Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
Deferred Tax Liabilities, Net, Total	$ 80,330	$ 77,467
Deferred Tax Assets, Valuation Allowance, Total	385	63
Liability for Uncertainty in Income Taxes, Current	900	2,700
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	100	900
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	800	100	$ 100
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	900	$ 2,500
Charitable Contributions Carryforward	2,100
Alternative Minimum Tax Credit Carry Forward [Member]
Tax Credit Carryforward, Amount	1,200
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	115,700
Tax Credit Carryforward, Amount	600
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	103,900
Operating Loss Carryforwards, Subject to Expiration	1,400
Operating Loss Carryforwards, Not Subject to Expiration	102,500
Tax Credit Carryforward, Amount	10,400
Deferred Tax Assets Related to State Net Operating Loss Carry Forwards [Member] | State and Local Jurisdiction [Member]
Deferred Tax Assets, Valuation Allowance, Total	$ 400