DEPOSITS - Narrative (Details) - USD ($) $ in Millions	Apr. 01, 2020	Sep. 30, 2020
Deposits [Abstract]
Deposits liabilities upon acquisition	$ 2,300.0
Certificates of deposit	752.4
Fair value premium adjustment	$ 14.7	$ 9.8
Deposit premium amortization period	5 years

Amount, after accumulated amortization, of debt discount (premium).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Section 55
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