Marketable Securities (Tables)

3 Months Ended

Apr. 01, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Market Value of AFS Securities

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

Schedule of AFS Securities in Unrealized Loss Position

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	)