Note 8 - Income Taxes (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 2,400,000		$ 2,400,000		$ 2,400,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	139,000		139,000		139,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0		0		$ 0
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	$ 405,000	$ 92,000	$ 467,000	$ 249,000
Domestic Tax Authority [Member]
Open Tax Year			2017 2018
State and Local Jurisdiction [Member]
Open Tax Year			2014 2015 2016 2017 2018