Short-term Investments (Tables)

12 Months Ended

Dec. 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 December 31, 2020	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Corporate debt securities	$	22,338	$	71	$	—	$	22,409
U.S. government-related debt securities	5,000		3		—		5,003
Asset-backed securities	1,462		9		—		1,471
Total available-for-sale debt securities	$	28,800	$	83	$	—	$	28,883

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 at December 31 were as follows (in thousands):

	2020		2019
Maturing in one year or less	$	28,883	$	101,751
Maturing in one to three years	—		15,553
Total available-for-sale debt securities	28,883		117,304