Note 4 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Temporarily impaired securities, less than 12 months, fair value	$ 525,094	$ 266,414
Temporarily impaired securities, less than 12 months unrealized loss	25,715	4,922
Temporarily impaired securities, 12 months or more fair value	114,273	51,999
Temporarily impaired securities, 12 months or more unrealized loss	14,880	2,145
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	964
Temporarily impaired securities, less than 12 months unrealized loss	25
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	238,220	201,650
Temporarily impaired securities, less than 12 months unrealized loss	14,294	3,530
Temporarily impaired securities, 12 months or more fair value	68,352	26,792
Temporarily impaired securities, 12 months or more unrealized loss	8,570	1,180
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	120,206	50,659
Temporarily impaired securities, less than 12 months unrealized loss	8,951	1,214
Temporarily impaired securities, 12 months or more fair value	36,298	20,542
Temporarily impaired securities, 12 months or more unrealized loss	5,850	793
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	160,387	13,139
Temporarily impaired securities, less than 12 months unrealized loss	2,262	141
Temporarily impaired securities, 12 months or more fair value	9,623	4,665
Temporarily impaired securities, 12 months or more unrealized loss	460	172
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	5,317	966
Temporarily impaired securities, less than 12 months unrealized loss	183	37
Temporarily impaired securities, 12 months or more fair value	0	0
Temporarily impaired securities, 12 months or more unrealized loss	$ 0	$ 0