Note 12 - Federal and State Income Taxes - Significant Components of Deferred Tax Liabilities and Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax liabilities:
Property and equipment	$ 83,453	$ 78,502
Unrealized gains on securities	2,580	2,580
Prepaid expenses and other	2,193	2,667
Total deferred tax liabilities	88,226	83,749
Deferred tax assets:
Allowance for doubtful accounts	760	572
QAFMV tax credit carryforward	864	864
New hire tax credit	124	124
Compensated absences	512	460
Self-insurance allowances	5,630	188
Marketable equity securities	1,253	2,200
Net operating loss carryover	15,364	17,241
Other	198	203
Total deferred tax assets	24,705	21,852
Net deferred tax liability	$ 63,521	$ 61,897