As of September 30, 2019, the fair value of marketable securities by type of security was as follows (in thousands):

	Amortized		Unrealized		Unrealized		Fair
Description	Cost		Gains		Losses		Value
U.S. government agency securities and treasuries	$	93,532	$	109	$	—	$	93,641
Total	$	93,532	$	109	$	—	$	93,641

As of December 31, 2018, the fair value of marketable securities by type of security was as follows (in thousands):

	Amortized		Unrealized		Unrealized		Fair
Description	Cost		Gains		Losses		Value
U.S. government agency securities and treasuries	$	101,027	$	—	$	(41)	$	100,986
Total	$	101,027	$	—	$	(41)	$	100,986

The estimated fair value and amortized cost of the Company’s available-for-sale securities by contractual maturity are summarized as follows (in thousands):

	September 30, 2019
	Amortized		Fair
	Cost		Value
Due in one year or less	$	93,532	$	93,641
Total	$	93,532	$	93,641

	December 31, 2018
	Amortized		Fair
	Cost		Value
Due in one year or less	$	101,027	$	100,986
Total	$	101,027	$	100,986