Note 7 - Investment Securities - Amortized Costs and Estimated Fair Value of the Securities Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available for Sale Securities - Amortized Cost	$ 411,995	$ 427,831
Available for Sale Securities - Gross Unrealized Gains	670	1,181
Available for Sale Securities - Gross Unrealized Losses	10,377	5,694
Available for Sale Securities - Estimated Fair Value	402,288	423,318
Held to Maturity Securities - Amortized Cost	3,350	3,364
Held to Maturity Securities - Estimated Fair Value	3,424	3,478
US Government-sponsored Enterprises Debt Securities [Member]
Available for Sale Securities - Amortized Cost	42,633	43,601
Available for Sale Securities - Gross Unrealized Gains	14	44
Available for Sale Securities - Gross Unrealized Losses	691	437
Available for Sale Securities - Estimated Fair Value	41,956	43,208
US States and Political Subdivisions Debt Securities [Member]
Available for Sale Securities - Amortized Cost	109,652	114,960
Available for Sale Securities - Gross Unrealized Gains	281	562
Available for Sale Securities - Gross Unrealized Losses	2,365	1,273
Available for Sale Securities - Estimated Fair Value	107,568	114,249
Held to Maturity Securities - Amortized Cost	3,350	3,364
Held to Maturity Securities - Gross Unrealized Gains	74	114
Held to Maturity Securities - Gross Unrealized Losses	0	0
Held to Maturity Securities - Estimated Fair Value	3,424	3,478
Residential Mortgage Backed Securities [Member]
Available for Sale Securities - Amortized Cost	186,441	195,605
Available for Sale Securities - Gross Unrealized Gains	318	523
Available for Sale Securities - Gross Unrealized Losses	5,158	2,735
Available for Sale Securities - Estimated Fair Value	181,601	193,393
Commercial Mortgage Backed Securities [Member]
Available for Sale Securities - Amortized Cost	49,990	50,518
Available for Sale Securities - Gross Unrealized Gains		42
Available for Sale Securities - Gross Unrealized Losses	2,116	1,208
Available for Sale Securities - Estimated Fair Value	47,874	49,352
Asset-backed Securities [Member]
Available for Sale Securities - Amortized Cost	15,538	15,569
Available for Sale Securities - Gross Unrealized Gains	8	9
Available for Sale Securities - Gross Unrealized Losses	29	4
Available for Sale Securities - Estimated Fair Value	15,517	15,574
Corporate Debt Securities [Member]
Available for Sale Securities - Amortized Cost	7,741	7,578
Available for Sale Securities - Gross Unrealized Gains	49	1
Available for Sale Securities - Gross Unrealized Losses	18	37
Available for Sale Securities - Estimated Fair Value	$ 7,772	$ 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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