Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018	Feb. 23, 2018
Outstanding Checks	$ 49,000
Accounts Receivable, Allowance for Credit Loss, Current	139,000			$ 139,000
Accounts Receivable, Credit Loss Expense (Reversal)	0	$ 33,000
Inventory Write-down	0
Deferred Rent Credit	115,000			$ 64,000
Asset Impairment Charges, Total	$ 127,000	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options and Warrants, Outstanding, Number	2,378,499	5,467,334
Share-based Compensation Arrangement by Share-based Payment Award, Options and Warrants, Outstanding, Aggregate Intrinsic Value	$ 351,000
Payments of Dividends, Total	$ 0
Operating Lease, Liability, Total			$ 1,900,000
Operating Lease, Right-of-Use Asset			1,900,000
Accounting Standards Update 2016-02 [Member]
Operating Lease, Liability, Total			1,900,000
Operating Lease, Right-of-Use Asset			$ 1,900,000
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Open Tax Year	2013 2014 2015 2016 2017
State and Local Jurisdiction [Member]
Open Tax Year	2014 2015 2016 2017 2018
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative, Notional Amount					$ 10,000,000
Derivative, Fixed Interest Rate					2.52%
Disposal Wells [Member]
Asset Impairment Charges, Total	$ 127,000
Minimum [Member]
Property, Plant and Equipment, Useful Life	5 years
Maximum [Member]
Property, Plant and Equipment, Useful Life	30 years