Note 5 - Investment Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available for sale securities in a continuous unrealized loss position, less than 12 months, fair value	$ 54,959	$ 97,264
Available for sale securities in a continuous unrealized loss position, less than 12 months, unrealized losses	155	960
Available for sale securities in a continuous unrealized loss position, 12 months or more, fair value	95,553	64,457
Available for sale securities in a continuous unrealized loss position, 12 months or more, unrealized losses	3,884	3,297
Available for sale securities in a continuous unrealized loss position, fair value	150,512	161,721
Available for sale securities in a continuous unrealized loss position, unrealized losses	4,039	4,257
Held to maturity securities in a continuous unrealized loss position, less than 12 months, fair value	18,567	71,347
Held to maturity securities in a continuous unrealized loss position, less than 12 months, unrealized losses	78	271
Held to maturity securities in a continuous unrealized loss position, 12 months or more, fair value	494	120,159
Held to maturity securities in a continuous unrealized loss position, 12 months or more, unrealized losses	3	1,329
Held to maturity securities in a continuous unrealized loss position, fair value	19,061	191,506
Held to maturity securities in a continuous unrealized loss position, unrealized losses	81	1,600
US Government Agencies Debt Securities [Member]
Available for sale securities in a continuous unrealized loss position, less than 12 months, fair value	8,254	28,136
Available for sale securities in a continuous unrealized loss position, less than 12 months, unrealized losses	89	439
Available for sale securities in a continuous unrealized loss position, 12 months or more, fair value	25,118	0
Available for sale securities in a continuous unrealized loss position, 12 months or more, unrealized losses	387	0
Available for sale securities in a continuous unrealized loss position, fair value	33,372	28,136
Available for sale securities in a continuous unrealized loss position, unrealized losses	476	439
Held to maturity securities in a continuous unrealized loss position, less than 12 months, fair value	0	33,092
Held to maturity securities in a continuous unrealized loss position, less than 12 months, unrealized losses	0	220
Held to maturity securities in a continuous unrealized loss position, 12 months or more, fair value	0	3,703
Held to maturity securities in a continuous unrealized loss position, 12 months or more, unrealized losses	0	74
Held to maturity securities in a continuous unrealized loss position, fair value	0	36,795
Held to maturity securities in a continuous unrealized loss position, unrealized losses	0	294
Collateralized Mortgage Obligations [Member]
Available for sale securities in a continuous unrealized loss position, less than 12 months, fair value	44,918	63,384
Available for sale securities in a continuous unrealized loss position, less than 12 months, unrealized losses	60	328
Available for sale securities in a continuous unrealized loss position, 12 months or more, fair value	15,929	6,164
Available for sale securities in a continuous unrealized loss position, 12 months or more, unrealized losses	3	94
Available for sale securities in a continuous unrealized loss position, fair value	60,847	69,548
Available for sale securities in a continuous unrealized loss position, unrealized losses	63	422
Held to maturity securities in a continuous unrealized loss position, less than 12 months, fair value	13,625	24,211
Held to maturity securities in a continuous unrealized loss position, less than 12 months, unrealized losses	51	18
Held to maturity securities in a continuous unrealized loss position, 12 months or more, fair value	494	64,324
Held to maturity securities in a continuous unrealized loss position, 12 months or more, unrealized losses	3	775
Held to maturity securities in a continuous unrealized loss position, fair value	14,119	88,535
Held to maturity securities in a continuous unrealized loss position, unrealized losses	54	793
Agency Mortgage-backed Securities [Member]
Available for sale securities in a continuous unrealized loss position, less than 12 months, fair value	1,787	2,924
Available for sale securities in a continuous unrealized loss position, less than 12 months, unrealized losses	6	13
Available for sale securities in a continuous unrealized loss position, 12 months or more, fair value	0	6,411
Available for sale securities in a continuous unrealized loss position, 12 months or more, unrealized losses	0	85
Available for sale securities in a continuous unrealized loss position, fair value	1,787	9,335
Available for sale securities in a continuous unrealized loss position, unrealized losses	6	98
Held to maturity securities in a continuous unrealized loss position, less than 12 months, fair value	4,942	14,044
Held to maturity securities in a continuous unrealized loss position, less than 12 months, unrealized losses	27	33
Held to maturity securities in a continuous unrealized loss position, 12 months or more, fair value	0	52,132
Held to maturity securities in a continuous unrealized loss position, 12 months or more, unrealized losses	0	480
Held to maturity securities in a continuous unrealized loss position, fair value	4,942	66,176
Held to maturity securities in a continuous unrealized loss position, unrealized losses	27	513
US States and Political Subdivisions Debt Securities [Member]
Available for sale securities in a continuous unrealized loss position, less than 12 months, fair value	0	0
Available for sale securities in a continuous unrealized loss position, less than 12 months, unrealized losses	0	0
Available for sale securities in a continuous unrealized loss position, 12 months or more, fair value	0	0
Available for sale securities in a continuous unrealized loss position, 12 months or more, unrealized losses	0	0
Available for sale securities in a continuous unrealized loss position, fair value	0	0
Available for sale securities in a continuous unrealized loss position, unrealized losses	0	0
Corporate Debt Securities [Member]
Available for sale securities in a continuous unrealized loss position, less than 12 months, fair value	0	2,820
Available for sale securities in a continuous unrealized loss position, less than 12 months, unrealized losses	0	180
Available for sale securities in a continuous unrealized loss position, 12 months or more, fair value	54,506	51,882
Available for sale securities in a continuous unrealized loss position, 12 months or more, unrealized losses	3,494	3,118
Available for sale securities in a continuous unrealized loss position, fair value	54,506	54,702
Available for sale securities in a continuous unrealized loss position, unrealized losses	$ 3,494	$ 3,298

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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