FAIR VALUE MEASUREMENT - Schedule of Quantitative Information (Details) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities AFS	$ 1,072,093	$ 938,778
Fair Value, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of loans held for investment	7,108	3,468
Fair Value, Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities AFS	2,710	1,952
Fair value of loans held for investment	7,108	3,468
Fair Value, Recurring \| Level 3 \| Single Family
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of loans held for investment	$ 7,108	$ 3,468
Implied spread to benchmark interest rate curve \| Fair Value, Recurring \| Level 3 \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.0200	0.0200
Implied spread to benchmark interest rate curve \| Fair Value, Recurring \| Level 3 \| Minimum \| Single Family
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for investment, measurement input	0.0396	0.0456
Implied spread to benchmark interest rate curve \| Fair Value, Recurring \| Level 3 \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.0200	0.0200
Implied spread to benchmark interest rate curve \| Fair Value, Recurring \| Level 3 \| Maximum \| Single Family
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for investment, measurement input	0.1064	0.0687
Implied spread to benchmark interest rate curve \| Fair Value, Recurring \| Level 3 \| Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale, measurement input	0.0200	0.0200
Implied spread to benchmark interest rate curve \| Fair Value, Recurring \| Level 3 \| Weighted Average \| Single Family
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for investment, measurement input	0.0623	0.0563
Interest rate lock commitments \| Fair Value, Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net	$ 17,392	$ 2,223
Interest rate lock commitments \| Fall-out factor \| Fair Value, Recurring \| Level 3 \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net, measurement input	0.0197	0
Interest rate lock commitments \| Fall-out factor \| Fair Value, Recurring \| Level 3 \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net, measurement input	0.3838	0.5969
Interest rate lock commitments \| Fall-out factor \| Fair Value, Recurring \| Level 3 \| Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net, measurement input	0.1553	0.1220
Interest rate lock commitments \| Value of servicing \| Fair Value, Recurring \| Level 3 \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net, measurement input	0.0041	0.0055
Interest rate lock commitments \| Value of servicing \| Fair Value, Recurring \| Level 3 \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net, measurement input	0.0144	0.0177
Interest rate lock commitments \| Value of servicing \| Fair Value, Recurring \| Level 3 \| Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate lock and purchase loan commitments, net, measurement input	0.0097	0.0114

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

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-Publisher FASB
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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).

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Value of input used to measure derivative asset.

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Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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