Note 12 - Equity Incentive Plans (Details Textual) - USD ($)								3 Months Ended	12 Months Ended
	Jun. 16, 2021	Jun. 15, 2021	Jul. 24, 2020	Jul. 20, 2020	Jul. 09, 2020	Jun. 15, 2020	Apr. 23, 2019	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 08, 2020	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)									10,216,106	6,813,033	1,811,652		865,163
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share)									$ 4.96	$ 2.70	$ 2.74		$ 8.13
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)									8 years 8 months 1 day
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value									$ 18,700,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares)									9,577,757
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price (in dollars per share)									$ 4.85
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term (Year)									8 years 7 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value									$ 18,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number (in shares)									3,743,237
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share)									$ 2.71
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Year)									7 years 7 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value									$ 14,200,000
Share Price (in dollars per share)									$ 6.27
Proceeds from Stock Options Exercised									$ 1,745,000	$ 602,000	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)									1,070,921	414,676	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value									$ 6,200,000	$ 2,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)									5,178,438	5,579,800	1,791,030
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)									$ 7.09	$ 2.66	$ 0.67
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate									0.00%	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)									$ 6.49	$ 2.49	$ 0.48
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount									$ 28,600,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)									3 years 25 days
Share-based Payment Arrangement, Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate									131.00%	111.00%	85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate									1.35%	0.88%	2.31%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year)									6 years 29 days	10 years	10 years
Chief Executive Officer [Member] | Performance-based Options [Member]
Share Price (in dollars per share)						$ 2.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)						900,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate						105.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate						0.35%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate						0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year)						5 years 2 months 23 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)						$ 0.31
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Grant Date Fair Value						$ 279,000
Chief Executive Officer [Member] | Performance-based Options [Member] | Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Minimum Closing Price for Ten Consecutive Trading Days (in dollars per share)					$ 5.00	$ 5.00
Chief Executive Officer [Member] | Performance-based Options [Member] | Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Minimum Closing Price for Ten Consecutive Trading Days (in dollars per share)				$ 7.50		$ 7.50
Chief Executive Officer [Member] | Performance-based Options [Member] | Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Minimum Closing Price for Ten Consecutive Trading Days (in dollars per share)			$ 10.00			$ 10.00
Chief Executive Officer [Member] | Performance-based Options and Time-based Options [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)						$ 2.46
Former Chairman of the Board [Member] | Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)		3 months
Former Chairman of the Board [Member] | Share-based Payment Arrangement, Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date	Jun. 16, 2023
Former Chairman of the Board [Member] | Stock Options with Accelerated Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Accelerated Vesting, Number (in shares)	100,000
Share-based Payment Arrangement, Plan Modification, Incremental Cost								$ 1,300,000
The 2019 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	16,900,000						1,600,000					8,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)							10 years