Investments (Tables)

6 Months Ended

Jun. 30, 2021

Investments Debt And Equity Securities [Abstract]

Schedule of Available-for-sale Investments

Available-for-sale investments consisted of the following as of June 30, 2021 and December 31, 2020 (in thousands):

	June 30, 2021
	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Short-term marketable securities
U.S. government debt securities	$	403,968	$	257	$	—		$	404,225
Corporate bonds		9,997		5		—			10,002
Total short-term marketable securities	$	413,965	$	262	$	—		$	414,227
Long-term marketable securities
U.S. government debt securities	$	71,328	$	—	$	(43	)	$	71,285
Corporate bonds		19,849		4		(7	)		19,846
Total long-term marketable securities	$	91,177	$	4	$	(50	)	$	91,131

	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 individual securities have been in a continuous loss position, as of June 30, 2021 (in thousands):

	Less Than 12 Months					12 Months Or Greater
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
U.S. government debt securities	$	71,285	$	(43	)	$	—	$	—
Corporate bonds		15,281		(7	)		—		—
Total available-for-sale securities	$	86,566	$	(50	)	$	—	$	—