Note 10 - Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Computed "expected" income tax expense	$ (3,554)	$ 1,642	$ 11,745
State income taxes, net of federal income tax effect	(227)	(600)	2,484
831(b) election	(123)	(393)	(200)
Per diem allowances	1,028	1,450	1,446
Tax contingency accruals	65	601	(57)
Valuation allowance, net	(139)	321	0
Tax credits	(403)	(377)	(968)
Excess tax benefits on share-based compensation	129	105	50
Change in prior year estimates	288	(420)	0
Other, net	132	20	444
Income tax (benefit) expense	$ (2,804)	$ 2,349	$ 14,944