Note 5 - Loans - Troubled Debt Restructuring Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Charge-offs	$ (305)	$ (830)	$ (148)
Accruing Troubled Debt Restructuring [Member]
Beginning balance	65,393	81,680	104,356
New restructurings	73,426	26,965	17,752
Restructured loans restored to accrual status		10,303	723
Charge-offs		(88)	(104)
Payments	(54,095)	(24,192)	(30,858)
Restructured loans placed on non-accrual	(13,919)	(13,984)	(10,189)
Expiration of loan concession	(2,240)	(15,291)
Ending balance	68,565	65,393	81,680
Non-accruing Troubled Debt Restructuring [Member]
Beginning balance	29,722	39,923	41,618
New restructurings	4,009	6,940	2,006
Restructured loans restored to accrual status		(10,303)	(723)
Charge-offs	(1,650)	(5,271)	(3,246)
Payments	(11,341)	(15,551)	(9,921)
Restructured loans placed on non-accrual	13,919	13,984	10,189
Foreclosures	(1,243)
Ending balance	$ 33,416	$ 29,722	$ 39,923