Note 8 - Income Taxes - Reconciliation of Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax (expense) benefit at U.S. Statutory rates	$ (12,142)	$ (5,602)	$ 33,732
(Increase) decrease in deferred tax asset valuation allowance	13,135	57,309	(34,072)
Permanent differences	(500)	(1,134)	(1,133)
Return to provision estimated revision	(470)	2,494	1,473
Change in deferred tax rate		(53,125)
Other	$ (23)	$ 58