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Note 6 - Income Taxes (Details Textual) - USD ($) | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability |  |  | $ (56,500,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent | 21.00% | 21.00% | 35.00%
Deferred Income Tax Expense (Benefit), Excluding Effective Changes in Tax Rate |  |  | $ 8,000,000.0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Excluding Changes in Tax Rate, Percent |  |  | 40.10%
Unrecognized Tax Benefits, Ending Balance | $ 3,000,000.0 | $ 1,900,000 |
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions | 1,100,000 |  |
Unrecognized Tax Benefits that Would Impact Effective Tax Rate | 2,900,000 |  |
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total | $ 13,000 | $ 12,000 |
Domestic Tax Authority [Member] |  |  |
Open Tax Year | 2016 2017 2018 2019 |  |

X
- Definition Amount of deferred current income tax expense (benefit) and deferred income tax expense (benefit) excluding effective changes in tax rate pertaining to continuing operations. + References No definition available. + Details
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss), excluding changes in the tax rate. + References No definition available. + Details
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- Definition Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 + Details
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- Definition Tax year that remains open to examination under enacted tax laws, in CCYY format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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