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LOANS AND ALLOWANCE FOR LOAN LOSSES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Total loans acquired as overdrafts	$ 1,659,535,000	$ 1,359,544,000	$ 1,243,925,000
Loans to related parties	56,199,000	44,506,000
Unfunded commitments of related party loans	16,383,000
Interest income if accrual method	333,000	173,000
Increase in allowance for loan losses due to TDRs	0	0
Troubled debt restructuring charge-offs	0	$ 0
Westbound Bank
Financing Receivable, Impaired [Line Items]
Total loans acquired as overdrafts	$ 2,000

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Financing Receivables, Impaired, Troubled Debt Restructuring, Increase in Allowance for Loan Losses

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Loan and Lease Receivable, Unfunded Commitment, Related Parties

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reflects the amount of the write-down related to a troubled debt restructuring.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

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For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date.

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