Note 7 - Derivatives and Hedging Activities - Hedged Interest Rate Swaps and Non-hedged Interest Rate Swaps (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Swapped loan portfolio loan-to-value percentage, including the potential swap exposure	65.00%
Interest rate swap
Derivative [Line Items]
Interest rate swaps collateralized by investment securities	$ 228,925	$ 224,930
Interest rate swap | Cash
Derivative [Line Items]
Interest rate swaps collateralized by investment securities	21,100	45,719
Interest rate swap | U.S. govt. sponsored agency securities.
Derivative [Line Items]
Interest rate swaps collateralized by investment securities	3,555	3,628
Interest rate swap | Municipal securities
Derivative [Line Items]
Interest rate swaps collateralized by investment securities	65,104	85,937
Interest rate swap | Residential mortgage-backed and related securities
Derivative [Line Items]
Interest rate swaps collateralized by investment securities	$ 139,166	$ 89,646