The following is a summary of our marketable securities as of September 30, 2018 and December 31, 2017 (in thousands):



	September 30, 2018
			Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
Short-term marketable securities:*
Corporate debt securities	$	53,862	$	1	$	(174	)	$	53,689
Certificates of deposit	13,000		—		—			13,000
U.S. treasury and government agency securities	6,149		—		(29		)	6,120
Commercial paper	5,462		—		—			5,462
Total short-term marketable securities	$	78,473	$	1	$	(203	)	$	78,271
Long-term marketable securities:**
Corporate debt securities	$	55,017	$	2	$	(580	)	$	54,439
U.S. treasury and government agency securities	6,236		—		(78		)	6,158
Certificates of deposit	1,500		—		—			1,500
Total long-term marketable securities	62,753		2		(658		)	62,097
Total marketable securities	$	141,226	$	3	$	(861	)	$	140,368

* Represents marketable securities with a remaining maturity of less than one year.

** Represents marketable securities with a remaining maturity of one to three years.



	December 31, 2017
			Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
Short-term marketable securities:*
Corporate debt securities	$	57,257	$	—	$	(68	)	$	57,189
Certificates of deposit	9,151		—		—			9,151
U.S. treasury and government agency securities	1,999		—		(13		)	1,986
Commercial paper	1,999		—		—			1,999
Total short-term marketable securities	$	70,406	$	—	$	(81	)	$	70,325
Long-term marketable securities:**
Corporate debt securities	$	59,282	$	1	$	(320	)	$	58,963
U.S. treasury and government agency securities	7,381		—		(76		)	7,305
Total long-term marketable securities	66,663		1		(396		)	66,268
Total marketable securities	$	137,069	$	1	$	(477	)	$	136,593

* Represents marketable securities with a remaining maturity of less than one year.

** Represents marketable securities with a remaining maturity of one to three years.