Investments (Tables)

3 Months Ended

Mar. 31, 2021

Investments Debt And Equity Securities [Abstract]

Schedule of Available-for-sale Investments

Available-for-sale investments consisted of the following as of March 31, 2021 and December 31, 2020 (in thousands):

	March 31, 2021
	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Short-term marketable securities
U.S. government debt securities	$	528,522	$	578	$	—		$	529,100
Corporate bonds		11,494		46		—			11,540
Total short-term marketable securities	$	540,016	$	624	$	—		$	540,640
Long-term marketable securities
U.S. government debt securities	$	30,681	$	10	$	(3	)	$	30,688
Total long-term marketable securities	$	30,681	$	10	$	(3	)	$	30,688

	December 31, 2020
	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Short-term marketable securities
U.S. government debt securities	$	552,539	$	723	$	(10	)	$	553,252
Corporate bonds		11,497		86		(2	)		11,581
Total short-term marketable securities	$	564,036	$	809	$	(12	)	$	564,833
Long-term marketable securities
U.S. government debt securities	$	118,429	$	98	$	(2	)	$	118,525
Total long-term marketable securities	$	118,429	$	98	$	(2	)	$	118,525

Schedule of Gross Unrealized Holding Losses and Fair Value for Investments in Unrealized Loss Position

The following table presents the gross unrealized holding losses and fair value for investments in an unrealized loss position, and the length of time that individual securities have been in a continuous loss position, as of March 31, 2021 (in thousands):

	Less Than 12 Months					12 Months Or Greater
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
U.S. government debt securities	$	10,240	$	(3	)	$	—	$	—
Corporate bonds		1,503		—			—		—
Total available-for-sale securities	$	11,743	$	(3	)	$	—	$	—