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Investments

Investments include primarily investment-grade corporate bonds and U.S. Treasury obligations having maturities of up to five years (the "bond portfolio"). Investments in the bond portfolio are reported as available-for-sale and are carried at fair value. Investments maturing less than one year from the balance sheet date are included in short-term investments and investments maturing more than one year from the balance sheet date are included in other assets in the consolidated balance sheets. Management has performed an analysis of the nature of the unrealized losses on available-for-sale investments to determine whether such losses are other-than-temporary. Unrealized losses, representing the excess of the purchase price of an investment over its fair value as of the end of a period, considered to be other-than-temporary are to be included as a charge in the statement of income while unrealized losses considered to be temporary are to be included as a component of equity. Investments whose values are based on quoted market prices in active markets are classified within Level 1. Investments that trade in markets that are not considered to be active, but are valued based on quoted market prices, are classified within Level 2. As Level 2 investments include positions that are not traded in active markets, valuations may be adjusted to reflect illiquidity and/or non-transferability, which are generally based on available market information. Transfers between levels are recognized as of the beginning of the period. Fair value of the bond portfolio was determined using Level 1 inputs related to U.S. Treasury obligations and money market investments and Level 2 inputs related to investment-grade corporate bonds, mortgage-backed securities and direct obligations of government agencies. Unrealized gains, net of unrealized losses, on the investments in the bond portfolio were $786,000 and $760,000 at December 31, 2011 and December 25, 2010, respectively.

The amortized cost and fair market values of available-for-sale investments are as follows at December 31, 2011 and December 25, 2010 (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Market Value
December 31, 2011
Money market investments	$	1,989	$	—	$	—	$	1,989
Mortgage-backed securities		3,017		61		18		3,060
Corporate bonds and direct obligations of government agencies		51,014		819		126		51,707
U.S. Treasury obligations		11,682		51		1		11,732

Total	$	67,702	$	931	$	145	$	68,488

December 25, 2010
Money market investments	$	535	$	—	$	—	$	535
Mortgage-backed securities		3,458		64		8		3,514
Corporate bonds and direct obligations of government agencies		60,330		872		151		61,051
U.S. Treasury obligations		12,584		6		23		12,567

Total	$	76,907	$	942	$	182	$	77,667

For those available-for-sale investments with unrealized losses at December 31, 2011 and December 25, 2010, the following table summarizes the duration of the unrealized loss (in thousands):


	Less than 12 months				12 months or longer				Total
	Fair Market Value		Unrealized Loss		Fair Market Value		Unrealized Loss		Fair Market Value		Unrealized Loss
December 31, 2011
Mortgage-backed securities	$	468	$	18	$	—	$	—	$	468	$	18
Corporate bonds and direct obligations of government agencies		6,067		126		—		—		6,067		126
U.S. Treasury obligations		591		1		—		—		591		1

Total	$	7,126	$	145	$	—	$	—	$	7,126	$	145

December 25, 2010
Mortgage-backed securities	$	225	$	8	$	—	$	—	$	225	$	8
Corporate bonds and direct obligations of government agencies		11,615		151		—		—		11,615		151
U.S. Treasury obligations		774		23		—		—		774		23

Total	$	12,614	$	182	$	—	$	—	$	12,614	$	182

Short-term investments include $27,944,000 in current maturities of investments held by the Company's insurance segment at December 31, 2011. These short-term investments together with $22,239,000 of the non-current portion of investments included in other assets at December 31, 2011 provide collateral for the $45,165,000 of letters of credit issued to guarantee payment of insurance claims.

Investment income represents the earnings on the insurance segment's assets. Investment income earned from the assets of the insurance segment are included as a component of operating income as the investment of these assets is critical to providing collateral, liquidity and earnings with respect to the operation of the Company's insurance programs.