Note 12 - Derivatives and Risk Management Activities - Derivative Instrument Gain (Loss) Recorded in Statement of Income (Details) - Mortgage Banking Income [Member] - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Best Efforts Forward Loan sales Commitments [Member] | Liability Derivatives [Member]
Derivative Gain (Loss), Net	$ 100	$ 81	$ (421)	$ 12
Mandatory Forward Loan Sales Commitments [Member] | Liability Derivatives [Member]
Derivative Gain (Loss), Net	(199)	148	(442)	151
Asset Derivatives [Member] | Best Efforts Forward Loan sales Commitments [Member]
Derivative Gain (Loss), Net	(8)	26	(4)	38
Asset Derivatives [Member] | Mandatory Forward Loan Sales Commitments [Member]
Derivative Gain (Loss), Net	0	27	(2)	17
Interest Rate Lock Commitments [Member] | Liability Derivatives [Member]
Derivative Gain (Loss), Net	(1)	(2)	(1)	(2)
Interest Rate Lock Commitments [Member] | Asset Derivatives [Member]
Derivative Gain (Loss), Net	$ (191)	$ (201)	$ 1,089	$ 96