Fair Value Measurements (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2021

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of fair value measurements

	Fair Value Measurements as of March 31, 2021
	Level I		Level II		Level III		Total
	(in thousands)
Assets
Cash and cash equivalents	$	334,718	$	—	$	—	$	334,718
Held-to-maturity investments:
Commercial paper		—		116,634		—		116,634
State and municipal bonds		—		15,784		—		15,784
Corporate bonds and notes		—		164,203		—		164,203
Total Assets	$	334,718	$	296,621	$	—	$	631,339

	Fair Value Measurements as of December 31, 2020
	Level I		Level II		Level III		Total
	(in thousands)
Assets
Cash and cash equivalents	$	389,705	$	—	$	—	$	389,705
Held-to-maturity investments:
Treasury securities		—		149,995		—		149,995
Commercial paper		—		37,948		—		37,948
Corporate bonds and notes		—		49,829		—		49,829
Total Assets	$	389,705	$	237,772	$	—	$	627,477

	Fair Value Measurements as of December 31, 2020
	Level I		Level II		Level III		Total
Assets	(in thousands)
Cash and cash equivalents	$	389,705	$	-	$	-	$	389,705
Held-to-maturity investments:
Treasury securities		-		149,995		-		149,995
Commercial paper		-		37,948		-		37,948
Corporate bonds and notes		-		49,829		-		49,829
Total Assets	$	389,705	$	237,772	$	-	$	627,477

	Fair Value Measurements as of December 31, 2019
	Level I		Level II		Level III		Total
Liabilities	(in thousands)
Convertible notes payable derivative liabilities	$	-	$	-	$	8,351	$	8,351
Total Liabilities	$	-	$	-	$	8,351	$	8,351

Schedule of fair value of the convertible debt derivative liabilities

Input	October 1, 2020	Issuance of January 2020 Note (January 2020)	Issuance of December 2019 Note and December 31, 2019	Issuances of Initial 2019 Notes (July 2019)	Issuances of Initial 2019 Notes (June 2019)	Issuances of Initial 2019 Notes (February 2019)
Probability-weighted conversion discount	2.5 - 50.0%	50.0%	23.9 - 50.0%	24.1%	24.4%	24.4%
Remaining term (years)	0.0 - 4.3	5.0	0.7 - 4.5	5.0	2.0	2.0
Equity volatility	NA	NA	63.0 - 71.0%	74.0%	78.0%	75.0%
Risk rate1	19.6 - 57.7%	50.0%	27.2 - 50.0%	29.0%	26.6%	34.2%
Probability of next financing event1	100.0%	70.0%	70.0%	50.0%	50.0%	50.0%
Timing of next financing event1	10/1/2020	9/30/2020	9/30/2020	3/31/2020	3/31/2020	9/30/2019
Probability of default event1	0.0%	30.0%	25.0 - 30.0%	50.0%	50.0%	50.0%
Timing of default event1	NA	9/30/2020	9/30/2020	3/31/2020	3/31/2020	9/30/2019
Probability of sale event1	0.0%	0.0%	0.0 - 5.0%	0.0%	0.0%	0.0%
Timing of sale event1	NA	NA	9/30/2020	NA	NA	NA
Negotiation discount1 2	0.0 - 0.1%	24.2%	21.7%	0.0%	0.0%	0.0%

¹ Represents a Level III unobservable input

² Based on the terms and provisions of the December 2019 and January 2020 Notes, the valuation model incorporated this additional assumption

Schedule of level 3 instruments

Balance, December 31, 2018	$	2,068
Issuance of convertible notes payable derivative liabilities		7,428
Fair value adjustments		(1,145	)
Balance, December 31, 2019		8,351
Issuance of convertible note payable derivative liability		2,656
Fair value adjustments		1,358
Settlement of convertible notes payable derivative liabilities		(12,365	)
Balance, December 31, 2020	$	-