Marketable Securities

As noted in Note 2, the Company reclassified all marketable securities from HTM to AFS in the third quarter of 2017, following a change to the Company’s cash reserve investment policy that allows the Company to sell marketable securities prior to maturity. This change resulted in recording a $2.5 million net unrealized loss in other comprehensive income. The reclassification of the investment portfolio to AFS was made to provide increased flexibility in the use of our investments to support current operations.

The following table presents the amortized cost, gross unrealized gains and losses, and fair market value of our AFS securities as of December 31, 2017:



	December 31, 2017
(In thousands)	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Short-term AFS securities
Corporate debt securities	$	150,334	$	—	$	(227	)	$	150,107
U.S. Treasury securities	70,985		—		(34		)	70,951
U.S. governmental agency securities	45,819		—		(179		)	45,640
Certificates of deposit	9,300		—		—			9,300
Commercial paper	32,591		—		—			32,591
Total short-term AFS securities	$	309,029	$	—	$	(440	)	$	308,589
Long-term AFS securities
U.S. governmental agency securities	$	97,798	$	—	$	(1,019	)	$	96,779
Corporate debt securities	92,687		—		(683		)	92,004
U.S. Treasury securities	53,031		—		(403		)	52,628
Total long-term AFS securities	$	243,516	$	—	$	(2,105	)	$	241,411

The following table represents the AFS securities as of December 31, 2017 that were in an unrealized loss position, aggregated by investment category and the length of time that individual securities have been in a continuous loss position:



	December 31, 2017
	Less than 12 Months					12 Months or Greater					Total
(In thousands)	Fair Value		Gross unrealized losses			Fair Value		Gross unrealized losses			Fair Value		Gross unrealized losses
Short-term AFS securities
Corporate debt securities	$	140,111	$	(199	)	$	9,996	$	(28	)	$	150,107	$	(227	)
U.S. Treasury securities	70,951		(34		)	—		—			70,951		(34		)
U.S. governmental agency securities	19,770		(50		)	25,870		(129		)	45,640		(179		)
Total short-term AFS securities	$	230,832	$	(283	)	$	35,866	$	(157	)	$	266,698	$	(440	)
Long-term AFS securities
U.S. governmental agency securities	$	23,998	$	(125	)	$	72,781	$	(894	)	$	96,779	$	(1,019	)
Corporate debt securities	81,118		(579		)	10,886		(104		)	92,004		(683		)
U.S. Treasury securities	52,628		(403		)	—		—			52,628		(403		)
Total long-term AFS securities	$	157,744	$	(1,107	)	$	83,667	$	(998	)	$	241,411	$	(2,105	)

We periodically review our AFS securities for OTTI. See Note 2 for factors we consider when assessing AFS securities for OTTI. As of December 31, 2017, we did not intend to sell and it was not likely that we would be required to sell these investments before recovery of their amortized cost basis, which may be at maturity. Unrealized losses related to these investments are primarily due to interest rate fluctuations as opposed to changes in credit quality. Therefore, as of December 31, 2017, we have recognized no OTTI loss.

The following table presents the amortized cost of our HTM securities as of December 25, 2016:



	December 25, 2016
(In thousands)	Amortized Cost
Short-term HTM securities⁽¹⁾
U.S. Treasury securities	$	150,623
Corporate debt securities	150,599
U.S. governmental agency securities	64,135
Commercial paper	84,178
Total short-term HTM securities	$	449,535
Long-term HTM securities⁽¹⁾
U.S. governmental agency securities	$	110,732
Corporate debt securities	61,775
U.S. Treasury securities	14,792
Total long-term HTM securities	$	187,299

⁽¹⁾ All HTM securities were recorded at amortized cost and not adjusted to fair value in accordance with the HTM accounting treatment. As of December 25, 2016, the amortized cost approximated fair value because of the short-term maturity and highly liquid nature of these investments.

Marketable debt securities

As of December 31, 2017, our short-term and long-term marketable securities had remaining maturities of less than 1 month to 12 months and 13 months to 35 months, respectively. See Note 8 for additional information regarding the fair value hierarchy of our marketable securities.

Letters of credit

We issued letters of credit totaling $56.0 million as of December 31, 2017, to secure commitments under certain sub-lease agreements associated with the rental of floors in our headquarters building. The letters of credit will expire in 2019, and are collateralized by marketable securities, with a fair value of $63.1 million, held in our investment portfolios. No amounts were outstanding on these letters of credit as of December 31, 2017. See Note 18 for additional information regarding the securities commitment.