MARKETABLE SECURITIES

The Company recorded $3.9 million and $2.5 million of net unrealized loss in AOCI as of April 1, 2018, and December 31, 2017, respectively.

The following tables present the amortized cost, gross unrealized gains and losses, and fair market value of our AFS debt securities as of April 1, 2018, and December 31, 2017:



	April 1, 2018
(In thousands)	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Short-term AFS securities
Corporate debt securities	$	147,292	$	—	$	(460	)	$	146,832
U.S Treasury securities	71,460		1		(62		)	71,399
U.S. governmental agency securities	60,240		—		(287		)	59,953
Commercial paper	15,450		—		—			15,450
Certificates of deposit	6,200		—		—			6,200
Total short-term AFS securities	$	300,642	$	1	$	(809	)	$	299,834
Long-term AFS securities
Corporate debt securities	$	99,699	$	2	$	(1,326	)	$	98,375
U.S. governmental agency securities	86,526		1		(1,113		)	85,414
U.S Treasury securities	52,522		—		(670		)	51,852
Total long-term AFS securities	$	238,747	$	3	$	(3,109	)	$	235,641



	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
Commercial paper	32,591		—		—			32,591
Certificates of deposit	9,300		—		—			9,300
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 tables represent the AFS securities as of April 1, 2018, and 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:



	April 1, 2018
	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	$	137,958	$	(373	)	$	8,874	$	(87	)	$	146,832	$	(460	)
U.S Treasury securities	69,009		(62		)	—		—			69,009		(62		)
U.S. governmental agency securities	19,797		(39		)	40,156		(248		)	59,953		(287		)
Total short-term AFS securities	$	226,764	$	(474	)	$	49,030	$	(335	)	$	275,794	$	(809	)
Long-term AFS securities
Corporate debt securities	$	91,661	$	(1,244	)	$	4,943	$	(82	)	$	96,604	$	(1,326	)
U.S Treasury securities	23,910		(244		)	58,404		(869		)	82,314		(1,113		)
U.S. governmental agency securities	51,852		(670		)	—		—			51,852		(670		)
Total long-term AFS securities	$	167,423	$	(2,158	)	$	63,347	$	(951	)	$	230,770	$	(3,109	)



	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
Corporate debt securities	$	81,118	$	(579	)	$	10,886	$	(104	)	$	92,004	$	(683	)
U.S Treasury securities	23,998		(125		)	72,781		(894		)	96,779		(1,019		)
U.S. governmental agency securities	52,628		(403		)	—		—			52,628		(403		)
Total long-term AFS securities	$	157,744	$	(1,107	)	$	83,667	$	(998	)	$	241,411	$	(2,105	)

We conduct an other-than-temporary impairment (“OTTI”) analysis on a quarterly basis or more often if a potential loss-triggering event occurs. We consider factors such as the duration, severity and the reason for the decline in value, the potential recovery period and whether we intend to sell. For AFS securities, we also consider whether (i) it is more likely than not that we will be required to sell the debt securities before recovery of their amortized cost basis and (ii) the amortized cost basis cannot be recovered as a result of credit losses.

As of April 1, 2018, 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 April 1, 2018, we have recognized no OTTI loss.

As of April 1, 2018, 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 9 for more information regarding the fair value of our marketable securities.

Letters of credit

We arranged for the issuance of 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 held in our investment portfolios, with a fair value of $63.0 million and $63.1 million, as of April 1, 2018, and December 31, 2017, respectively. No amounts were outstanding on these letters of credit as of April 1, 2018. See Note 15 for more information regarding the letters of credit.