Note 5 - Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 12,427	$ 8,987	$ 9,280
State	990	1,125	946
Total current	13,417	10,112	10,226
Deferred:
Federal	(48,424)	12,427	13,042
State	1,196	1,063	1,678
Total deferred	(47,228)	13,490	14,720
Total (benefit) expense	$ (33,811)	$ 23,602	$ 24,946