Note 11 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended | |
Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2022 | Jun. 30, 2021 | Dec. 31, 2021 | Jun. 01, 2021 |
Common Stock, No Par Value (in dollars per share) | $ 0 | | $ 0 | | $ 0 | |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year) | | | 10 years | | | |
Employee Stock Purchase Plan, Maximum Payroll Deduction, Percent | 15% | | 15% | | | |
Employee Stock Purchase Plan, Stock Purchase Price, Percent | 85% | | 85% | | | |
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares) | | | 0 | | 0 | |
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount | $ 5,480 | | $ 5,480 | | | |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | | | 1 year 7 months 6 days | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number (in shares) | 10,656,000 | 8,001,000 | 10,656,000 | 8,001,000 | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share) | $ 4.65 | $ 4.60 | $ 4.65 | $ 4.60 | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Year) | | | 4 years 9 months 18 days | 5 years 8 months 12 days | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term (Year) | | | 6 years 4 months 24 days | 6 years 9 months 18 days | | |
Share-Based Payment Arrangement, Expense | $ 779 | $ 2,164 | $ 3,293 | $ 8,807 | | |
Officer [Member] | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number (in shares) | 851,053 | 1,679,169 | 851,053 | 1,679,169 | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Year) | | | | 12 months | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term (Year) | | | 12 years | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term (Month) | | | | 12 months | | |
Officer [Member] | Continuing Vesting Options with No Service Requirement [Member] | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Accelerated Vesting, Number (in shares) | | | 477,166 | 504,833 | | |
Officer [Member] | Vested Options [Member] | | | | | | |
Share-Based Payment Arrangement, Expense | | | $ 67 | | | |
Officer [Member] | Unvested Options [Member] | | | | | | |
Share-Based Payment Arrangement, Expense | | | | $ 1,600 | | |
Maximum [Member] | Officer [Member] | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share) | $ 6.91 | $ 7.44 | $ 6.91 | $ 7.44 | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Year) | | | 12 years | | | |
Minimum [Member] | Officer [Member] | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price (in dollars per share) | $ 1.34 | $ 1.03 | $ 1.34 | $ 1.03 | | |
New Incentive Plan [Member] | | | | | | |
Common Stock, No Par Value (in dollars per share) | | | | | | $ 0 |
New Incentive Plan [Member] | Maximum [Member] | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares) | | | | | | 9,343,242 |
ESPP [Member] | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares) | 1,700,000 | | 1,700,000 | | | |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | | | 1 year | | | |
Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount | $ 3 | | $ 3 | | | |