Note 6 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Less than 12 months, fair value	$ 118,916	$ 42,702
Less than 12 months, gross unrealized losses	2,036	364
12 months or greater, fair value	97,987	87,854
12 months or greater, gross unrealized losses	3,063	2,144
Total, fair value	216,903	130,556
Total, gross unrealized losses	5,099	2,508
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value	4,399	4,136
Less than 12 months, gross unrealized losses	28	56
12 months or greater, fair value	4,610	2,004
12 months or greater, gross unrealized losses	116	12
Total, fair value	9,009	6,140
Total, gross unrealized losses	144	68
Corporate Debt Securities [Member]
Less than 12 months, fair value	6,274	4,448
Less than 12 months, gross unrealized losses	260	69
12 months or greater, fair value	2,324	2,007
12 months or greater, gross unrealized losses	176	23
Total, fair value	8,598	6,455
Total, gross unrealized losses	436	92
Collateralized Mortgage Backed Securities [Member]
Less than 12 months, fair value	67,770	8,320
Less than 12 months, gross unrealized losses	1,264	71
12 months or greater, fair value	61,271	71,182
12 months or greater, gross unrealized losses	2,300	1,753
Total, fair value	129,041	79,502
Total, gross unrealized losses	3,564	1,824
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	40,473	25,798
Less than 12 months, gross unrealized losses	484	168
12 months or greater, fair value	29,782	11,927
12 months or greater, gross unrealized losses	471	259
Total, fair value	70,255	37,725
Total, gross unrealized losses	955	427
Other Debt Obligations [Member]
Less than 12 months, fair value	0	0
Less than 12 months, gross unrealized losses	0	0
12 months or greater, fair value		734
12 months or greater, gross unrealized losses		97
Total, fair value		734
Total, gross unrealized losses		$ 97