Securities classified as cash, cash equivalents and short-term investments as of March 31, 2018 and December 31, 2017, are summarized below (in thousands). Estimated fair value is based on quoted market prices for these investments.


	March 31, 2018
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	5,506		—		—	$	5,506
Money market funds		57,491		—		—		57,491
U.S. treasury securities		1,000		—		—		1,000
Corporate bonds		2,550				(2)		2,548
Commercial paper		1,200		—		—		1,200
Total cash and cash equivalents	$	67,747	$	—	$	(2)	$	67,745
Short-term investments
Corporate bonds		27,332		—		(60)		27,272
Commercial paper		28,512		—		(19)		28,493
Asset-backed securities		3,949		—		(10)		3,939
Total short-term investments	$	59,793	$	—	$	(89)	$	59,704
Total cash equivalents and investments	$	127,540	$	—	$	(91)	$	127,449


	December 31, 2017
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
Cash and cash equivalents:
Cash	$	5,882	$	—	$	—	$	5,882
Money market funds		68,651		—		—		68,651
Commercial paper		850		—		—		850
Total cash equivalents and investments	$	75,383	$	—	$	—	$	75,383
Short-term investments
U.S. treasury securities	$	3,994		—		(1)	$	3,993
Corporate bonds		26,853		—		(26)		26,827
Commercial paper		19,584		—		(14)		19,570
Asset-backed securities		8,209		—		(6)		8,203
Total short-term investments	$	58,640	$	—	$	(47)	$	58,593
Total cash equivalents and investments	$	134,023	$	—	$	(47)	$	133,976