Note 3 - Investment Securities - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Available for sale securities, amortized cost	$ 409,546	$ 363,433
Available for sale securities, gross unrealized gains	3,469	321
Available for sale securities, gross unrealized losses	(3,176)	(10,688)
Investment Securities Available for Sale, at Fair Value	409,839	353,066
US Government Agencies Debt Securities [Member]
Available for sale securities, amortized cost	403,165	356,498
Available for sale securities, gross unrealized gains	3,406	303
Available for sale securities, gross unrealized losses	(3,163)	(10,596)
Investment Securities Available for Sale, at Fair Value	403,408	346,205
US States and Political Subdivisions Debt Securities [Member]
Available for sale securities, amortized cost	3,511	4,008
Available for sale securities, gross unrealized gains	63	18
Available for sale securities, gross unrealized losses		(37)
Investment Securities Available for Sale, at Fair Value	3,574	3,989
Corporate Debt Securities [Member]
Available for sale securities, amortized cost	2,870	2,927
Available for sale securities, gross unrealized gains
Available for sale securities, gross unrealized losses	(13)	(55)
Investment Securities Available for Sale, at Fair Value	$ 2,857	$ 2,872

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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