Note 15 - Fair Value Measurements and Fair Value of Financial Instruments - Assets Measured on a Recurring Basis Using Significant Unobservable Inputs (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collateralized Debt Obligations [Member]
Balance	$ 489	$ 1,820	$ 1,883
Security transferred to Level 3 measurement
Unrealized (losses) gains	237	1,006	(56)
Paydowns
Proceeds from sales	(660)	(1,539)
Realized losses	(66)	(798)
Impairment charges on Level 3			(7)
Balance		489	1,820
Corporate Debt Securities [Member]
Balance	3,086	2,971	2,834
Security transferred to Level 3 measurement
Unrealized (losses) gains	(17)	115	137
Paydowns
Proceeds from sales
Realized losses
Impairment charges on Level 3
Balance	$ 3,069	$ 3,086	$ 2,971