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


	March 31, 2019
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	7,019		—		—	$	7,019
Money market funds		83,521		—		—		83,521
Commercial paper		1,496		—		—		1,496
Total cash and cash equivalents	$	92,036	$	—	$	—	$	92,036
Short-term investments
U.S. treasury notes		2,283		—		—		2,283
U.S. treasury securities		2,279		1		—		2,280
Corporate bonds		20,110		2		—		20,112
Commercial paper		30,559		5		—		30,564
Asset-backed securities		4,281		4		—		4,285
Total short-term investments	$	59,512	$	12	$	—	$	59,524
Total cash equivalents and investments	$	151,548	$	12	$	—	$	151,560


	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