Note 2 - Investment Securities (Details Textual) xbrli-pure in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale, Unrealized Gain (Loss), Total		$ (9,000)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions	0
Fair Value, Inputs, Level 2 [Member]
Average Remaining Maturity of Investment	73 days
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	$ 4,274