Note 3 - Securities - Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Securities available-for-sale, less than 12 months, fair value	$ 183,279	$ 100,662
Securities available-for-sale, less than 12 months, unrealized losses	(151)	(44)
Securities available-for-sale, 12 months or more, fair value	258,555	287,807
Securities available-for-sale, 12 months or more, unrealized losses	(3,977)	(7,248)
Securities available-for-sale, fair value	441,834	388,469
Securities available-for-sale, unrealized losses	(4,128)	(7,292)
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value	183,279	96,740
Securities available-for-sale, less than 12 months, unrealized losses	(151)	(38)
Securities available-for-sale, 12 months or more, fair value	133,375	149,320
Securities available-for-sale, 12 months or more, unrealized losses	(1,712)	(3,313)
Securities available-for-sale, fair value	316,654	246,060
Securities available-for-sale, unrealized losses	(1,863)	(3,351)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale, less than 12 months, fair value		3,108
Securities available-for-sale, less than 12 months, unrealized losses		(5)
Securities available-for-sale, 12 months or more, fair value	109,690	120,848
Securities available-for-sale, 12 months or more, unrealized losses	(2,207)	(3,748)
Securities available-for-sale, fair value	109,690	123,956
Securities available-for-sale, unrealized losses	(2,207)	(3,753)
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value		814
Securities available-for-sale, less than 12 months, unrealized losses		(1)
Securities available-for-sale, 12 months or more, fair value	15,490	17,639
Securities available-for-sale, 12 months or more, unrealized losses	(58)	(187)
Securities available-for-sale, fair value	15,490	18,453
Securities available-for-sale, unrealized losses	$ (58)	$ (188)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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