Short-Term Investments (Tables)

3 Months Ended

Mar. 31, 2021

Investments Debt And Equity Securities [Abstract]

Schedule of Cost, Gross Unrealized Holding Gains, Gross Unrealized Holding Losses and Fair Value of Available for Sale Investments

The cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale investments by types and classes of security at March 31, 2021 and December 31, 2020 consisted of the following (in thousands):

At March 31, 2021	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. treasury securities	$	173,916	$	17	$	—		$	173,933
Total	$	173,916	$	17	$	—		$	173,933
At December 31, 2020
U.S. treasury securities	$	215,185	$	—	$	(31	)	$	215,154
Total	$	215,185	$	—	$	(31	)	$	215,154