LOANS AND ALLOWANCE FOR LOAN LOSSES - Non Traditional Mortgage Loans Additional Information (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 5,951,885	$ 7,700,873
FICOR score decrease (percent)	10.00%
Loan Portfolio \| Loan Portfolio Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage to total loans and leases (percent)	100.00%	100.00%
NTM Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 600,656	$ 826,731
NTM Loans \| Loan Portfolio \| Loan Portfolio Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage to total loans and leases (percent)	10.10%	10.70%
NTM Loans \| Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 600,656	$ 826,731
Increase (decrease) in loans receivable	$ (226,100)
Increase (decrease) in loans receivable (percent)	(27.30%)
NTM Loans \| Consumer \| First lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 598,357	824,318
NTM Loans \| Consumer \| Green Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 52,300	70,100
Interest only notes balloon payment period	15 years
NTM Loans \| Consumer \| Green Loans \| First lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 49,959	67,729
Increase (decrease) in loans receivable	(17,770)
NTM Loans \| Consumer \| Green Loans \| Nonperforming Financing Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,500	0
NTM Loans \| Consumer \| Interest only
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	545,400	753,100
NTM Loans \| Consumer \| Interest only \| First lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	545,371	753,061
NTM Loans \| Consumer \| Interest only \| Nonperforming Financing Receivables \| First lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,500	0
NTM Loans \| Consumer \| Negative amortization
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	3,000	3,500
NTM Loans \| Consumer \| Negative amortization \| First lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 3,027	$ 3,528
Number of non-performing loans \| loan	0	0

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