Note 2 - Investment Securities - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available for sale securities, amortized cost	$ 333,656	$ 362,465
Available for sale securities, gross unrealized gains	56	293
Available for sale securities, gross unrealized losses	(15,680)	(8,511)
Investment Securities Available for Sale, at Fair Value	318,032	354,247
US Government Agencies Debt Securities [Member]
Available for sale securities, amortized cost	326,676	354,931
Available for sale securities, gross unrealized gains	52	258
Available for sale securities, gross unrealized losses	(15,550)	(8,466)
Investment Securities Available for Sale, at Fair Value	311,178	346,723
US States and Political Subdivisions Debt Securities [Member]
Available for sale securities, amortized cost	4,024	4,493
Available for sale securities, gross unrealized gains	4	23
Available for sale securities, gross unrealized losses	(56)	(23)
Investment Securities Available for Sale, at Fair Value	3,972	4,493
Corporate Debt Securities [Member]
Available for sale securities, amortized cost	2,956	2,048
Available for sale securities, gross unrealized gains		12
Available for sale securities, gross unrealized losses	(74)
Investment Securities Available for Sale, at Fair Value	$ 2,882	2,060
Asset-backed Securities [Member]
Available for sale securities, amortized cost		993
Available for sale securities, gross unrealized gains
Available for sale securities, gross unrealized losses		(22)
Investment Securities Available for Sale, at Fair Value		$ 971

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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