Marketable securities

9 Months Ended

Sep. 30, 2019

Marketable securities

Marketable securities

5. Marketable securities

The following table summarizes marketable securities held at September 30, 2019 and December 31, 2018:

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
September 30, 2019
Commercial paper	$	14,871	$	—	$	—	$	14,871
Corporate bonds		11,984		26		—		12,010
U.S. Treasuries		26,923		2		—		26,925
	$	53,778	$	28	$	—	$	53,806

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
December 31, 2018
U.S. Treasuries	$	10,505	$	—	$	(8)	$	10,497
	$	10,505	$	—	$	(8)	$	10,497