Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2020

Marketable Securities [Abstract]

Summary of Available-for-Sale Debt Securities

The following table summarizes the available-for-sale debt securities held at September 30, 2020 and December 31, 2019 and (in thousands):

Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
September 30, 2020
U.S. treasury securities	$	346,066	$	—	$	(84	)	$	345,982
Corporate securities		80,814		—		(86	)		80,728
Total	$	426,880	$	—	$	(170	)	$	426,710

Description	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
December 31, 2019
U.S. treasury securities	$	15,936	$	6	$	—	$	15,942
Total	$	15,936	$	6	$	—	$	15,942