LOANS AND ALLOWANCE FOR CREDIT LOSSES - Non Traditional Mortgages Portfolio (Detail) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 5,678,002	$ 5,951,885
NTM Loans | Loan Portfolio Concentration Risk | Loan Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	8.30%	10.10%
Consumer | NTM Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	365	461
Total loans	$ 468,496	$ 600,656
Consumer | NTM Loans | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	100.00%	100.00%
Consumer | NTM Loans | Green Loans (HELOC) - first liens
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	360	454
Total loans	$ 466,888	$ 598,357
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	99.70%	99.60%
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Green Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	57	69
Total loans	$ 39,180	$ 49,959
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Green Loans | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	8.40%	8.30%
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Interest Only Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	295	376
Total loans	$ 425,406	$ 545,371
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Interest Only Loans | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	90.80%	90.80%
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Negative amortization
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	8	9
Total loans	$ 2,302	$ 3,027
Consumer | NTM Loans | Green Loans (HELOC) - first liens | Negative amortization | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	0.50%	0.50%
Consumer | NTM Loans | Green Loans (HELOC) - second liens
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	5	7
Total loans	$ 1,608	$ 2,299
Consumer | NTM Loans | Green Loans (HELOC) - second liens | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	0.30%	0.40%
Consumer | NTM Loans | Green Loans (HELOC) - second liens | Green Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Count | loan	5	7
Total loans	$ 1,608	$ 2,299
Consumer | NTM Loans | Green Loans (HELOC) - second liens | Green Loans | Loan Portfolio Concentration Risk | Nontraditional Mortgage Loans Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk percentage (percent)	0.30%	0.40%