Note 5 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Less than 12 months, fair value	$ 489,447	$ 68,096
Less than 12 months, gross unrealized losses	4,012	357
12 months or greater, fair value	18,198	17
12 months or greater, gross unrealized losses	255	1
Total, fair value	507,645	68,113
Total, gross unrealized losses	4,267	358
US Treasury Securities [Member]
Less than 12 months, fair value	22,627
Less than 12 months, gross unrealized losses	135
12 months or greater, fair value	0
12 months or greater, gross unrealized losses	0
Total, fair value	22,627
Total, gross unrealized losses	135
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value	25,320	0
Less than 12 months, gross unrealized losses	53	0
12 months or greater, fair value	0	0
12 months or greater, gross unrealized losses	0	0
Total, fair value	25,320	0
Total, gross unrealized losses	53	0
Corporate Debt Securities [Member]
Less than 12 months, fair value	4,395	4,995
Less than 12 months, gross unrealized losses	45	5
12 months or greater, fair value	0	0
12 months or greater, gross unrealized losses	0	0
Total, fair value	4,395	4,995
Total, gross unrealized losses	45	5
Collateralized Mortgage Backed Securities [Member]
Less than 12 months, fair value	323,885	44,680
Less than 12 months, gross unrealized losses	2,741	246
12 months or greater, fair value	12,400	17
12 months or greater, gross unrealized losses	96	1
Total, fair value	336,285	44,697
Total, gross unrealized losses	2,837	247
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	113,220	18,421
Less than 12 months, gross unrealized losses	1,038	106
12 months or greater, fair value	5,798	0
12 months or greater, gross unrealized losses	159	0
Total, fair value	119,018	18,421
Total, gross unrealized losses	1,197	106
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	0	0
12 months or greater, gross unrealized losses	0	0
Total, fair value	0	0
Total, gross unrealized losses	$ 0	$ 0