Short-term Investments (Tables)

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Short-Term Investments Available-for-Sale Securities

Short-term investments consisted of available-for-sale and equity securities as follows (in thousands):

Type of securities as of March 31, 2020	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Corporate debt securities	$	68,049	$	6	$	(131	)	$	67,924
U.S. government-related debt securities	26,519		213		—			26,732
Asset-backed securities	8,952		6		(10		)	8,948
Total available-for-sale debt securities	$	103,520	$	225	$	(141	)	$	103,604
Corporate equity securities	10,518		—		(1,360		)	9,158
Total short-term investment securities	$	114,038	$	225	$	(1,501	)	$	112,762

Type of securities as of December 31, 2019	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Corporate debt securities	$	78,243	$	89	$	(2	)	$	78,330
U.S. government-related debt securities	26,966		37		—			27,003
Asset-backed securities	11,950		21		—			11,971
Total available-for-sale debt securities	$	117,159	$	147	$	(2	)	$	117,304
Corporate equity securities	9,893		625		—			10,518
Total short-term investment securities	$	127,052	$	772	$	(2	)	$	127,822

Fair Values of Available-for-Sale Securities by Contractual Maturity

The fair values of available-for-sale debt securities by contractual maturity were as follows (in thousands):

	March 31, 2020		December 31, 2019
Maturing in one year or less	$	90,170	$	101,751
Maturing in one to three years	13,434		15,553
Total available-for-sale debt securities	$	103,604	$	117,304

Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value

The following table summarizes investments that have been in a continuous unrealized loss position as of March 31, 2020 (in thousands).

	Less than 12 months					12 months or greater				Total
	Fair Value		Gross unrealized losses			Fair Value		Gross unrealized losses		Fair Value		Gross unrealized losses
Corporate debt securities	$	40,886	$	(131	)	$	—	$	—	$	40,886	$	(131	)
Asset-backed securities	4,952		(10		)	—		—		4,952		(10		)
Total	$	45,838	$	(141	)	$	—	$	—	$	45,838	$	(141	)