Note 6 - Leases (Details Textual) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019
Operating Lease, Weighted Average Remaining Lease Term	27 months	29 months
Operating Lease, Weighted Average Discount Rate, Percent	2.25%	2.10%
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 82,000
Operating Lease, Payments	306,000
Other Operating Income (Expense) [Member]
Operating Lease, Cost	848,000
Short-term Lease, Cost	$ 542,000
Minimum [Member]
Lessee, Operating Lease, Renewal Term	6 months
Maximum [Member]
Lessee, Operating Lease, Renewal Term	3 years