LOAN SERVICING RIGHTS - Schedule of Sensitivity of Fair Value to Adverse Changes in Model Inputs and/or Assumptions (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Residential mortgage
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Unpaid principal balance of loans serviced for others	$ 14,171,621	$ 13,764,529
Loans serviced for others, percentage	100.00%	100.00%
Weighted average life (in years)	340 months	340 months
Weighted average age	20 months	20 months
Modeled prepayment speed	13.37%	18.82%
Decline in fair value due to a 10% adverse change	$ (6,886)	$ (7,154)
Decline in fair value due to a 20% adverse change	$ (13,262)	$ (13,664)
Weighted average discount rate	8.76%	9.50%
Decline in fair value due to a 10% adverse change	$ (5,522)	$ (4,304)
Decline in fair value due to a 20% adverse change	$ (10,671)	$ (8,321)
Residential mortgage \| FHLMC
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Loans serviced for others, percentage	21.05%	21.55%
Residential mortgage \| FNMA
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Loans serviced for others, percentage	61.40%	61.75%
Residential mortgage \| GNMA
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Loans serviced for others, percentage	17.55%	16.70%
SBA servicing rights
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Unpaid principal balance of loans serviced for others	$ 437,989	$ 351,325
Weighted average life (in years)	3 years 5 months 26 days	3 years 5 months 15 days
Modeled prepayment speed	19.05%	19.14%
Decline in fair value due to a 10% adverse change	$ (412)	$ (335)
Decline in fair value due to a 20% adverse change	$ (783)	$ (636)
Weighted average discount rate	7.09%	9.55%
Decline in fair value due to a 10% adverse change	$ (188)	$ (151)
Decline in fair value due to a 20% adverse change	$ (367)	$ (295)

Loans Serviced For Others, Percentage

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- Definition

Servicing Assets And Servicing Liabilities At Fair Value, Assumptions Used To Estimate Fair Value, Weighted Average Age

+ References

No definition available.

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- Definition

This is the sum of principal amount outstanding for both securitized and unsecuritized loans of all types.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

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- Definition

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

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- Definition

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

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The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

A specified percentage variance in the discount rate assumption in the determination of fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

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A specified percentage variance in the prepayment speed assumption in the determination of fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities).

+ References

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- Definition

Weighted average life of financial assets and financial liabilities, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122596-111746

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