Marketable Securities

The Company’s investments that have original maturities greater than 90 days have been classified as available-for-sale securities in accordance with U.S. GAAP. Marketable securities are categorized on the consolidated condensed balance sheet as short- and long-term marketable securities, as appropriate.

The following table is a summary of available-for-sale securities at September 23, 2017 (in thousands):



As of September 23, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value (Net Carrying Amount)
Corporate debt securities	$	135,219	$	103	$	(89	)	$	135,233
Non-US government securities	11,817		—		(14		)	11,803
US Treasury securities	998		—		—			998
Certificates of deposit	500		—		—			500
Agency discount notes	459		—		—			459
Total securities	$	148,993	$	103	$	(103	)	$	148,993

The Company typically invests in highly-rated securities with original maturities generally ranging from one to three years. The Company's specifically identified gross unrealized loss of $103 thousand related to securities with total amortized cost of approximately $78.2 million at September 23, 2017. No securities have been in a continuous unrealized loss position for more than 12 months as of September 23, 2017. The Company may sell certain of its marketable securities prior to their stated maturities for strategic reasons including, but not limited to, anticipated or actual changes in credit rating and duration management. When evaluating an investment for other-than-temporary impairment, the Company reviews factors including the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer, changes in market interest rates and whether it is more likely than not the Company will be required to sell the investment before recovery of the investment’s cost basis. As of September 23, 2017, the Company does not consider any of its investments to be other-than-temporarily impaired.

The following table is a summary of available-for-sale securities at March 25, 2017 (in thousands):

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As of March 25, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value (Net Carrying Amount)
Corporate debt securities	33,350		$	—	$	(20	)	$	33,330
Commercial paper	66,518		—		(35		)	66,483
Total securities	$	99,868	$	—	$	(55	)	$	99,813

The Company’s specifically identified gross unrealized losses of $55 thousand related to securities with total amortized cost of approximately $99.9 million at March 25, 2017. Four securities had been in a continuous loss position for more than 12 months as of March 25, 2017. The gross unrealized loss on these securities was less than one percent of the position value. The Company may sell certain of its marketable securities prior to their stated maturities for strategic reasons including, but not limited to, anticipated or actual changes in credit rating and duration management. When evaluating an investment for other-than-temporary impairment, the Company reviews factors including the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer, changes in market interest rates and whether it is more likely than not the Company will be required to sell the investment before recovery of the investment’s cost basis. As of March 25, 2017, the Company did not consider any of its investments to be other-than-temporarily impaired.

The cost and estimated fair value of available-for-sale securities by contractual maturities were as follows (in thousands):

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	September 23, 2017				March 25, 2017
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
Within 1 year	$	15,454	$	15,446	$	99,868	$	99,813
After 1 year	133,539		133,547		—		—
Total	$	148,993	$	148,993	$	99,868	$	99,813