Note 7 - Investment and Equity Securities - Gross Unrealized Losses and Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Less than Twelve Months, Fair Value	$ 31,576	$ 7,264
Less than Twelve Months, Gross Unrealized Losses	(875)	(81)
Twelve Months or Greater, Fair Value	14,756	15,554
Twelve Months or Greater, Gross Unrealized Losses	(574)	(315)
Total, Fair Value	46,332	22,818
Total, Gross Unrealized Losses	(1,449)	(396)
US Government Agencies Debt Securities [Member]
Less than Twelve Months, Fair Value	548	557
Less than Twelve Months, Gross Unrealized Losses	(12)	(4)
Twelve Months or Greater, Fair Value	3,899	4,036
Twelve Months or Greater, Gross Unrealized Losses	(95)	(67)
Total, Fair Value	4,447	4,593
Total, Gross Unrealized Losses	(107)	(71)
Nontaxable Municipal Bonds [Member]
Less than Twelve Months, Fair Value	25,087	1,009
Less than Twelve Months, Gross Unrealized Losses	(660)	(6)
Twelve Months or Greater, Fair Value	2,721	2,784
Twelve Months or Greater, Gross Unrealized Losses	(94)	(32)
Total, Fair Value	27,808	3,793
Total, Gross Unrealized Losses	(754)	(38)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than Twelve Months, Fair Value	5,941	5,698
Less than Twelve Months, Gross Unrealized Losses	(203)	(71)
Twelve Months or Greater, Fair Value	8,136	8,734
Twelve Months or Greater, Gross Unrealized Losses	(385)	(216)
Total, Fair Value	14,077	14,432
Total, Gross Unrealized Losses	$ (588)	$ (287)