(4) 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 performs 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 shareholders’ 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. Any transfers between levels are recognized as of the beginning of any reporting 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, asset-backed securities and direct obligations of government agencies. Unrealized losses, net of unrealized gains, on the investments in the bond portfolio were $145,000 at December 26, 2015, while unrealized gains, net of unrealized losses, in the bond portfolio were $163,000 at December 27, 2014.

The amortized cost and fair values of available-for-sale investments are as follows at December 26, 2015 and December 27, 2014 (in thousands):


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
December 26, 2015
Money market investments	$	7,594	$	—	$	—	$	7,594
Asset-backed securities		4,523		1		58		4,466
Corporate bonds and direct obligations of government agencies		76,839		190		270		76,759
U.S. Treasury obligations		19,273		5		13		19,265

Total	$	108,229	$	196	$	341	$	108,084

December 27, 2014
Money market investments	$	1,729	$	—	$	—	$	1,729
Asset-backed securities		5,106		1		50		5,057
Corporate bonds and direct obligations of government agencies		76,964		491		284		77,171
U.S. Treasury obligations		19,507		14		9		19,512

Total	$	103,306	$	506	$	343	$	103,469

For those available-for-sale investments with unrealized losses at December 26, 2015 and December 27, 2014, the following table summarizes the duration of the unrealized loss (in thousands):


	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
December 26, 2015
Asset-backed securities	$	4,422	$	58	$	—	$	—	$	4,422	$	58
Corporate bonds and direct obligations of government agencies		39,276		217		562		53		39,838		270
U.S. Treasury obligations		15,093		13		—		—		15,093		13

Total	$	58,791	$	288	$	562	$	53	$	59,353	$	341

December 27, 2014
Asset-backed securities	$	2,006	$	13	$	2,447	$	37	$	4,453	$	50
Corporate bonds and direct obligations of government agencies		19,354		135		11,373		149		30,727		284
U.S. Treasury obligations		6,992		1		760		8		7,752		9

Total	$	28,352	$	149	$	14,580	$	194	$	42,932	$	343

The Company believes that unrealized losses on investments were primarily caused by rising interest rates rather than change in credit quality. The Company expects to recover the amortized cost basis of these securities as it does not intend to sell, and does not anticipate being required to sell, these securities before recovery of the cost basis. For these reasons, the Company does not consider the unrealized losses on these securities to be other-than-temporary at December 26, 2015.

Short-term investments include $48,823,000 in current maturities of investments held by the Company at December 26, 2015. The non-current portion of the bond portfolio of $59,261,000 is included in other assets. The short-term investments, together with $15,188,000 of non-current investments, provide collateral for the $57,610,000 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.