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INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) | Jun. 30, 2020 USD ($) Position | Dec. 31, 2019 USD ($) Position
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Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 219 | 88
12 months or longer | Position | 3 | 62
Total | Position | 222 | 150
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 124,839,000 | $ 710,602,000
12 months or longer | 15,000 | 83,378,000
Total | 124,854,000 | 793,980,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 292,000 | 8,351,000
12 months or longer | 0 | 789,000
Total | $ 292,000 | $ 9,140,000
Equity and Other Securities, Continuous Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 1 |
12 months or longer | Position | 0 |
Total | Position | 1 |
Equity and Other Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 79,000 |
12 months or longer | 0 |
Total | 79,000 |
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 22,000 |
12 months or longer | 0 |
Total | 22,000 |
Available-for-sale, allowance for credit losses | $ 0 |
U.S. Treasury and Agency Securities [Member] |  |
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 8 | 12
12 months or longer | Position | 0 | 5
Total | Position | 8 | 17
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 12,058,000 | $ 592,678,000
12 months or longer | 0 | 25,998,000
Total | 12,058,000 | 618,676,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 18,000 | 7,970,000
12 months or longer | 0 | 5,000
Total | $ 18,000 | $ 7,975,000
Obligations of State and Political Subdivisions [Member] |  |
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 52 | 21
12 months or longer | Position | 0 | 0
Total | Position | 52 | 21
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 20,145,000 | $ 22,716,000
12 months or longer | 0 | 0
Total | 20,145,000 | 22,716,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 20,000 | 26,000
12 months or longer | 0 | 0
Total | $ 20,000 | $ 26,000
Government Agency Mortgage-Backed Securities [Member] |  |
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 142 | 50
12 months or longer | Position | 2 | 52
Total | Position | 144 | 102
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 87,290,000 | $ 89,237,000
12 months or longer | 15,000 | 52,975,000
Total | 87,305,000 | 142,212,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 248,000 | 341,000
12 months or longer | 0 | 766,000
Total | $ 248,000 | $ 1,107,000
Government Agency Collateralized Mortgage Obligations [Member] |  |
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 17 | 5
12 months or longer | Position | 1 | 5
Total | Position | 18 | 10
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 5,346,000 | $ 5,971,000
12 months or longer | 0 | 4,405,000
Total | 5,346,000 | 10,376,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 6,000 | 14,000
12 months or longer | 0 | 18,000
Total | $ 6,000 | $ 32,000
Equity Securities, at Fair Value [Member] |  |
Equity and Other Securities, Continuous Unrealized Loss Position, Number of Positions [Abstract] |  |
Less than 12 months | Position | 1 |
12 months or longer | Position | 0 |
Total | Position | 1 |
Equity and Other Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 79,000 |
12 months or longer | 0 |
Total | 79,000 |
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 22,000 |
12 months or longer | 0 |
Total | $ 22,000 |

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