LOANS AND ALLOWANCE FOR CREDIT LOSSES - Non Traditional Mortgage Performance by Credit Score (Details) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 5,898,405	$ 5,951,885
NTM Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 437,113	$ 600,656
Consumer \| NTM Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	344	461
Total loans	$ 437,113	$ 600,656
Increase (decrease) in loans receivable	$ (163,500)
Increase (decrease) in loans receivable (percent)	(27.20%)
Consumer \| NTM Loans \| First lien
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	339	454
Total loans	$ 435,515	$ 598,357
Consumer \| NTM Loans \| Green Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	$ 33,200	$ 52,300
Consumer \| NTM Loans \| Green Loans \| First lien
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	48	69
Total loans	$ 31,587	$ 49,959
Consumer \| NTM Loans \| Green Loans \| First lien \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	48	48
Total loans	$ 31,587	$ 31,587
Percentage to total loans and leases (percent)	100.00%	100.00%
Increase (decrease) in count of loans receivable \| loan	0
Increase (decrease) in loans receivable	$ 0
Increase (decrease) in loans receivable (percent)	0.00%
Consumer \| NTM Loans \| Green Loans \| First lien \| Greater than 800 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	11	12
Total loans	$ 5,773	$ 3,130
Percentage to total loans and leases (percent)	18.30%	9.90%
Increase (decrease) in count of loans receivable \| loan	(1)
Increase (decrease) in loans receivable	$ 2,643
Increase (decrease) in loans receivable (percent)	84.40%
Consumer \| NTM Loans \| Green Loans \| First lien \| 700-799 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	24	24
Total loans	$ 16,472	$ 17,408
Percentage to total loans and leases (percent)	52.10%	55.10%
Increase (decrease) in count of loans receivable \| loan	0
Increase (decrease) in loans receivable	$ (936)
Increase (decrease) in loans receivable (percent)	(5.40%)
Consumer \| NTM Loans \| Green Loans \| First lien \| 600-699 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	9	6
Total loans	$ 7,717	$ 7,959
Percentage to total loans and leases (percent)	24.40%	25.20%
Increase (decrease) in count of loans receivable \| loan	3
Increase (decrease) in loans receivable	$ (242)
Increase (decrease) in loans receivable (percent)	(3.00%)
Consumer \| NTM Loans \| Green Loans \| First lien \| Less than 600 \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	2	4
Total loans	$ 1,097	$ 2,562
Percentage to total loans and leases (percent)	3.50%	8.10%
Increase (decrease) in count of loans receivable \| loan	(2)
Increase (decrease) in loans receivable	$ (1,465)
Increase (decrease) in loans receivable (percent)	(57.20%)
Consumer \| NTM Loans \| Green Loans \| First lien \| No FICO score \| Loan Portfolio Concentration Risk \| Non-Traditional Single Family Residential Mortgage Green Loans First Lien Portfolio
Financing Receivable, Credit Quality Indicator [Line Items]
Count \| loan	2	2
Total loans	$ 528	$ 528
Percentage to total loans and leases (percent)	1.70%	1.70%
Increase (decrease) in count of loans receivable \| loan	0
Increase (decrease) in loans receivable	$ 0
Increase (decrease) in loans receivable (percent)	0.00%

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Loans and Leases Receivable, Increase (Decrease) in Number of Loans

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount, before allowance for credit loss, of financing receivable.

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