Note 7 - Commitments and Contingencies (Details Textual) - USD ($)					3 Months Ended	12 Months Ended
	Apr. 11, 2018	Jul. 01, 2017	Apr. 01, 2014	Mar. 28, 2014	Dec. 31, 2018	Dec. 31, 2016	Mar. 31, 2019	Feb. 04, 2014	Dec. 31, 2013
Operating Lease, Right-of-Use Asset							$ 3,200,000
Operating Lease, Liability, Total							$ 3,576,000
Derivative Liability, Total								$ 5,000,000
Shareholder Derivative Suit [Member]
Litigation Settlement, Amount Awarded to Other Party				$ 5,000,000
Accrued Liabilities and Other Liabilities, Total									$ 2,500,000
Litigation Settlement Fees and Costs			$ 2,500,000
Partial Indemnification, Individual Defendants Paid	$ 2,500,000					$ 2,500,000
Litigation Settlement, Monthly Payments		$ 25,000
Insurance-related Litigation [Member]
Gain (Loss) Related to Litigation Settlement, Total					$ 6,000,000