Marketable Securities

6 Months Ended

Jun. 30, 2019

Investments Debt And Equity Securities [Abstract]

Marketable Securities

4. Marketable Securities

As of June 30, 2019 and December 31, 2018 the fair value of available-for-sale marketable securities by type of security was as follows:

	June 30, 2019
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Commercial paper	$	1,996					$	1,996
U.S. government obligations		64,727		80				64,807
Corporate bonds		63,908		150				64,058
	$	130,631	$	230	$	—	$	130,861

	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

As of June 30, 2019 and December 31, 2018, marketable securities consisted of approximately $125.8 and $171.6 million, respectively, of investments that mature within twelve months. As of June 30, 2019, long-term investments consisted of approximately $5.1 million of investments that mature after one year but within two years from the balance sheet date. There were no investments with maturities greater than twelve months as of December 31, 2018.