Note 5 - Common Stock Options (Details Textual) - The Plan [Member] $ in Millions |
6 Months Ended |
---|---|
Jun. 30, 2019
USD ($)
| |
Any One Person [Member] | |
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum | 5.00% |
Share-based Payment Arrangement, Option [Member] | |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period | 10 years |
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount | $ 4.9 |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition | 1 year 204 days |