Marketable Securities

The Company’s investments have been classified as available-for-sale securities in accordance with U.S. GAAP. Marketable securities are categorized on the Consolidated Balance Sheet as “Marketable securities” within the short-term or long-term classification, as appropriate.

The following table is a summary of available-for-sale securities (in thousands):



As of March 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value (Net Carrying Amount)
Corporate debt securities	$	185,636	$	4	$	(2,318	)	$	183,322
Non-US government securities	14,730		—		(111		)	14,619
Certificates of deposit	500		—		—			500
Agency discount notes	459		—		(4		)	455
Total securities	$	201,325	$	4	$	(2,433	)	$	198,896

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 $2.4 million related to securities with a total amortized cost of approximately $198.2 million at March 31, 2018. No securities had been in a continuous unrealized loss position for more than 12 months as of March 31, 2018. 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 31, 2018, the Company does not consider any of its investments to be other-than-temporarily impaired.



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 a total amortized cost of approximately $99.9 million at March 25, 2017. Four securities had been in a continuous unrealized loss position for more than 12 months as of March 25, 2017. The gross unrealized loss on these securities was less than one tenth of 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 investments by contractual maturity were as follows:



	March 31, 2018				March 25, 2017
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Within 1 year	$	26,560	$	26,397	$	99,868	$	99,813
After 1 year	174,765		172,499		—		—
Total	$	201,325	$	198,896	$	99,868	$	99,813