Note 6 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Less than 12 months, fair value	$ 4,384	$ 118,916
Less than 12 months, gross unrealized losses	28	2,036
12 months or greater, fair value	51,987	97,987
12 months or greater, gross unrealized losses	652	3,063
Total, fair value	56,371	216,903
Total, gross unrealized losses	680	5,099
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value	2,486	4,399
Less than 12 months, gross unrealized losses	20	28
12 months or greater, fair value		4,610
12 months or greater, gross unrealized losses		116
Total, fair value	2,486	9,009
Total, gross unrealized losses	20	144
Corporate Debt Securities [Member]
Less than 12 months, fair value		6,274
Less than 12 months, gross unrealized losses		260
12 months or greater, fair value	6,360	2,324
12 months or greater, gross unrealized losses	158	176
Total, fair value	6,360	8,598
Total, gross unrealized losses	158	436
Collateralized Mortgage Backed Securities [Member]
Less than 12 months, fair value	950	67,770
Less than 12 months, gross unrealized losses	4	1,264
12 months or greater, fair value	44,366	61,271
12 months or greater, gross unrealized losses	493	2,300
Total, fair value	45,316	129,041
Total, gross unrealized losses	497	3,564
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	948	40,473
Less than 12 months, gross unrealized losses	4	484
12 months or greater, fair value	1,261	29,782
12 months or greater, gross unrealized losses	1	471
Total, fair value	2,209	70,255
Total, gross unrealized losses	$ 5	$ 955