Note 5 - Notes Payable and Long-term Debt - Summary of Credit Agreement and Line of Credit Note (Details) (Parentheticals) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	1.50%	1.50%
Promissory Note with BOKF [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 15,000,000	$ 15,000,000
Promissory Note with BOKF [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	1.50%	1.50%
Promissory Note and Business Loan Agreement with BOKF [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 6,000,000	$ 6,000,000