Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2021

Financial Instruments Disclosure [Abstract]

Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities

The following tables summarize the estimated fair value and related valuation input hierarchy of our available-for-sale securities as of each period end:

		Total			Total		Total			Total
		Amortized			Unrealized		Unrealized			Estimated
As of March 31, 2021:	Input Level	Cost			Gain		Loss			Fair Value
		(in thousands)
Money market funds	Level 1	$	138,100		$	—	$	—		$	138,100
U.S. Treasury obligations	Level 2		176,010			72		—			176,082
Government agency obligations	Level 2		25,218			15		(6	)		25,227
Corporate debt obligations	Level 2		61,259			100		(20	)		61,339
Commercial paper	Level 2		22,242			—		—			22,242
Asset-backed securities	Level 2		10,847			8		(8	)		10,847
Total available-for-sale securities			433,676			195		(34	)		433,837
Less: amounts classified as cash equivalents			(149,773	)		—		—			(149,773	)
Amounts classified as short-term investments		$	283,903		$	195	$	(34	)	$	284,064
		Total			Total		Total			Total
		Amortized			Unrealized		Unrealized			Estimated
As of December 31, 2020:	Input Level	Cost			Gain		Loss			Fair Value
		(in thousands)
Money market funds	Level 1	$	168,343		$	—	$	—		$	168,343
U.S. Treasury obligations	Level 2		230,239			113		(6	)		230,346
Government agency obligations	Level 2		22,537			22		(3	)		22,556
Corporate debt obligations	Level 2		50,080			166		(1	)		50,245
Commercial paper	Level 2		17,990			—		—			17,990
Asset-backed securities	Level 2		9,860			10		(5	)		9,865
Total available-for-sale securities			499,049			311		(15	)		499,345
Less: amounts classified as cash equivalents			(199,090	)		—		—			(199,090	)
Amounts classified as short-term investments		$	299,959		$	311	$	(15	)	$	300,255

Amortized Cost and Fair Value of Available for Sale Securities by Contractual Maturity

The amortized cost and fair value of our available-for-sale securities by contractual maturity were as follows:

	As of March 31, 2021				As of December 31, 2020
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
	(in thousands)				(in thousands)
Maturing within one year	$	369,665	$	369,805	$	434,828	$	435,023
Maturing in one to five years		64,011		64,032		64,221		64,322
Total available-for-sale securities	$	433,676	$	433,837	$	499,049	$	499,345

Reconciliation of Cash, Cash Equivalents and Restricted Cash

The following table provides a reconciliation of cash, cash equivalents and restricted cash within the condensed consolidated balance sheets that sum to the total of the same such amounts in the condensed consolidated statement of cash flows:

	March 31,		December 31,
	2021		2020
	(in thousands)
Cash and cash equivalents	$	151,097	$	200,404
Restricted cash - short term		194		194
Restricted cash - long term		1,200		1,200
Total cash, cash equivalents and restricted cash	$	152,491	$	201,798