The following tables summarize the estimated fair value of the Company’s cash equivalents and marketable securities and the gross unrealized gains and losses (in thousands):

	March 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Cash equivalents
Money market funds	$	9,026	$	—	$	—		$	9,026
Commercial paper		2,495		—		—			2,495
Total cash equivalents		11,521		—		—			11,521

Marketable securities
Commercial paper		7,725		5		—			7,730
Corporate bonds		28,807		8		(147	)		28,668
Total marketable securities	$	36,532	$	13	$	(147	)	$	36,398

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Cash equivalents
Money market funds	$	7,023	$	—	$	—		$	7,023
Reverse repurchase agreements		6,250		—		—			6,250
Commercial paper		2,247		—		—			2,247
Total cash equivalents		15,520		—		—			15,520

Marketable securities
Commercial paper		12,931		15		—			12,946
Corporate bonds		39,714		45		(9	)		39,750
Total marketable securities	$	52,645	$	60	$	(9	)	$	52,696

The reverse repurchase agreements are settled in cash nightly, and as such are classified as cash equivalents.

The following table summarizes available-for-sale securities in an unrealized loss position for which an allowance for credit losses has not been recorded at March 31, 2020 and December 31, 2019, aggregated by major security type and length of time in a continuous unrealized loss position:

	March 31, 2020
	Less Than 12 Months					12 Months or Longer				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	—	$	—		$	—	$	—	$	—	$	—
Corporate bonds		22,810		(147	)		—		—		22,810		(147	)
Total marketable securities	$	22,810	$	(147	)	$	—	$	—	$	22,810	$	(147	)

	December 31, 2019
	Less Than 12 Months					12 Months or Longer				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	—	$	—		$	—	$	—	$	—	$	—
Corporate bonds		13,022		(9	)		—		—		13,022		(9	)
Total marketable securities	$	13,022	$	(9	)	$	—	$	—	$	13,022	$	(9	)

As of March 31, 2020 and December 31, 2019, the Company held 25 and 13 debt securities, respectively, that were in an unrealized loss position. The Company evaluated its securities for credit losses and considered the decline in market

value to be primarily attributable to current economic and market conditions and not attributable to a credit loss or other factors. Additionally, the Company does not intend to sell the securities in an unrealized loss position and does not expect they will be required to sell the securities before recovery of the unamortized cost basis. As of March 31, 2020 and December 31, 2019, an allowance for credit losses had not been recognized and no marketable securities were considered impaired.

There were no realized gains or losses on marketable securities for the three months ended March 31, 2020 and 2019. Interest on marketable securities is included in interest income. Accrued interest receivable on available-for-sale debt securities totaled $0.2 million and $0.3 million at March 31, 2020 and December 31, 2019, respectively, and is excluded from the estimate of credit losses.

The following table summarizes the contractual maturities of the Company’s marketable securities at estimated fair value (in thousands):

	March 31,		December 31,
	2020		2019
Due in one year or less	$	36,398	$	49,687
Due in 1 - 2 years		—		3,009
Total marketable securities	$	36,398	$	52,696

The Company may sell investments at any time for use in current operations even if they have not yet reached maturity. As a result, the Company classifies marketable securities, including securities with maturities beyond twelve months as current assets