SECURITIES - Summary of Amortized Cost and Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	$ 987,622	$ 751,591
Available-for-sale Securities, Gross Unrealized Gains	35,045	14,419
Available-for-sale Securities, Gross Unrealized Losses	485	923
Available-for-sale securities, Fair Value	1,022,182	765,087
U.S Treasury
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	9,063	4,967
Available-for-sale Securities, Gross Unrealized Gains	320	0
Available-for-sale Securities, Gross Unrealized Losses	0	73
Available-for-sale securities, Fair Value	9,383	4,894
Obligations of U.S. government agencies and sponsored entities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	97,107	76,699
Available-for-sale Securities, Gross Unrealized Gains	3,130	1,475
Available-for-sale Securities, Gross Unrealized Losses	67	224
Available-for-sale securities, Fair Value	100,170	77,950
Tax-exempt and taxable obligations of states and municipal subdivisions
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	464,348	253,527
Available-for-sale Securities, Gross Unrealized Gains	16,326	5,602
Available-for-sale Securities, Gross Unrealized Losses	300	147
Available-for-sale securities, Fair Value	480,374	258,982
Mortgage-backed securities - residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	228,257	263,229
Available-for-sale Securities, Gross Unrealized Gains	8,206	4,726
Available-for-sale Securities, Gross Unrealized Losses	42	107
Available-for-sale securities, Fair Value	236,421	267,848
Mortgage-backed securities - commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	158,784	125,292
Available-for-sale Securities, Gross Unrealized Gains	6,087	2,398
Available-for-sale Securities, Gross Unrealized Losses	60	223
Available-for-sale securities, Fair Value	164,811	127,467
Corporate obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	30,063	27,877
Available-for-sale Securities, Gross Unrealized Gains	976	218
Available-for-sale Securities, Gross Unrealized Losses	16	149
Available-for-sale securities, Fair Value	$ 31,023	$ 27,946

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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Amount of unrealized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

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Amount of unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

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