Short-term Investments (Tables)

9 Months Ended

Sep. 30, 2019

Investments, Debt and Equity Securities [Abstract]

Short-Term Investments Available-for-Sale Securities

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

Type of securities as of September 30, 2019	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Corporate debt securities	$	66,299	$	148	$	—	$	66,447
U.S. government-related debt securities	28,431		48		—		28,479
Asset-backed securities	10,476		21		—		10,497
Total available-for-sale securities	$	105,206	$	217	$	—	$	105,423

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 securities	$	69,681	$	1	$	(41	)	$	69,641

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

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

	September 30, 2019		December 31, 2018
Maturing in one year or less	$	97,894	$	69,641
Maturing in one to three years	7,529		—
Total available-for-sale securities	$	105,423	$	69,641