FAIR VALUE DISCLOSURES OF FINANCIAL ASSETS AND LIABILITIES - Schedule of Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	$ 5,495,929	$ 5,205,311
Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Other assets	72,461	5,153
Liabilities measured at fair value on a recurring basis:
Other liabilities	89,148	23,291
Assets measured at fair value on a nonrecurring basis:
Total assets	5,568,390	5,210,464
Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other real estate owned	1,818	2,320
Total assets	86,086	126,187
CMO
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	563,090	575,766
CMO | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	563,090	575,766
FNMA MBS
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	4,586,978	4,245,684
FNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	4,586,978	4,245,684
FHLMC MBS
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	126,406	145,528
FHLMC MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	126,406	145,528
GNMA MBS
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	16,059	17,936
GNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	16,059	17,936
GSE agency notes
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	203,396	220,397
GSE agency notes | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	203,396	220,397
Other investments | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other investments	13,651	10,518
Loans held for sale | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Loans, held for sale	70,617	113,349
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Other assets	0	0
Liabilities measured at fair value on a recurring basis:
Other liabilities	0	0
Assets measured at fair value on a nonrecurring basis:
Total assets	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
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
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | FNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | FHLMC MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | GNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | GSE agency notes | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Other investments | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other investments	0	0
Quoted Prices in Active Markets for Identical Asset (Level 1) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Loans, held for sale	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Other assets	72,252	5,153
Liabilities measured at fair value on a recurring basis:
Other liabilities	70,516	3,039
Assets measured at fair value on a nonrecurring basis:
Total assets	5,568,181	5,210,464
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other real estate owned	0	0
Total assets	70,617	113,349
Significant Other Observable Inputs (Level 2) | CMO | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	563,090	575,766
Significant Other Observable Inputs (Level 2) | FNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	4,586,978	4,245,684
Significant Other Observable Inputs (Level 2) | FHLMC MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	126,406	145,528
Significant Other Observable Inputs (Level 2) | GNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	16,059	17,936
Significant Other Observable Inputs (Level 2) | GSE agency notes | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	203,396	220,397
Significant Other Observable Inputs (Level 2) | Other investments | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other investments	0	0
Significant Other Observable Inputs (Level 2) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Loans, held for sale	70,617	113,349
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Other assets	209	0
Liabilities measured at fair value on a recurring basis:
Other liabilities	18,632	20,252
Assets measured at fair value on a nonrecurring basis:
Total assets	209	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other real estate owned	1,818	2,320
Total assets	15,469	12,838
Significant Unobservable Inputs (Level 3) | CMO | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | FNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | FHLMC MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | GNMA MBS | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | GSE agency notes | Fair Value, Measurements, Recurring
Assets measured at fair value on a recurring basis:
Investment securities available-for-sale	0	0
Significant Unobservable Inputs (Level 3) | Other investments | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Other investments	13,651	10,518
Significant Unobservable Inputs (Level 3) | Loans held for sale | Fair Value, Measurements, Nonrecurring
Assets measured at fair value on a nonrecurring basis:
Loans, held for sale	$ 0	$ 0