Note 4 - Investments - Available for Sale and Held to Maturity Securities with Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Less Than Twelve Months, Fair Value	$ 18,627	$ 35,813
Less Than Twelve Months, Gross Unrealized Losses	351	417
Over Twelve Months, Fair Value		55,340
Over Twelve Months, Gross Unrealized Losses		256
Total, Fair Value	18,627	91,153
Total, Gross Unrealized Losses	351	673
Collateralized Mortgage Backed Securities [Member]
Less Than Twelve Months, Fair Value	7,755	10,941
Less Than Twelve Months, Gross Unrealized Losses	158	93
Over Twelve Months, Fair Value
Over Twelve Months, Gross Unrealized Losses
Total, Fair Value	7,755	10,941
Total, Gross Unrealized Losses	158	93
Collateralized Mortgage Obligations [Member]
Less Than Twelve Months, Fair Value	9,866	10,398
Less Than Twelve Months, Gross Unrealized Losses	163	203
Over Twelve Months, Fair Value
Over Twelve Months, Gross Unrealized Losses
Total, Fair Value	9,866	10,398
Total, Gross Unrealized Losses	163	203
US States and Political Subdivisions Debt Securities [Member]
Less Than Twelve Months, Fair Value	1,006	4,602
Less Than Twelve Months, Gross Unrealized Losses	30	61
Over Twelve Months, Fair Value		608
Over Twelve Months, Gross Unrealized Losses		5
Total, Fair Value	1,006	5,210
Total, Gross Unrealized Losses	$ 30	66
US Treasury Securities [Member]
Less Than Twelve Months, Fair Value		4,894
Less Than Twelve Months, Gross Unrealized Losses		44
Over Twelve Months, Fair Value		49,753
Over Twelve Months, Gross Unrealized Losses		231
Total, Fair Value		54,647
Total, Gross Unrealized Losses		275
US Government Agencies Debt Securities [Member]
Less Than Twelve Months, Fair Value		4,978
Less Than Twelve Months, Gross Unrealized Losses		16
Over Twelve Months, Fair Value		4,979
Over Twelve Months, Gross Unrealized Losses		20
Total, Fair Value		9,957
Total, Gross Unrealized Losses		$ 36