Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of Fair Value Assets And Liabilities Measured On Recurring Basis

The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy:

	December 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial Assets
Money market funds	$	101,919	$	—	$	—	$	101,919
Restricted money market funds		300		—		—		300
Total financial assets	$	102,219	$	—	$	—	$	102,219

	December 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial Assets
Money market funds	$	146,240	$	—	$	—	$	146,240
Restricted money market funds		300		—		—		300
Total financial assets	$	146,540	$	—	$	—	$	146,540
Financial Liabilities
Warrant liabilities	$	—	$	—	$	45,935	$	45,935
Securities issuance obligation		—		—		10,485	$	10,485
Total financial liabilities	$	—	$	—	$	56,420	$	56,420

Schedule of Fair Value Measurement Inputs and Valuation Techniques

At November 13, 2019, upon the issuance of Series A and Series B warrants and when the securities issuance obligation arose, the Company estimated the fair values of the financial liabilities using the following assumptions:

	Series A Warrant			Series B Warrant			Warrant Issuance Obligation			Common Stock Issuance Obligation
Expected term (in years)		5.2			2.3			5.2		N/A
Expected volatility		43	%		88	%		43	%	N/A
Risk-free interest rate		1.70	%		1.64	%		1.70	%	N/A
Expected dividend yield	— %			— %			— %			N/A
Discount for lack of marketability		30	%		30	%		32	%		32	%

At December 31, 2019, the Company remeasured these liabilities to their fair values using the following assumptions:

	Series A Warrant			Series B Warrant			Warrant Issuance Obligation			Common Stock Issuance Obligation
Expected term (in years)		5.1			2.2			5.1		N/A
Expected volatility		43	%		88	%		43	%	N/A
Risk-free interest rate		1.69	%		1.59	%		1.70	%	N/A
Expected dividend yield	— %			— %			— %			N/A
Discount for lack of marketability		25	%		25	%		25	%		25	%

At January 22, 2020, Series A and Series B warrants were no longer considered to be derivative instruments. The Company remeasured the fair value of the warrant liabilities at the time of reclassification to equity using the following assumptions:

	Series A Warrant			Series B Warrant
Expected term (in years)		5.0			2.1
Expected volatility		43	%		88	%
Risk-free interest rate		1.57	%		1.53	%
Expected dividend yield		—	%		—	%

At January 31, 2020, the securities issuance obligation was settled by the issuance of common stock and a common stock warrant. The Company remeasured the fair value of its common stock issuance obligation based on the value of the common stock at the time of issuance. The warrant issuance obligation was remeasured using the following assumptions:

	Warrant Issuance Obligation
Expected term (in years)		5.0
Expected volatility		43	%
Risk-free interest rate		1.57	%
Expected dividend yield	— %

Schedule of Financial Liabilities Fair Value of Recurring Basis Using Unobservable Inputs

The following table provides a summary of changes in the estimated fair values of the Company’s Level 3 financial liabilities, which were measured at fair value on a recurring basis using unobservable inputs:

	Series A Warrant Liability			Series B Warrant Liability			Warrant Issuance Obligation			Common Stock Issuance Obligation			Total
	(in thousands)
Balance, December 31, 2018	$	—		$	—		$	—		$	—		$	—
Issuance of warrants		17,133			7,876			—			—			25,009
Securities issuance obligation		—			—			1,543			4,903			6,446
Changes in fair value		15,483			5,443			1,493			2,546			24,965
Balance, December 31, 2019		32,616			13,319			3,036			7,449			56,420
Changes in fair value		11,597			4,643			152			1,333			17,725
Settlement of financial liabilities by    securities issuance		—			—			(3,188	)		(8,782	)		(11,970	)
Reclassification to equity		(44,213	)		(17,962	)		—			—			(62,175	)
Balance, December 31, 2020	$	—		$	—		$	—		$	—		$	—