Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

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

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

Schedule of AFS Securities in Unrealized Loss Position

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	)

Schedule of Amortized Cost of HTM Securities

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.