Note 8 - Commitments and Contingencies (Details Textual)		3 Months Ended		12 Months Ended
	Dec. 08, 2015	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
SBS Rodgers Litigation [Member]
Loss Contingency, Number of Plaintiffs	61
Loss Contingency, Number of Plaintiffs Not Challenged by Defendant	11
SBS [Member]
Related Party Transaction, Reimbursement of Legal Expenses from Transaction with Related Party		$ 60,000	$ 85,000
Domestic Merchandising Specialists Field Force [Member] | SBS [Member]
Percent Of Service Provided By Related Party		52.00%	83.00%	77.00%
Payments for Related Party Services		$ 6,800,000	$ 5,900,000	$ 25,900,000