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Note 6 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Equity securities at fair value (Note 2) | $ 3,804 | $ 2,896
Securities available for sale (Note 2) | 722,627 | 574,787
Equity Securities [Member] |  |
Equity securities at fair value (Note 2) |  | 2,896
US Treasury and Government [Member] |  |
Securities available for sale (Note 2) | 2,041 | 2,051
US Treasury Securities [Member] |  |
Securities available for sale (Note 2) | 11,864 | 2,056
US States and Political Subdivisions Debt Securities [Member] |  |
Securities available for sale (Note 2) | 431,475 | 320,368
Collateralized Mortgage Backed Securities [Member] |  |
Equity securities at fair value (Note 2) | 3,804 |
Securities available for sale (Note 2) | 271,923 | 246,723
Corporate Debt Securities [Member] |  |
Securities available for sale (Note 2) | 1,990 | 2,589
Trust Preferred Securities [Member] |  |
Securities available for sale (Note 2) | 1,000 | 1,000
Asset-backed Securities [Member] |  |
Securities available for sale (Note 2) | 2,334 | 0
Fair Value, Recurring [Member] |  |
Securities available for sale (Note 2) |  | 574,787
Fair Value, Recurring [Member] | Equity Securities [Member] |  |
Equity securities at fair value (Note 2) | 3,804 | 2,896
Fair Value, Recurring [Member] | US Treasury and Government [Member] |  |
Securities available for sale (Note 2) | 2,041 | 2,051
Fair Value, Recurring [Member] | US Treasury Securities [Member] |  |
Securities available for sale (Note 2) | 11,864 | 2,056
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Securities available for sale (Note 2) | 431,475 | 320,368
Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Securities available for sale (Note 2) | 271,923 | 246,723
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |
Securities available for sale (Note 2) | 1,990 | 2,589
Fair Value, Recurring [Member] | Trust Preferred Securities [Member] |  |
Securities available for sale (Note 2) | 1,000 | 1,000
Fair Value, Recurring [Member] | Asset-backed Securities [Member] |  |
Securities available for sale (Note 2) | 2,334 |
Fair Value, Inputs, Level 1 [Member] |  |
Securities available for sale (Note 2) | 0 |
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] |  |
Securities available for sale (Note 2) |  | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member] |  |
Equity securities at fair value (Note 2) | 1,859 | 1,411
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Trust Preferred Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Asset-backed Securities [Member] |  |
Securities available for sale (Note 2) | 0 |
Fair Value, Inputs, Level 2 [Member] |  |
Securities available for sale (Note 2) | 709,021 |
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] |  |
Securities available for sale (Note 2) |  | 563,364
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member] |  |
Equity securities at fair value (Note 2) | 0 | 0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member] |  |
Securities available for sale (Note 2) | 2,041 | 2,051
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member] |  |
Securities available for sale (Note 2) | 11,864 | 2,056
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Securities available for sale (Note 2) | 418,869 | 309,945
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Securities available for sale (Note 2) | 271,923 | 246,723
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |
Securities available for sale (Note 2) | 1,990 | 2,589
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Trust Preferred Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Asset-backed Securities [Member] |  |
Securities available for sale (Note 2) | 2,334 |
Fair Value, Inputs, Level 3 [Member] |  |
Securities available for sale (Note 2) | 13,606 |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] |  |
Securities available for sale (Note 2) |  | 11,423
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member] |  |
Equity securities at fair value (Note 2) | 1,945 | 1,485
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US Treasury Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Securities available for sale (Note 2) | 12,606 | 10,423
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |
Securities available for sale (Note 2) | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Trust Preferred Securities [Member] |  |
Securities available for sale (Note 2) | 1,000 | $ 1,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Asset-backed Securities [Member] |  |
Securities available for sale (Note 2) | $ 0 |

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