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Investment Securities Available-For-Sale (Details 2) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Schedule Of Available For Sale Debt Securities [Line Items] |  |  |
Total debt securities available-for-sale | $ 1,173,268 | $ 1,033,771 |
Gross Unrealized Gains | 24,660 | 8,424 |
Gross Unrealized Losses | (461) | (1,612) |
Investment securities available-for-sale | 1,197,467 | 1,040,583 |
Fair Value |  |  |
Less than 12 Months | 210,861 | 178,586 |
12 Months or Longer | 3,473 | 129,351 |
Total fair value | 214,334 | 307,937 |
Unrealized Losses |  |  |
Less than 12 Months | (451) | (661) |
12 Months or Longer | (10) | (951) |
Total unrealized losses | (461) | (1,612) |
Gross realized gains and losses |  |  |
Gross realized gains | 285 | 0 | $ 2
Gross realized losses | (6) | 0 | (347)
Net realized (losses) gains | 279 | 0 | $ (345)
Investment securities pledged as collateral | $ 338,680 | 281,380 |
Number of available-for-sale debt securities | 623 |  |
Number of available-for-sale debt securities in an unrealized loss position | 54 |  |
U.S. Treasury and Federal agencies securities |  |  |
Schedule Of Available For Sale Debt Securities [Line Items] |  |  |
Total debt securities available-for-sale | $ 610,195 | 524,896 |
Gross Unrealized Gains | 9,521 | 2,538 |
Gross Unrealized Losses | (234) | (470) |
Investment securities available-for-sale | 619,482 | 526,964 |
Fair Value |  |  |
Less than 12 Months | 136,534 | 87,352 |
12 Months or Longer | 0 | 69,053 |
Total fair value | 136,534 | 156,405 |
Unrealized Losses |  |  |
Less than 12 Months | (234) | (171) |
12 Months or Longer | 0 | (299) |
Total unrealized losses | (234) | (470) |
U.S. States and political subdivisions securities |  |  |
Schedule Of Available For Sale Debt Securities [Line Items] |  |  |
Total debt securities available-for-sale | 78,812 | 83,566 |
Gross Unrealized Gains | 2,346 | 1,048 |
Gross Unrealized Losses | (31) | (109) |
Investment securities available-for-sale | 81,127 | 84,505 |
Fair Value |  |  |
Less than 12 Months | 6,391 | 9,283 |
12 Months or Longer | 199 | 1,042 |
Total fair value | 6,590 | 10,325 |
Unrealized Losses |  |  |
Less than 12 Months | (30) | (107) |
12 Months or Longer | (1) | (2) |
Total unrealized losses | (31) | (109) |
Mortgage-backed securities - Federal agencies |  |  |
Schedule Of Available For Sale Debt Securities [Line Items] |  |  |
Total debt securities available-for-sale | 442,748 | 372,458 |
Gross Unrealized Gains | 11,237 | 3,948 |
Gross Unrealized Losses | (196) | (1,017) |
Investment securities available-for-sale | 453,789 | 375,389 |
Fair Value |  |  |
Less than 12 Months | 67,736 | 81,951 |
12 Months or Longer | 3,274 | 51,165 |
Total fair value | 71,010 | 133,116 |
Unrealized Losses |  |  |
Less than 12 Months | (187) | (383) |
12 Months or Longer | (9) | (634) |
Total unrealized losses | (196) | (1,017) |
Corporate debt securities |  |  |
Schedule Of Available For Sale Debt Securities [Line Items] |  |  |
Total debt securities available-for-sale | 40,813 | 52,151 |
Gross Unrealized Gains | 1,556 | 890 |
Gross Unrealized Losses | 0 | (16) |
Investment securities available-for-sale | 42,369 | 53,025 |
Fair Value |  |  |
Less than 12 Months | 0 | 0 |
12 Months or Longer | 0 | 8,091 |
Total fair value | 0 | 8,091 |
Unrealized Losses |  |  |
Less than 12 Months | 0 | 0 |
12 Months or Longer | 0 | (16) |
Total unrealized losses | 0 | (16) |
Foreign government and other securities |  |  |
Schedule Of Available For Sale Debt Securities [Line Items] |  |  |
Total debt securities available-for-sale | 700 | 700 |
Gross Unrealized Gains | 0 | 0 |
Gross Unrealized Losses | 0 | 0 |
Investment securities available-for-sale | 700 | 700 |
Fair Value |  |  |
Less than 12 Months | 200 | 0 |
12 Months or Longer | 0 | 0 |
Total fair value | 200 | 0 |
Unrealized Losses |  |  |
Less than 12 Months | 0 | 0 |
12 Months or Longer | 0 | 0 |
Total unrealized losses | $ 0 | $ 0 |

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