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Note 2 - Securities - Fair Value of Securities Available for Sale and The Related Unrealized Gains and Losses Recognized in Accumulated Comprehensive Income (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Amortized Cost | $ 725,622 | $ 560,828
Gross Unrealized Gains | 8,825 | 14,856
Gross Unrealized Losses | (11,820) | (897)
Fair Value | 722,627 | 574,787
US Treasury and Government [Member] |  |
Amortized Cost | 2,005 | 2,007
Gross Unrealized Gains | 36 | 44
Gross Unrealized Losses | 0 | 0
Fair Value | 2,041 | 2,051
US Treasury Securities [Member] |  |
Amortized Cost | 11,954 | 1,996
Gross Unrealized Gains | 51 | 60
Gross Unrealized Losses | (141) | 0
Fair Value | 11,864 | 2,056
US States and Political Subdivisions Debt Securities [Member] |  |
Amortized Cost | 429,772 | 307,201
Gross Unrealized Gains | 7,209 | 13,191
Gross Unrealized Losses | (5,506) | (24)
Fair Value | 431,475 | 320,368
Collateralized Mortgage Backed Securities [Member] |  |
Amortized Cost | 276,592 | 246,085
Gross Unrealized Gains | 1,495 | 1,510
Gross Unrealized Losses | (6,164) | (872)
Fair Value | 271,923 | 246,723
Corporate Debt Securities [Member] |  |
Amortized Cost | 1,956 | 2,539
Gross Unrealized Gains | 34 | 51
Gross Unrealized Losses | 0 | (1)
Fair Value | 1,990 | 2,589
Trust Preferred Securities [Member] |  |
Amortized Cost | 1,000 | 1,000
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 1,000 | 1,000
Asset-backed Securities [Member] |  |
Amortized Cost | 2,343 |
Gross Unrealized Gains | 0 |
Gross Unrealized Losses | (9) |
Fair Value | $ 2,334 | $ 0

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- Definition 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). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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- Definition Amount, before tax, of unrealized loss 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). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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