Securities classified as cash, cash equivalents and short-term investments as of June 30, 2019 and December 31, 2018, are summarized below (in thousands). Estimated fair value is based on quoted market prices for these investments.


	June 30, 2019
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	4,455		—		—	$	4,455
Money market funds		85,171		—		—		85,171
Total cash and cash equivalents	$	89,626	$	—	$	—	$	89,626
Short-term investments
U.S. treasury notes		2,291		2		—		2,293
U.S. treasury securities		2,293		1		—		2,294
Corporate bonds		7,745		3		—		7,748
Commercial paper		17,674		5		—		17,679
Asset-backed securities		4,296		5		—		4,301
Total short-term investments	$	34,299	$	16	$	—	$	34,315
Total cash equivalents and investments	$	123,925	$	16	$	—	$	123,941


	December 31, 2018
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	3,733	$	—	$	—	$	3,733
Money market funds		73,238		—		—		73,238
Commercial paper		1,797		—		—		1,797
Total cash equivalents and investments	$	78,768	$	—	$	—	$	78,768
Short-term investments
U.S. treasury securities	$	3,996		—		—	$	3,996
Corporate bonds		34,611		—		(21)		34,590
Commercial paper		41,371		—		(14)		41,357
Asset-backed securities		9,381		—		(3)		9,378
Total short-term investments	$	89,359	$	—	$	(38)	$	89,321
Total cash equivalents and investments	$	168,127	$	—	$	(38)	$	168,089