Note 3 - Securities - Available-for-sale Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
One year or less, amortized cost	$ 1,734
One year or less, fair value	1,731
After one year through five years, amortized cost	56,360
After one year through five years, fair value	56,370
After five years through ten years, amortized cost	77,470
After five years through ten years, fair value	77,490
After ten years, amortized cost	4,029
After ten years, fair value	3,949
Total, amortized cost	275,365	$ 301,779
Available-for-sale debt securities	274,114	296,032
Collateralized Mortgage Obligations [Member]
Securities without a single maturity, amortized cost	113,095
Securities without a single maturity, fair value	111,902
Collateralized Mortgage Backed Securities [Member]
Securities without a single maturity, amortized cost	21,104
Securities without a single maturity, fair value	21,112
Total, amortized cost	21,104	24,165
Available-for-sale debt securities	21,112	23,934
Asset-backed Securities [Member]
Securities without a single maturity, amortized cost	1,573
Securities without a single maturity, fair value	1,560
Total, amortized cost	1,573	1,825
Available-for-sale debt securities	$ 1,560	$ 1,802