Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2018

Available-for-sale Securities [Abstract]

Cash equivalents and marketable securities classified as available-for-sale

All cash equivalents and marketable securities are classified as available-for-sale. Total cash, cash equivalents and marketable securities are summarized as follows:



	As of June 30, 2018
(In thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	11,078	$	11,078	$	—	$	—		1.75	%
U.S. Government bonds and notes	68,898		68,897		1		—			1.74	%
Corporate notes, bonds, commercial paper and other	177,594		177,639		—		(45		)	1.90	%
Total cash equivalents and marketable securities	257,570		257,614		1		(45		)
Cash	40,770		40,770		—		—
Total cash, cash equivalents and marketable securities	$	298,340	$	298,384	$	1	$	(45	)



	As of December 31, 2017
(In thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	10,915	$	10,915	$	—	$	—		1.16	%
U.S. Government bonds and notes	55,220		55,221		—		(1		)	1.12	%
Corporate notes, bonds, commercial paper and other	195,073		195,204		—		(131		)	1.39	%
Total cash equivalents and marketable securities	261,208		261,340		—		(132		)
Cash	68,168		68,168		—		—
Total cash, cash equivalents and marketable securities	$	329,376	$	329,508	$	—	$	(132	)

Available-for-sale securities reported at fair value

Available-for-sale securities are reported at fair value on the balance sheets and classified as follows:



	As of
	June 30, 2018		December 31, 2017
	(In thousands)
Cash equivalents	$	207,514	$	157,676
Short term marketable securities	50,056		103,532
Total cash equivalents and marketable securities	257,570		261,208
Cash	40,770		68,168
Total cash, cash equivalents and marketable securities	$	298,340	$	329,376

Estimated fair value of cash equivalents and marketable securities classified by the length of time that the securities have been in a continuous unrealized loss position

The estimated fair value of cash equivalents and marketable securities classified by the length of time that the securities have been in a continuous unrealized loss position at June 30, 2018 and December 31, 2017 are as follows:



	Fair Value				Gross Unrealized Loss
	June 30, 2018		December 31, 2017		June 30, 2018			December 31, 2017
	(In thousands)
Less than one year
U.S. Government bonds and notes	$	11,987	$	42,581	$	—		$	(1	)
Corporate notes, bonds and commercial paper	177,594		194,015		(45		)	(131		)
Total Corporate notes, bonds, and commercial paper and U.S. Government bonds and notes	$	189,581	$	236,596	$	(45	)	$	(132	)