		-		15.4
Total WMECO Spent Nuclear Fuel Trust		$	57.2	$	-	$	(0.1)	$	57.1

(1) Unrealized gains and losses on debt securities for the NU supplemental benefit trust and WMECO spent nuclear fuel trust are recorded in AOCI and Other Long-Term Assets, respectively, on the accompanying unaudited condensed consolidated balance sheets.

Unrealized Losses and Other-than-Temporary Impairment: There have been no significant unrealized losses, other-than-temporary impairments or credit losses for the NU supplemental benefit trust or WMECO spent nuclear fuel trust. Factors considered in determining whether a credit loss exists include the duration and severity of the impairment, adverse conditions specifically affecting the issuer, and the payment history, ratings and rating changes of the security. For asset backed debt securities, underlying collateral and expected future cash flows are also evaluated.

Realized gains and losses: Realized gains and losses on available-for-sale-securities are recorded in Other Income, Net for the NU supplemental benefit trust and in Other Long-Term Assets for the WMECO spent nuclear fuel trust. NU utilizes the specific identification basis method for the NU supplemental benefit trust securities and the average cost basis method for the WMECO spent nuclear fuel trust to compute the realized gains and losses on the sale of available-for-sale securities.

Contractual Maturities: As of June 30, 2011, the contractual maturities of available-for-sale debt securities are as follows:


	NU				WMECO
	Amortized				Amortized
(Millions of Dollars)	Cost		Fair Value		Cost		Fair Value
Less than one year	$	30.2	$	30.3	$	28.0	$	28.0
One to five years		12.3		12.5		6.7		6.8
Six to ten years		6.3		6.7		2.0		1.9
Greater than ten years		38.2		38.9		20.5		20.4
Total Debt Securities	$	87.0	$	88.4	$	57.2	$	57.1

Fair Value Measurements: The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy:

			NU				WMECO
			As of		As of		As of		As of
(Millions of Dollars)			June 30, 2011		December 31, 2010		June 30, 2011		December 31, 2010
Level 1:
	Mutual Funds		$	44.4	$	42.2	$	-	$	-
	Money Market Funds			2.1		1.8		1.1		0.3
Total Level 1			$	46.5	$	44.0	$	1.1	$	0.3
Level 2:
	U.S. Government Issued Debt Securities
		(Agency and Treasury)		13.4		17.8		-		6.0
	Corporate Debt Securities			13.1		22.5		5.9		15.6
	Asset Backed Debt Securities			9.7		11.6		3.0		4.7
	Municipal Bonds			26.5		16.1		25.8		15.4
	Other Fixed Income Securities			23.6		17.5		21.3		15.1
Total Level 2			$	86.3	$	85.5	$	56.0	$	56.8
Total Marketable Securities			$	132.8	$	129.5	$	57.1	$	57.1

U.S. government issued debt securities are valued using market approaches that incorporate transactions for the same or similar bonds and adjustments for yields and maturity dates. Corporate debt securities are valued using a market approach, utilizing recent trades of the same or similar instrument and also incorporating yield curves, credit spreads and specific bond terms and conditions. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Asset backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates and tranche information. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.