Note 4 - Fair Values of Financial Instruments - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Reported Value Measurement [Member]
Financial Assets:
Cash and cash equivalents	$ 6,951	$ 5,934
Accounts receivable	10,729	7,165
U. S. agency securities		5,200
Financial liabilities:
Accounts payable	(16,393)	(19,533)
Term loan	(9,474)
Financed insurance payable	(287)
Estimate of Fair Value Measurement [Member]
Financial Assets:
Cash and cash equivalents	6,951	5,934
Accounts receivable	10,729	7,165
U. S. agency securities		5,196
Financial liabilities:
Accounts payable	(16,393)	(19,533)
Term loan	(9,474)
Financed insurance payable	$ (287)