Note 4 - Loans - Troubled Debt Restructuring Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Charge-offs	$ (4,063)	$ 0	$ (305)
Accruing Troubled Debt Restructuring [Member]
Beginning balance	65,071	68,565	65,393
New restructurings	15,432	26,114	73,426
Restructured loans restored to accrual status	365	2,896	0
Charge-offs	(1,341)	0	0
Payments	(42,895)	(30,406)	(54,095)
Restructured loans placed on non-accrual	(1,296)	(2,098)	(13,919)
Expiration of loan concession	0	0	(2,240)
Ending balance	35,336	65,071	68,565
Non-accruing Troubled Debt Restructuring [Member]
Beginning balance	24,189	33,416	29,722
New restructurings	10,547	3,015	4,009
Restructured loans restored to accrual status	(365)	(2,896)	0
Charge-offs	(3,607)	(2,347)	(1,650)
Payments	(14,012)	(9,097)	(11,341)
Restructured loans placed on non-accrual	1,296	2,098	13,919
Foreclosures	0	0	(1,243)
Ending balance	$ 18,048	$ 24,189	$ 33,416