Financial Instruments

12 Months Ended

Dec. 31, 2022

Financial Instruments Disclosure [Abstract]

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 December 31, 2022:	Input Level	Cost			Gain			Loss			Fair Value
		(in thousands)
Money market funds	Level 1	$	78,033		$	—		$	—		$	78,033
U.S. Treasury obligations	Level 2		63,013			3			(394	)		62,622
Government agency obligations	Level 2		8,086			—			(48	)		8,038
Corporate debt obligations	Level 2		82,598			4			(1,513	)		81,089
Commercial paper	Level 2		996			—			—			996
Asset-backed securities	Level 2		6,343			—			(119	)		6,224
Total available-for-sale securities			239,069			7			(2,074	)		237,002
Less: amounts classified as cash equivalents			(87,122	)		(3	)		—			(87,125	)
Amounts classified as short-term investments		$	151,947		$	4		$	(2,074	)	$	149,877

		Total			Total			Total			Total
		Amortized			Unrealized			Unrealized			Estimated
As of December 31, 2021:	Input Level	Cost			Gain			Loss			Fair Value
		(in thousands)
Money market funds	Level 1	$	89,738		$	—		$	—		$	89,738
U.S. Treasury obligations	Level 2		111,832			1			(138	)		111,695
Government agency obligations	Level 2		21,346			—			(23	)		21,323
Corporate debt obligations	Level 2		99,757			6			(190	)		99,573
Commercial paper	Level 2		36,993			—			—			36,993
Asset-backed securities	Level 2		10,174			1			(25	)		10,150
Total available-for-sale securities			369,840			8			(376	)		369,472
Less: amounts classified as cash equivalents			(104,488	)		—			—			(104,488	)
Amounts classified as short-term investments		$	265,352		$	8		$	(376	)	$	264,984

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


	As of December 31, 2022				As of December 31, 2021
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
	(in thousands)				(in thousands)
Maturing within one year	$	202,323	$	201,359	$	278,457	$	278,354
Maturing in one to five years		36,746		35,643		91,383		91,118
Total available-for-sale securities	$	239,069	$	237,002	$	369,840	$	369,472

We considered the current and expected future global economic and market conditions, including the COVID-19 pandemic and the war in Ukraine, and determined that our investments have not been significantly impacted. As of December 31, 2022, no significant facts or circumstances were present to indicate a deterioration in the creditworthiness of the issuers of the available-for-sale securities we hold, and we have no requirement or intention to sell these securities before maturity or recovery of their amortized cost basis. For all securities with a fair value less than its amortized cost basis, we determined the decline in fair value below amortized cost basis to be non-credit related and no allowance for losses has been recorded. During the years ended December 31, 2022, 2021 and 2020, we did not recognize any impairment losses on our investments.

We have elected the practical expedient to exclude the applicable accrued interest from both the fair value and the amortized cost basis of our available-for-sale securities for purposes of identifying and measuring an impairment. We present accrued interest receivable related to our available-for-sale securities in other current assets, separate from short-term investments on our consolidated balance sheet. As of December 31, 2022 and 2021, accrued interest receivable was $0.8 million and $0.8 million, respectively. Our accounting policy is to not measure an allowance for credit losses for accrued interest receivables and to write-off any uncollectible accrued interest receivable as a reversal of interest income in a timely manner, which we consider to be in the period in which we determine the accrued interest will not be collected by us. We have not written off any accrued interest receivables for the years ended December 31, 2022, 2021 and 2020.

In addition, restricted cash collateralized by money market funds is a financial asset measured at fair value and is a Level 1 financial instrument under the fair value hierarchy.

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


	December 31,		December 31,
	2022		2021
	(in thousands)
Cash and cash equivalents	$	92,942	$	106,084
Restricted cash - short-term		146		194
Restricted cash - long-term		—		1,200
Total cash, cash equivalents and restricted cash	$	93,088	$	107,478