Note 4 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Temporarily impaired securities, less than 12 months, fair value	$ 191,502	$ 69,967
Temporarily impaired securities, less than 12 months unrealized loss	8,805	498
Temporarily impaired securities, 12 months or more fair value	4,092	4,695
Temporarily impaired securities, 12 months or more unrealized loss	197	5
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	89,509	28,798
Temporarily impaired securities, less than 12 months unrealized loss	4,378	173
Temporarily impaired securities, 12 months or more fair value		0
Temporarily impaired securities, 12 months or more unrealized loss		0
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	89,706	32,353
Temporarily impaired securities, less than 12 months unrealized loss	4,198	249
Temporarily impaired securities, 12 months or more fair value	4,092	635
Temporarily impaired securities, 12 months or more unrealized loss	197	3
Commercial Mortgage Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	12,287	8,816
Temporarily impaired securities, less than 12 months unrealized loss	229	76
Temporarily impaired securities, 12 months or more fair value	0	4,060
Temporarily impaired securities, 12 months or more unrealized loss	$ 0	$ 2