Note 7 - Investment Securities - Amortized Costs and Estimated Fair Value of the Securities Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available for Sale Securities - Amortized Cost	$ 391,093	$ 427,831
Available for Sale Securities - Gross Unrealized Gains	564	1,181
Available for Sale Securities - Gross Unrealized Losses	11,678	5,694
Available for Sale Securities - Estimated Fair Value	379,979	423,318
Held to Maturity Securities - Amortized Cost	2,837	3,364
Held to Maturity Securities - Estimated Fair Value	2,868	3,478
US Government-sponsored Enterprises Debt Securities [Member]
Available for Sale Securities - Amortized Cost	34,676	43,601
Available for Sale Securities - Gross Unrealized Gains	5	44
Available for Sale Securities - Gross Unrealized Losses	857	437
Available for Sale Securities - Estimated Fair Value	33,824	43,208
US States and Political Subdivisions Debt Securities [Member]
Available for Sale Securities - Amortized Cost	105,616	114,960
Available for Sale Securities - Gross Unrealized Gains	263	562
Available for Sale Securities - Gross Unrealized Losses	2,450	1,273
Available for Sale Securities - Estimated Fair Value	103,429	114,249
Held to Maturity Securities - Amortized Cost	2,837	3,364
Held to Maturity Securities - Gross Unrealized Gains	31	114
Held to Maturity Securities - Gross Unrealized Losses	0	0
Held to Maturity Securities - Estimated Fair Value	2,868	3,478
Residential Mortgage Backed Securities [Member]
Available for Sale Securities - Amortized Cost	178,426	195,605
Available for Sale Securities - Gross Unrealized Gains	242	523
Available for Sale Securities - Gross Unrealized Losses	5,830	2,735
Available for Sale Securities - Estimated Fair Value	172,838	193,393
Commercial Mortgage Backed Securities [Member]
Available for Sale Securities - Amortized Cost	49,387	50,518
Available for Sale Securities - Gross Unrealized Gains		42
Available for Sale Securities - Gross Unrealized Losses	2,478	1,208
Available for Sale Securities - Estimated Fair Value	46,909	49,352
Asset-backed Securities [Member]
Available for Sale Securities - Amortized Cost	15,493	15,569
Available for Sale Securities - Gross Unrealized Gains	32	9
Available for Sale Securities - Gross Unrealized Losses	26	4
Available for Sale Securities - Estimated Fair Value	15,499	15,574
Corporate Debt Securities [Member]
Available for Sale Securities - Amortized Cost	7,495	7,578
Available for Sale Securities - Gross Unrealized Gains	22	1
Available for Sale Securities - Gross Unrealized Losses	37	37
Available for Sale Securities - Estimated Fair Value	$ 7,480	$ 7,542

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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