Short-term Investments (Tables)

6 Months Ended

Jun. 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 June 30, 2019	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
Corporate debt securities	$	73,159	$	133	$	—	$	73,292
U.S. government-related debt securities	27,331		49		—		27,380
Asset-backed securities	11,414		23		—		11,437
Total available-for-sale securities	$	111,904	$	205	$	—	$	112,109

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):

	June 30, 2019		December 31, 2018
Maturing in one year or less	$	104,059	$	69,641
Maturing in one to three years	8,050		—
Total available-for-sale securities	$	112,109	$	69,641