SECURITIES - Summary of Amortized Cost and Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	$ 1,255,195	$ 987,622
Available-for-sale Securities, Gross Unrealized Gains	29,603	35,045
Available-for-sale Securities, Gross Unrealized Losses	4,037	485
Available-for-sale securities, Fair Value	1,280,761	1,022,182
U.S Treasury
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	36,806	9,063
Available-for-sale Securities, Gross Unrealized Gains	205	320
Available-for-sale Securities, Gross Unrealized Losses	54	0
Available-for-sale securities, Fair Value	36,957	9,383
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	147,594	97,107
Available-for-sale Securities, Gross Unrealized Gains	2,965	3,130
Available-for-sale Securities, Gross Unrealized Losses	55	67
Available-for-sale securities, Fair Value	150,504	100,170
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	519,573	464,348
Available-for-sale Securities, Gross Unrealized Gains	13,757	16,326
Available-for-sale Securities, Gross Unrealized Losses	2,196	300
Available-for-sale securities, Fair Value	531,134	480,374
Mortgage-backed securities - residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	336,122	228,257
Available-for-sale Securities, Gross Unrealized Gains	6,243	8,206
Available-for-sale Securities, Gross Unrealized Losses	1,098	42
Available-for-sale securities, Fair Value	341,267	236,421
Mortgage-backed securities - commercial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	185,161	158,784
Available-for-sale Securities, Gross Unrealized Gains	4,948	6,087
Available-for-sale Securities, Gross Unrealized Losses	627	60
Available-for-sale securities, Fair Value	189,482	164,811
Corporate obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available-for-sale Securities, Amortized Cost	29,939	30,063
Available-for-sale Securities, Gross Unrealized Gains	1,485	976
Available-for-sale Securities, Gross Unrealized Losses	7	16
Available-for-sale securities, Fair Value	$ 31,417	$ 31,023

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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