Note 14 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Expense (Benefit), Total	$ (9,937)	$ (664)
Income Tax Expense (Benefit), Discrete Tax Items	8,100	300
Income Tax Expense (Benefit), Exploration Abandonment	5,800
Exploration Abandonment and Impairment Expense	14,036	$ 5
Income Tax Expense (Benefit), Change in Tax Law	$ (2,100)