FAIR VALUE MEASURES - Significant Unobservable Inputs Used in Fair Value Measurement of Level 3 Assets and Liabilities (Details) $ in Thousands	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, at fair value	$ 859,652	$ 982,879
Other real estate owned, at fair value	8,841	11,880
Fair Value, Measurements, Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, at fair value	1,170	1,170
Fair Value, Measurements, Nonrecurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral-dependent loans, at fair value	93,058	98,426
Other real estate owned, at fair value	299	4,964
Mortgage Servicing Rights	$ 154,746	$ 130,630
Discounted par values \| Probability of default \| Fair Value, Measurements, Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.171	0.188
Discounted par values \| Probability of default \| Fair Value, Measurements, Recurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.171	0.188
Discounted par values \| Loss given default \| Fair Value, Measurements, Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.39
Discounted par values \| Loss given default \| Fair Value, Measurements, Recurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.39
Discounted par values \| Loss given default \| Fair Value, Measurements, Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input		0.40
Discounted par values \| Loss given default \| Fair Value, Measurements, Recurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input		0.40
Third-party appraisals and discounted cash flows \| Collateral discounts and discount rates \| Fair Value, Measurements, Nonrecurring \| Minimum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral-dependent loans, measurement input	20.00%	20.00%
Third-party appraisals and discounted cash flows \| Collateral discounts and discount rates \| Fair Value, Measurements, Nonrecurring \| Maximum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral-dependent loans, measurement input	57.00%	90.00%
Third-party appraisals and discounted cash flows \| Collateral discounts and discount rates \| Fair Value, Measurements, Nonrecurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral-dependent loans, measurement input	44.00%	44.00%
Third-party appraisals and sales contracts \| Collateral discounts and estimated costs to sell \| Fair Value, Measurements, Nonrecurring \| Minimum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned, measurement input	0.15	0.15
Third-party appraisals and sales contracts \| Collateral discounts and estimated costs to sell \| Fair Value, Measurements, Nonrecurring \| Maximum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned, measurement input	0.36	0.59
Third-party appraisals and sales contracts \| Collateral discounts and estimated costs to sell \| Fair Value, Measurements, Nonrecurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned, measurement input	0.27	0.28
Discounted cash flows \| Discount rate \| Fair Value, Measurements, Nonrecurring \| Minimum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights Measurement Input	0.09	0.09
Discounted cash flows \| Discount rate \| Fair Value, Measurements, Nonrecurring \| Maximum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights Measurement Input	0.10	0.12
Discounted cash flows \| Discount rate \| Fair Value, Measurements, Nonrecurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights Measurement Input	0.09	0.10
Discounted cash flows \| Prepayment speed \| Fair Value, Measurements, Nonrecurring \| Minimum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights Measurement Input	0.11	0.14
Discounted cash flows \| Prepayment speed \| Fair Value, Measurements, Nonrecurring \| Maximum \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights Measurement Input	0.38	0.37
Discounted cash flows \| Prepayment speed \| Fair Value, Measurements, Nonrecurring \| Weighted Average Daily Balance \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights Measurement Input	0.13	19

Collateral-Dependent Loans, Measurement Input

No definition available.

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- Definition

Mortgage Servicing Rights

+ References

No definition available.

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- Definition

Mortgage Servicing Rights Measurement Input

+ References

No definition available.

+ Details

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
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- Definition

Value of input used to measure investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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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

No definition available.

+ Details

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- Definition

Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(b))
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- Definition

Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

+ References

+ Details

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- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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