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SECURITIES - Securities Available for Sale (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020
Amortized cost and estimated fair value of securities available for sale [Abstract] |  |  |
Amortized Cost | $ 627,578,000 |  | $ 542,362,000
Unrealized Gains | 8,055,000 |  | 12,654,000
Unrealized Losses | 9,438,000 |  | 405,000
Estimated Fair Value | 626,195,000 |  | 554,611,000
Amortized Cost [Abstract] |  |  |
Within one year | 610,000 |  |
After one, but within five years | 31,385,000 |  |
After five, but within ten years | 17,487,000 |  |
After ten years | 758,000 |  |
Total | 50,240,000 |  |
Amortized Cost | 627,578,000 |  | 542,362,000
Fair Value [Abstract] |  |  |
Within one year | 611,000 |  |
After one, but within five years | 32,858,000 |  |
After five, but within ten years | 18,234,000 |  |
After ten years | 806,000 |  |
Total | 52,509,000 |  |
Fair value | 626,195,000 |  | 554,611,000
Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] |  |  |
Proceeds form sale of securities resulting in gain (loss) | 0 | $ 0 |
Obligations of U.S. Government and U.S. Government sponsored enterprises |  |  |
Amortized cost and estimated fair value of securities available for sale [Abstract] |  |  |
Amortized Cost | 610,000 |  |
Unrealized Gains | 1,000 |  |
Unrealized Losses | 0 |  |
Estimated Fair Value | 611,000 |  |
Amortized Cost [Abstract] |  |  |
Amortized Cost | 610,000 |  |
Fair Value [Abstract] |  |  |
Fair value | 611,000 |  |
Mortgage-backed securities, residential |  |  |
Amortized cost and estimated fair value of securities available for sale [Abstract] |  |  |
Amortized Cost | 523,974,000 |  | 458,245,000
Unrealized Gains | 5,698,000 |  | 9,822,000
Unrealized Losses | 9,175,000 |  | 201,000
Estimated Fair Value | 520,497,000 |  | 467,866,000
Amortized Cost [Abstract] |  |  |
Without single maturity date | 523,974,000 |  |
Amortized Cost | 523,974,000 |  | 458,245,000
Fair Value [Abstract] |  |  |
Without single maturity date | 520,497,000 |  |
Fair value | 520,497,000 |  | 467,866,000
Obligations of states and political subdivisions |  |  |
Amortized cost and estimated fair value of securities available for sale [Abstract] |  |  |
Amortized Cost | 40,630,000 |  | 40,662,000
Unrealized Gains | 2,192,000 |  | 2,743,000
Unrealized Losses | 0 |  | 0
Estimated Fair Value | 42,822,000 |  | 43,405,000
Amortized Cost [Abstract] |  |  |
Amortized Cost | 40,630,000 |  | 40,662,000
Fair Value [Abstract] |  |  |
Fair value | 42,822,000 |  | 43,405,000
Corporate bonds and notes |  |  |
Amortized cost and estimated fair value of securities available for sale [Abstract] |  |  |
Amortized Cost | 9,000,000 |  | 9,000,000
Unrealized Gains | 112,000 |  | 47,000
Unrealized Losses | 36,000 |  | 12,000
Estimated Fair Value | 9,076,000 |  | 9,035,000
Amortized Cost [Abstract] |  |  |
Amortized Cost | 9,000,000 |  | 9,000,000
Fair Value [Abstract] |  |  |
Fair value | 9,076,000 |  | 9,035,000
SBA loan pools |  |  |
Amortized cost and estimated fair value of securities available for sale [Abstract] |  |  |
Amortized Cost | 53,364,000 |  | 34,455,000
Unrealized Gains | 52,000 |  | 42,000
Unrealized Losses | 227,000 |  | 192,000
Estimated Fair Value | 53,189,000 |  | 34,305,000
Amortized Cost [Abstract] |  |  |
Without single maturity date | 53,364,000 |  |
Amortized Cost | 53,364,000 |  | 34,455,000
Fair Value [Abstract] |  |  |
Without single maturity date | 53,189,000 |  |
Fair value | $ 53,189,000 |  | $ 34,305,000

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