Cash Equivalents and Investments

3 Months Ended

Mar. 31, 2019

Cash Equivalents And Investments [Abstract]

3. Cash Equivalents and Investments

The fair value of securities, not including cash at March 31, 2019 and December 31, 2018, were as follows (in thousands):

	March 31, 2019
	Amortized		Gross Unrealized					Estimated
	Cost		Gains		Losses			Fair Value
Money market funds	$	23,613	$ —		$ —			$	23,613
U.S. government securities		3,476		1	—				3,477
Corporate notes		11,284		2	—				11,286
Commercial paper		15,744	—		—				15,744
Total available-for-sale marketable debt securities	$	54,117	$	3	$	—		$	54,120
Classified as:
Cash equivalents								$	23,613
Short-term investments									30,507
Total cash equivalents and investments								$	54,120

	December 31, 2018
	Amortized		Gross Unrealized					Estimated
	Cost		Gains		Losses			Fair Value
Money market funds	$	10,606	$	—	$	—		$	10,606
U.S. government securities		9,976		—		(1	)		9,975
Corporate notes		16,514		3		(18	)		16,499
Commercial paper		36,331		—		—			36,331
Total available-for-sale marketable debt securities	$	73,427	$	3	$	(19	)	$	73,411
Classified as:
Cash equivalents								$	15,091
Short-term investments									58,320
Total cash equivalents and investments								$	73,411

The following table summarizes the fair value of the Company’s cash equivalents, short-term and long-term marketable securities classified by maturity (in thousands):

	March 31,		December 31,
	2019		2018
Due within one year	$	54,120	$	73,411
Due after one year through three years		—		—
Total available-for-sale marketable debt securities	$	54,120	$	73,411

The following tables present the Company's available-for-sale securities that were in an unrealized loss position as of March 31, 2019 and December 31, 2018 (in thousands):

	As of March 31, 2019
	Less than 12 months					12 Months or Greater					Total
Assets	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate notes	$	2,498	$	—		$	—	$	—		$	2,498	$	—
Total	$	2,498	$	—		$	—	$	—		$	2,498	$	—

	December 31, 2018
	Less than 12 months					12 Months or Greater					Total
Assets	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
U.S. government securities	$	5,977	$	(1	)	$	—	$	—		$	5,977	$	(1	)
Corporate notes		11,521		(10	)		2,993		(8	)		14,514		(18	)
Total	$	17,498	$	(11	)	$	2,993	$	(8	)	$	20,491	$	(19	)

Available-for-sale securities held as of March 31, 2019 had a weighted average days to maturity of 30 days. As of March 31, 2019, the Company had one investment in an unrealized loss position, and no investment has been in an unrealized loss position for more than 12 months. There have been no material realized gains or realized losses on available-for-sale securities for the periods presented.