Note 7 - Investment and Equity Securities - Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Less than Twelve Months, Fair Value	$ 51,663	$ 5,733
Less than Twelve Months, Gross Unrealized Losses	(3,824)	(27)
Twelve Months or Greater, Fair Value	2,539	8,223
Twelve Months or Greater, Gross Unrealized Losses	(14)	(107)
Total, Fair Value	54,202	13,956
Total, Gross Unrealized Losses	(3,838)	(134)
Nontaxable Municipal Bonds [Member]
Less than Twelve Months, Fair Value	51,663	4,324
Less than Twelve Months, Gross Unrealized Losses	(3,824)	(25)
Twelve Months or Greater, Fair Value
Twelve Months or Greater, Gross Unrealized Losses
Total, Fair Value	51,663	4,324
Total, Gross Unrealized Losses	(3,824)	(25)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than Twelve Months, Fair Value		1,409
Less than Twelve Months, Gross Unrealized Losses		(2)
Twelve Months or Greater, Fair Value	2,539	8,223
Twelve Months or Greater, Gross Unrealized Losses	(14)	(107)
Total, Fair Value	2,539	9,632
Total, Gross Unrealized Losses	$ (14)	$ (109)