LOANS AND LEASES AND ALLOWANCE FOR LOAN AND LEASE LOSSES - Non Traditional Mortgage Loans Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 6,568,791,000	$ 5,184,394,000	$ 4,730,077,000
Percentage decrease in credit score to run exception report	10.00%
Non-Traditional Mortgages (NTM)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 891,083,000	785,908,000
Consumer | Non-Traditional Mortgages (NTM)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	891,083,000	785,908,000
Increase (decrease) in loans receivable	$ 105,200,000
Increase (decrease) in loans receivable, percentage	13.40%
Consumer | Non-Traditional Mortgages (NTM) | Green Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 101,200,000	109,800,000
Interest only notes balloon payment period	15 years
Consumer | Non-Traditional Mortgages (NTM) | Green Loans | Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 8,700,000	10,100,000
Consumer | Non-Traditional Mortgages (NTM) | Interest Only Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	780,100,000	664,500,000
Consumer | Non-Traditional Mortgages (NTM) | Interest Only Loans | Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,700,000	4,600,000
Consumer | Non-Traditional Mortgages (NTM) | Negative amortization
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,900,000	11,600,000
Consumer | Non-Traditional Mortgages (NTM) | Negative amortization | Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 0	$ 0
Consumer | Non-Traditional Mortgages (NTM) | Loan Portfolio | Loan Portfolio Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage	13.60%	15.20%