Note 6 - Leases (Details Textual) $ in Thousands	Mar. 06, 2019 USD ($) a	Dec. 31, 2019 USD ($) ft²	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 31, 2017 a
Operating Lease, Liability, Total		$ 701
Operating Lease, Right-of-Use Asset		$ 1,054
Accounting Standards Update 2016-02 [Member]
Operating Lease, Liability, Total			$ 1,900
Operating Lease, Right-of-Use Asset			1,600
Deferred Rent Credit			(100)
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 200	$ (213)
City of Texas City and the State of Texas [Member]
Area Available for Lease | a					994
Lessee, Operating Lease, Term of Contract		3 years
Lessee, Operating Lease, Renewal Term		1 year
BND [Member]
Area Available for Lease | a	984
Lessee, Operating Lease, Term of Contract	30 years
Lessee, Operating Lease, Renewal Term	10 years
Lessee, Operating Lease, Number of Consecutive Renewal Term	2
Operating Lease, Liability, Total	$ 2,300
Operating Lease, Right-of-Use Asset	$ 2,300
Houston, Texas [Member]
Area of Real Estate Property | ft²		38,300