Available-for-Sale Securities (Tables)

3 Months Ended

Mar. 31, 2019

Investments Debt And Equity Securities [Abstract]

Schedule of Available-for-Sale Debt Securities

Available-for-sale debt securities with maturities of more than three months from the date of purchase have been classified as short-term investments, and were as follows (in thousands):

	Amortized Cost		Unrealized Gain		Unrealized Loss			Market Value
March 31, 2019:
U.S. Treasury securities	$	70,654	$	23	$	(6	)	$	70,671
	$	70,654	$	23	$	(6	)	$	70,671
December 31, 2018:
U.S. Treasury securities	$	63,674	$	1	$	(24	)	$	63,651
	$	63,674	$	1	$	(24	)	$	63,651