Note 2 - Investment Securities (Details Textual) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Available-for-Sale, Securities in Unrealized Loss Positions, Depreciation from Amortized Cost Percentage		0.90%		0.90%
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Total				$ 0
Debt Securities, Available-for-sale, Realized Loss		$ 0	$ 307,000	86,000	$ 313,000
Debt Securities, Time Deposits, Realized Loss				11,000
Debt Securities, Available-for-sale, Realized Gain		0	$ 211,000		$ 218,000
Investment, Number of Shares Acquired	90,000
Investment Ownership Percentage	5.00%
Payments to Acquire Other Investments	$ 1,900,000
Equity Securities, FV-NI, Unrealized Loss		14,000
Equity Securities, FV-NI, Unrealized Gain				117,000
Equity Securities, FV-NI		$ 1,800,000		$ 1,800,000		$ 1,700,000