Note 11 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in dollars per share)			$ 4.98
Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in dollars per share)			$ 56,460
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)			4,670,324	0
Share-based Payment Arrangement, Expense	$ 4,206	$ 674	$ 5,823	$ 1,347
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares (in shares)			0
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	18,700		$ 18,700
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Expense		0		0
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 years 10 months 24 days
Share-based Payment Arrangement, Option [Member] \| Research and Development Expense [Member]
Share-based Payment Arrangement, Expense	188	0	$ 188	0
Share-based Payment Arrangement, Option [Member] \| Selling, General and Administrative Expenses [Member]
Share-based Payment Arrangement, Expense	598	0	$ 598	0
Restricted Stock [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 years 8 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value			$ 2,600
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	24,800		24,800
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent	900		900
Restricted Stock [Member] \| Research and Development Expense [Member]
Share-based Payment Arrangement, Expense	273	142	519	353
Restricted Stock [Member] \| Selling, General and Administrative Expenses [Member]
Share-based Payment Arrangement, Expense	$ 821	$ 500	$ 1,995	$ 1,122

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Gross number of share options (or share units) granted during the period.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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