Note 4 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Temporarily impaired securities, less than 12 months, fair value	$ 554,162	$ 266,414
Temporarily impaired securities, less than 12 months unrealized loss	48,867	4,922
Temporarily impaired securities, 12 months or more fair value	106,949	51,999
Temporarily impaired securities, 12 months or more unrealized loss	22,130	2,145
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	955
Temporarily impaired securities, less than 12 months unrealized loss	35
Temporarily impaired securities, 12 months or more fair value	0
Temporarily impaired securities, 12 months or more unrealized loss	0
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	262,561	201,650
Temporarily impaired securities, less than 12 months unrealized loss	22,913	3,530
Temporarily impaired securities, 12 months or more fair value	64,695	26,792
Temporarily impaired securities, 12 months or more unrealized loss	12,228	1,180
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	120,556	50,659
Temporarily impaired securities, less than 12 months unrealized loss	20,031	1,214
Temporarily impaired securities, 12 months or more fair value	32,812	20,542
Temporarily impaired securities, 12 months or more unrealized loss	9,310	793
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	164,176	13,139
Temporarily impaired securities, less than 12 months unrealized loss	5,302	141
Temporarily impaired securities, 12 months or more fair value	9,442	4,665
Temporarily impaired securities, 12 months or more unrealized loss	592	172
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	5,914	966
Temporarily impaired securities, less than 12 months unrealized loss	586	37
Temporarily impaired securities, 12 months or more fair value	0	0
Temporarily impaired securities, 12 months or more unrealized loss	$ 0	$ 0