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LOANS - Narrative (Details)	12 Months Ended
LOANS - Narrative (Details)	Dec. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($) contract	Dec. 31, 2017 USD ($) contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reclassifications of loans to loans held for sale	$ 120,307,000	$ 0	$ 0
Payments to acquire loans and leases held-for-investment	432,000,000	567,000,000
Proceeds from sale of loans and leases held-for-investment	310,000,000	388,000,000
Gain (loss) on sales of loans, net	12,000,000.0	9,300,000	$ 11,700,000
Total loans	9,502,428,000	9,043,253,000
Loans pledged as collateral	285,000,000
Due to related parties	1,800,000	52,900,000
Loans receivable, related parties	1,000,000.0	$ 47,800,000
Additional funds committed amount	$ 0
Borrower's sustained repayment performance period	6 months
Number of contracts \| contract	1	0	3
Aircraft Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reclassifications of loans to loans held for sale	$ 50,000,000
Homeowners Association Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reclassifications of loans to loans held for sale	29,000,000
SBA Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reclassifications of loans to loans held for sale	29,000,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,034,269,000	$ 3,400,221,000
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,840,508,000	1,980,046,000
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,685,472,000	2,566,424,000
Residential \| Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Process of foreclosure	0	0
Residential \| Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Process of foreclosure	6,500,000	3,200,000
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	942,179,000	1,096,562,000
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,335,931,000	1,676,509,000
Gross contractual receivable amounts at acquisition	61,400,000	47,300,000
Acquired credit impaired loans, note balance	147,000,000	124,000,000
Acquired Loans \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,237,313,000	811,510,000
Gross contractual receivable amounts at acquisition	23,100,000	12,000,000.0
Acquired Loans \| Commercial real estate \| Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,189,521,000	786,290,000
Acquired Loans \| Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	397,891,000	466,508,000
Gross contractual receivable amounts at acquisition	26,700,000	29,500,000
Acquired Loans \| Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	537,014,000	239,126,000
Gross contractual receivable amounts at acquisition	10,800,000	4,900,000
Acquired Loans \| Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	163,713,000	159,365,000
Gross contractual receivable amounts at acquisition	800,000	900,000
Total Loans \| 6512 Operators of Nonresidential Buildings \| Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 1,700,000,000	$ 1,400,000,000
Concentration risk, percentage	18.10%	15.60%