Note 8 - Stock-based Compensation (Details Textual) - USD ($) | 1 Months Ended | 2 Months Ended | 6 Months Ended | |
Jun. 30, 2018 | Apr. 30, 2018 | Mar. 31, 2018 | Jun. 30, 2018 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance | 25,165,306 | | | 25,165,306 | 25,165,306 | | 30,375,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period | | | | | 5,098,915 | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | | | | | 765,779 | | |
Proceeds from Stock Options Exercised | | | | | $ 77,000 | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | | | | | 655,000 | | |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price | | | | | $ 1.31 | | |
Allocated Share-based Compensation Expense, Total | | | | | $ 5,700,000 | $ 5,000,000 | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $ 24,200,000 | | | $ 24,200,000 | 24,200,000 | | |
Employee Stock Option [Member] | | | | | | | |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total | $ 1,280,000 | | | $ 1,280,000 | $ 1,280,000 | | |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition | | | | | 1 year 109 days | | |
Equity Incentive Plan 2017 [Member] | Employee Stock Option [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term | | 5 years 273 days | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate | | 62.00% | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate | | 2.78% | | | | | |
Mr. Monfort [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance | 14,297,902 | | | 14,297,902 | 14,297,902 | | |
Certain Non-Employees [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period | 499,123 | | 297,694 | | | | |
Stock Issued During Period, Value, Share-based Compensation, Forfeited | | | $ 423,308 | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | | | | 765,779 | | | |
Proceeds from Stock Options Exercised | | | | $ 76,578 | | | |
One Non-employee [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Extended in Period | 207,968 | | | | | | |
Certain Employees and Directors [Member] | Equity Incentive Plan 2017 [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | | 655,000 | | | | | |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price | | $ 1.31 | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Fair Market Value | | $ 229,643 | | | | | |
Certain Employees and Directors [Member] | Equity Incentive Plan 2017 [Member] | Employee Stock Option [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | | 3 years | | | | | |
Certain Employees and Directors [Member] | Plan 2012 [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period | 3,450,000 | | | | | | |
Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price | $ 10.49 | | | | | | |