Note 15 - Fair Value Measurements and Fair Values 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, 2019	Dec. 31, 2018	Dec. 31, 2017
Collateralized Debt Obligations [Member]
Balance		$ 489	$ 1,820
Security transferred to Level 3 measurement
Unrealized (losses) gains		237	1,006
Paydowns
Proceeds from sales		(660)	(1,539)
Realized losses		(66)	(798)
Impairment charges on Level 3
Balance			489
Corporate Debt Securities [Member]
Balance	3,069	3,086	2,971
Security transferred to Level 3 measurement
Unrealized (losses) gains	(249)	(17)	115
Paydowns
Proceeds from sales
Realized losses
Impairment charges on Level 3
Balance	$ 2,820	$ 3,069	$ 3,086