Short-term Investments

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

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



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



Type of securities as of December 31, 2018	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Corporate debt securities	$	47,299	$	1	$	(21	)	$	47,279
U.S. government-related debt securities	14,972		—		(11		)	14,961
Asset-backed securities	7,410		—		(9		)	7,401
Total available-for-sale debt securities	$	69,681	$	1	$	(41	)	$	69,641

The fair values of available-for-sale debt securities by contractual maturity at December 31 were as follows (in thousands):



	2019		2018
Maturing in one year or less	$	101,751	$	69,641
Maturing in one to three years	15,553		—
Total available-for-sale debt securities	117,304		69,641

The Company has both the intent and ability to sell its available-for-sale debt and equity securities maturing greater than one year within 12 months from the balance sheet date and, accordingly, has classified these securities as current in the consolidated balance sheets.

The following table summarizes investments that have been in a continuous unrealized loss position as of December 31, 2019 (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	$	2,515	$	(2	)	$	—	$	—	$	2,515	$	(2	)
Total	$	2,515	$	(2	)	$	—	$	—	$	2,515	$	(2	)

The Company invests in securities that are rated investment grade or better. The unrealized losses on available-for-sale debt securities as of December 31, 2019 and December 31, 2018 were primarily caused by interest rate increases.

The Company reviews the individual securities in its portfolio to determine whether a decline in a security’s fair value below the amortized cost basis is other-than-temporary. The Company determined that as of December 31, 2019, there were no investments in its portfolio that were other-than-temporarily impaired.