The following is a summary of available-for-sale marketable securities, excluding those securities classified within cash and cash equivalents on the condensed consolidated balance sheets as of September 30, 2020 and December 31, 2019 (in thousands):

	September 30, 2020
	Amortized Cost		Unrealized Gain		Unrealized Losses			Fair Value
Commercial debt securities	$	965,398	$	1,784	$	(154	)	$	967,028
Certificates of deposit		34,225		37		—			34,262
U.S. government treasury securities		169,306		427		(2	)		169,731
Commercial paper		125,218		30		(8	)		125,240
Marketable securities	$	1,294,147	$	2,278	$	(164	)	$	1,296,261

	December 31, 2019
	Amortized Cost		Unrealized Gain		Unrealized Losses			Fair Value
Commercial debt securities	$	80,376	$	46	$	(5	)	$	80,417
U.S. government treasury securities		72,467		10		(4	)		72,473
Commercial paper		23,784		—		—			23,784
Marketable securities	$	176,627	$	56	$	(9	)	$	176,674

As of September 30, 2020, the fair values of available-for-sale marketable securities, by remaining contractual maturity, were as follows (in thousands):

The Company does not believe that any unrealized losses are attributable to credit-related factors based on its evaluation of available evidence. To determine whether a decline in value is related to credit loss, the Company evaluates, among other factors: the extent to which the fair value is less than the amortized cost basis, changes to the rating of the security by a rating agency and any adverse conditions specifically related to an issuer of a security or its industry. Unrealized gain and losses on marketable securities are presented net of tax.