Note 4 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Temporarily impaired securities, less than 12 months, fair value	$ 239,535	$ 69,967
Temporarily impaired securities, less than 12 months unrealized loss	5,131	498
Temporarily impaired securities, 12 months or more fair value	15,116	4,695
Temporarily impaired securities, 12 months or more unrealized loss	513	5
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	156,418	28,798
Temporarily impaired securities, less than 12 months unrealized loss	3,190	173
Temporarily impaired securities, 12 months or more fair value	944	0
Temporarily impaired securities, 12 months or more unrealized loss	53	0
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	71,912	32,353
Temporarily impaired securities, less than 12 months unrealized loss	1,868	249
Temporarily impaired securities, 12 months or more fair value	9,026	635
Temporarily impaired securities, 12 months or more unrealized loss	313	3
Commercial Mortgage Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	10,229	8,816
Temporarily impaired securities, less than 12 months unrealized loss	46	76
Temporarily impaired securities, 12 months or more fair value	5,146	4,060
Temporarily impaired securities, 12 months or more unrealized loss	147	$ 2
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	976
Temporarily impaired securities, less than 12 months unrealized loss	27
Temporarily impaired securities, 12 months or more fair value	0
Temporarily impaired securities, 12 months or more unrealized loss	$ 0