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INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) | Dec. 31, 2019 USD ($) Position | Dec. 31, 2018 USD ($) Position
--- | --- | ---
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 88 | 169
12 months or longer | Position | 62 | 384
Total | Position | 150 | 553
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 710,602,000 | $ 576,527,000
12 months or longer | 83,378,000 | 1,584,618,000
Total | 793,980,000 | 2,161,145,000
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 8,351,000 | 1,156,000
12 months or longer | 789,000 | 25,412,000
Total | $ 9,140,000 | $ 26,568,000
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 |  | $ 82,000
12 months or longer |  | 0
Total |  | 82,000
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months |  | 19,000
12 months or longer |  | 0
Total |  | $ 19,000
U.S. Treasury and Agency Securities [Member] |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 12 | 7
12 months or longer | Position | 5 | 64
Total | Position | 17 | 71
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 592,678,000 | $ 473,082,000
12 months or longer | 25,998,000 | 1,213,276,000
Total | 618,676,000 | 1,686,358,000
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 7,970,000 | 682,000
12 months or longer | 5,000 | 14,229,000
Total | $ 7,975,000 | $ 14,911,000
Obligations of State and Political Subdivisions [Member] |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 21 | 118
12 months or longer | Position | 0 | 97
Total | Position | 21 | 215
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 22,716,000 | $ 55,671,000
12 months or longer | 0 | 51,753,000
Total | 22,716,000 | 107,424,000
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 26,000 | 216,000
12 months or longer | 0 | 833,000
Total | $ 26,000 | $ 1,049,000
Government Agency Mortgage-Backed Securities [Member] |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 50 | 43
12 months or longer | Position | 52 | 181
Total | Position | 102 | 224
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 89,237,000 | $ 47,708,000
12 months or longer | 52,975,000 | 253,931,000
Total | 142,212,000 | 301,639,000
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 341,000 | 258,000
12 months or longer | 766,000 | 9,025,000
Total | $ 1,107,000 | $ 9,283,000
Corporate Debt Securities [Member] |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position |  | 0
12 months or longer | Position |  | 1
Total | Position |  | 1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months |  | $ 0
12 months or longer |  | 2,546,000
Total |  | 2,546,000
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months |  | 0
12 months or longer |  | 42,000
Total |  | $ 42,000
Government Agency Collateralized Mortgage Obligations [Member] |  |
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract] |  |
Less than 12 months | Position | 5 | 1
12 months or longer | Position | 5 | 41
Total | Position | 10 | 42
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 months | $ 5,971,000 | $ 66,000
12 months or longer | 4,405,000 | 63,112,000
Total | 10,376,000 | 63,178,000
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months | 14,000 | 0
12 months or longer | 18,000 | 1,283,000
Total | $ 32,000 | $ 1,283,000
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 |  | $ 82,000
12 months or longer |  | 0
Total |  | 82,000
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses [Abstract] |  |
Less than 12 months |  | 19,000
12 months or longer |  | 0
Total |  | $ 19,000

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