Marketable debt securities, which are classified as available-for-sale, consisted of the following (in thousands):

	December 31, 2019
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	29,377	$	—	$	—		$	29,377
U.S. and foreign commercial paper		4,999		—		—			4,999
U.S. government debt securities		2,550		—		—			2,550
Total cash equivalents		36,926		—		—			36,926
Short-term marketable securities:
U.S. and foreign commercial paper		11,965		7		—			11,972
U.S. and foreign corporate debt securities		8,748		8		(1	)		8,755
U.S. government debt securities		48,647		71		—			48,718
U.S. treasuries		15,057		6		—			15,063
Total short-term marketable securities		84,417		92		(1	)		84,508
Long-term marketable securities
U.S. treasuries		3,025		—		—			3,025
Total long-term marketable securities		3,025		—		—			3,025
Total marketable securities	$	124,368	$	92	$	(1	)	$	124,459

	December 31, 2018
	Amortized Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	14,131	$	—	$	—		$	14,131
Total cash equivalents		14,131		—		—			14,131
Short-term marketable securities:
U.S. and foreign commercial paper		10,638		—		(3	)		10,635
U.S. and foreign corporate debt securities		26,552		2		(21	)		26,533
Asset-backed securities		2,750		—		(2	)		2,748
U.S. government debt securities		81,755		1		(57	)		81,699
U.S. treasuries		34,136		1		(16	)		34,121
Total short-term marketable securities		155,831		4		(99	)		155,736
Total marketable securities	$	169,962	$	4	$	(99	)	$	169,867

At December 31, 2019, the remaining contractual maturities of available-for-sale debt securities were less than two years. There have been no significant realized gains or losses on available-for-sale debt securities for the periods presented. Available-for-sale debt securities that were in a continuous loss position but were not deemed to be other than temporarily impaired were immaterial at both December 31, 2019 and 2018. The Company does not intend to and believes it is not more likely than not that it will be required to sell these debt securities before their maturities.

See Note 3, “Fair Value Measurements,” for further information regarding the fair value of the Company's financial instruments.