Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Fair Value of Available-for-Sale Marketable Securities by Type of Security

As of March 31, 2019 and December 31, 2018 the fair value of available-for-sale marketable securities by type of security was as follows:

	March 31, 2019
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial paper	$	1,981	$	—	$	—		$	1,981
U.S. government obligations		54,570		17		—			54,587
Corporate bonds		73,257		94		(6	)		73,345
	$	129,808	$	111	$	(6	)	$	129,913

	December 31, 2018
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial paper	$	36,723	$	—	$	—		$	36,723
U.S. government obligations		39,910		—		(12	)		39,898
Corporate bonds		94,999		20		(85	)		94,934
	$	171,632	$	20	$	(97	)	$	171,555