Note 3 - Income Taxes	3 Months Ended
Note 3 - Income Taxes	Mar. 31, 2020
Notes to Financial Statements
Income Tax Disclosure [Text Block]	3. Income Taxes Deferred tax assets and liabilities are determined based on differences between financial reporting and tax basis of assets and liabilities and are measured using the tax rates and laws expected to be in effect when the differences are expected to reverse. For the three months ended March 31, 2020, and 2019 , there was no income tax benefit due to net operating loss carryforwards ("NOLs") and we recorded a full valuation allowance against our net deferred taxes. At December 31, 2019 , we had, subject to the limitation discussed below, $245.2 million of pre- 2018 NOLs and $64.7 million of post 2017 NOL carryforwards for U.S. tax purposes. Our pre- 2018 NOLs will expire in varying amounts from 2022 through 2037, if not utilized; and can offset 100% of future taxable income. As a result of recent tax legislation, any NOLs arising in 2018, 2019, and 2020 can generally be carried back five years, carried forward indefinitely and can offset 100% of future taxable income for tax years before January 1, 2021 and up to 80% of future taxable income for tax years after December 31, 2020. Any NOLs arising after on or after January 1, 2021 can generally be carried forward indefinitely and can offset up to 80% of future taxable income for regular tax purposes. The use of our NOLs will be limited if there is an "ownership change" in our common stock, generally a cumulative ownership change exceeding 50% during a three year period, as determined under Section 382 of the Internal Revenue Code. As of March 31, 2020 , we have not had an ownership change as defined by Section 382. Given historical losses, uncertainties exist as to the future utilization of the NOL carryforwards. Therefore, we established a valuation allowance of $76.2 million for deferred tax assets at December 31, 2019 and for $67.4 million at March 31, 2020 . As of March 31, 2020 , we did not have any accrued interest or penalties related to uncertain tax positions. The tax years 2013 through 2019 remain open to examination by the tax jurisdictions to which we are subject. The Coronavirus Aid, Relief, and Economic Security Act ("CARES") that was enacted March 27, 2020 includes income tax provisions that allow NOL's to be carried back, allows interest expense to be deducted up to a higher percentage of adjusted taxable income, and modifies tax depreciation of qualified improvement property, among other provisions. These provisions have no material impact on the Company.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.