Marketable Securities (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2018
(In thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	11,230	$	11,230	$	—	$	—		1.51	%
U.S. Government bonds and notes	22,913		22,916		—		(3		)	1.64	%
Corporate notes, bonds, commercial paper and other	197,999		198,180		—		(181		)	1.65	%
Total cash equivalents and marketable securities	232,142		232,326		—		(184		)
Cash	59,078		59,078		—		—
Total cash, cash equivalents and marketable securities	$	291,220	$	291,404	$	—	$	(184	)

	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
	March 31, 2018		December 31, 2017
	(In thousands)
Cash equivalents	$	63,283	$	157,676
Short term marketable securities	168,859		103,532
Total cash equivalents and marketable securities	232,142		261,208
Cash	59,078		68,168
Total cash, cash equivalents and marketable securities	$	291,220	$	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 March 31, 2018 and December 31, 2017 are as follows:

	Fair Value				Gross Unrealized Loss
	March 31, 2018		December 31, 2017		March 31, 2018			December 31, 2017
	(In thousands)
Less than one year
U.S. Government bonds and notes	$	22,913	$	42,581	$	(3	)	$	(1	)
Corporate notes, bonds and commercial paper	196,786		194,015		(181		)	(131		)
Total Corporate notes, bonds, and commercial paper and U.S. Government bonds and notes	$	219,699	$	236,596	$	(184	)	$	(132	)