FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Schedule of Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 997,131	$ 837,499
Investment securities available for sale		838,869
Total assets measured at fair value on a nonrecurring basis		90,647
Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	998,108
Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	123,487
CMO
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	300,030	246,539
CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	300,030	246,539
FNMA MBS
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	548,738	473,987
FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	548,738	473,987
FHLMC MBS
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	112,422	87,875
FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	112,422	87,875
GNMA MBS
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	35,941	29,098
GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	35,941	29,098
Other equity investments | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		623
Other equity investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	35,083
Other Assets | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	977	747
Other Liabilities | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other liabilities	4,781	3,225
Other real estate owned | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	2,004	2,503
Loans held for sale | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	35,855	31,055
Impaired loans, net | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	50,545	57,089
Quoted Prices in Active Markets for Identical Asset (Level 1)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		623
Total assets measured at fair value on a nonrecurring basis		0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	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]
Fair Value	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]
Fair Value	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]
Fair Value	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]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other equity investments | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		623
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other equity investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other Assets | 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 Liabilities | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other liabilities	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other real estate owned | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	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]
Total assets measured at fair value on a nonrecurring basis	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Impaired loans, net | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		838,246
Total assets measured at fair value on a nonrecurring basis		31,055
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	998,108
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	35,855
Significant Other Observable Inputs (Level 2) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	300,030	246,539
Significant Other Observable Inputs (Level 2) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	548,738	473,987
Significant Other Observable Inputs (Level 2) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	112,422	87,875
Significant Other Observable Inputs (Level 2) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	35,941	29,098
Significant Other Observable Inputs (Level 2) | Other equity investments | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		0
Significant Other Observable Inputs (Level 2) | Other equity investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	0
Significant Other Observable Inputs (Level 2) | Other Assets | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	977	747
Significant Other Observable Inputs (Level 2) | Other Liabilities | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other liabilities	4,781	3,225
Significant Other Observable Inputs (Level 2) | Other real estate owned | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	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]
Total assets measured at fair value on a nonrecurring basis	35,855	31,055
Significant Other Observable Inputs (Level 2) | Impaired loans, net | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	0	0
Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		0
Total assets measured at fair value on a nonrecurring basis		59,592
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	87,632
Significant Unobservable Inputs (Level 3) | CMO | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | FNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | FHLMC MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | GNMA MBS | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Other equity investments | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities available for sale		0
Significant Unobservable Inputs (Level 3) | Other equity investments | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	35,083
Significant Unobservable Inputs (Level 3) | Other Assets | 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 Liabilities | Fair Value, Measurements, Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other liabilities	0	0
Significant Unobservable Inputs (Level 3) | Other real estate owned | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	2,004	2,503
Significant Unobservable Inputs (Level 3) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	0	0
Significant Unobservable Inputs (Level 3) | Impaired loans, net | Fair Value, Measurements, Nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 50,545	$ 57,089