FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Schedule of Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	$ 2,048,400	$ 1,944,914
Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other assets	12,364	4,884
Other liabilities	9,325	3,918
Total assets	2,060,764	1,949,798
Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	4,825	2,605
Total assets	160,997	156,523
CMO
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	333,398	340,230
CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	333,398	340,230
FNMA MBS
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	1,361,664	1,242,453
FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	1,361,664	1,242,453
FHLMC MBS
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	320,046	328,946
FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	320,046	328,946
GNMA MBS
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	33,292	33,285
GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	33,292	33,285
Other investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	70,714	70,046
Loans held for sale | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-sale	85,458	83,872
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other assets	0	0
Other liabilities	0	0
Total assets	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	0	0
Total assets	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-sale	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other assets	12,364	4,884
Other liabilities	9,325	3,918
Total assets	2,060,764	1,949,798
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	0	0
Total assets	85,458	83,872
Significant Other Observable Inputs (Level 2) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	333,398	340,230
Significant Other Observable Inputs (Level 2) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	1,361,664	1,242,453
Significant Other Observable Inputs (Level 2) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	320,046	328,946
Significant Other Observable Inputs (Level 2) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	33,292	33,285
Significant Other Observable Inputs (Level 2) | Other investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	0	0
Significant Other Observable Inputs (Level 2) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-sale	85,458	83,872
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other assets	0	0
Other liabilities	0	0
Total assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	4,825	2,605
Total assets	75,539	72,651
Significant Unobservable Inputs (Level 3) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | Other investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other investments	70,714	70,046
Significant Unobservable Inputs (Level 3) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held-for-sale	$ 0	$ 0