Note 5 - Investment Securities - Unrealized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investment securities available for sale, at amortized cost	$ 372,014	$ 380,396
Investment securities available for sale, gross unrealized gains	476	336
Investment securities available for sale, gross unrealized losses	(10,162)	(10,993)
Investment securities available for sale, at fair value	362,328	369,739
Investment securities held to maturity, at amortized cost	421,850	432,499
Investment securities held to maturity, gross unrealized gains	675	802
Investment securities held to maturity, gross unrealized losses	(8,826)	(8,118)
Investment securities held to maturity, at fair value	413,699	425,183
Investment securities held to maturity, at amortized cost	421,850	432,499
Investment securities held to maturity, gross unrealized losses	(8,826)	(8,118)
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, at amortized cost	222,278	230,252
Investment securities available for sale, gross unrealized gains	99	145
Investment securities available for sale, gross unrealized losses	(4,761)	(5,632)
Investment securities available for sale, at fair value	217,616	224,765
Investment securities held to maturity, at amortized cost	196,461	202,990
Investment securities held to maturity, gross unrealized gains	644	793
Investment securities held to maturity, gross unrealized losses	(2,788)	(2,553)
Investment securities held to maturity, at fair value	194,317	201,230
Investment securities held to maturity, at amortized cost	196,461	202,990
Investment securities held to maturity, gross unrealized losses	(2,788)	(2,553)
Collateralized Mortgage Backed Securities [Member]
Investment securities available for sale, at amortized cost	37,273	37,973
Investment securities available for sale, gross unrealized gains	24	32
Investment securities available for sale, gross unrealized losses	(1,267)	(1,295)
Investment securities available for sale, at fair value	36,030	36,710
Investment securities held to maturity, at amortized cost	127,192	129,951
Investment securities held to maturity, gross unrealized gains		1
Investment securities held to maturity, gross unrealized losses	(3,608)	(3,327)
Investment securities held to maturity, at fair value	123,584	126,625
Investment securities held to maturity, at amortized cost	127,192	129,951
Investment securities held to maturity, gross unrealized losses	(3,608)	(3,327)
US States and Political Subdivisions Debt Securities [Member]
Investment securities available for sale, at amortized cost	27,727	26,825
Investment securities available for sale, gross unrealized gains	255	151
Investment securities available for sale, gross unrealized losses	(342)	(429)
Investment securities available for sale, at fair value	27,640	26,547
Corporate Debt Securities [Member]
Investment securities available for sale, at amortized cost	66,698	66,718
Investment securities available for sale, gross unrealized gains	98	8
Investment securities available for sale, gross unrealized losses	(2,515)	(1,978)
Investment securities available for sale, at fair value	64,281	64,748
Asset-backed Securities [Member]
Investment securities available for sale, at amortized cost	14,975	15,565
Investment securities available for sale, gross unrealized gains
Investment securities available for sale, gross unrealized losses	(175)	(416)
Investment securities available for sale, at fair value	14,800	15,149
Collateralized Debt Obligations [Member]
Investment securities available for sale, at amortized cost	3,063	3,063
Investment securities available for sale, gross unrealized gains
Investment securities available for sale, gross unrealized losses	(1,102)	(1,243)
Investment securities available for sale, at fair value	1,961	1,820
US Government Agencies Debt Securities [Member]
Investment securities held to maturity, at amortized cost	97,177	98,538
Investment securities held to maturity, gross unrealized gains	31	8
Investment securities held to maturity, gross unrealized losses	(2,430)	(2,238)
Investment securities held to maturity, at fair value	94,778	96,308
Investment securities held to maturity, at amortized cost	97,177	98,538
Investment securities held to maturity, gross unrealized losses	(2,430)	(2,238)
Other Debt Obligations [Member]
Investment securities held to maturity, at amortized cost	1,020	1,020
Investment securities held to maturity, gross unrealized gains
Investment securities held to maturity, gross unrealized losses
Investment securities held to maturity, at fair value	1,020	1,020
Investment securities held to maturity, at amortized cost	1,020	1,020
Investment securities held to maturity, gross unrealized losses

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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