Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2019

Investments All Other Investments [Abstract]

Cash Equivalents, Restricted Cash and Short-Term Investments Classified as Available-for-sale Securities

Cash equivalents, restricted cash and short-term investments (debt securities) which are classified as available-for-sale securities, consisted of the following (in thousands):

September 30, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Money market funds (cash equivalents)	$	21,752	$	—	$	—	$	21,752
U.S. government agency securities		48,439		14		—		48,453
Federal agency securities		13,462		17		—		13,479
Total financial assets	$	83,653	$	31	$	—	$	83,684
Classified as:
Cash and cash equivalents							$	21,752
Short-term investments								61,932
							$	83,684

December 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds (cash equivalents)	$	29,090	$	—	$	—		$	29,090
Federal agency securities (cash equivalents)		999		—		—			999
Restricted cash (money market funds)		50		—		—			50
U.S. government agency securities		74,144		1		(6	)		74,139
Agency securities		14,774		1		—			14,775
Total financial assets	$	119,057	$	2	$	(6	)	$	119,053
Classified as:
Cash and cash equivalents								$	30,089
Short-term investments									88,914
Restricted cash (money market funds)									50
								$	119,053