LOANS HELD FOR INVESTMENT, NET - Loans by Category Modified as TDRs (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023 USD ($) item	Sep. 30, 2023 USD ($) item	Dec. 31, 2022 USD ($) loan	Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	$ 72,563,000	$ 72,563,000	$ 83,507,000
Number of Loans	0	0	12
Pre-Modification Outstanding Recorded Investment			$ 37,463,000
Post-Modification Outstanding Recorded Investment			37,467,000
TDRs
Financing Receivable, Allowance for Credit Loss [Line Items]
Commitments to lend any additional funds on restructured loans			0
Modifications recorded investment			22,100,000
Allowance for credit losses			9,100,000
Business loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	$ 36,680,000	$ 36,680,000	$ 47,029,000	$ 39,700,000	$ 44,492,000	$ 45,128,000	$ 62,366,000
Number of Loans | loan			7
Pre-Modification Outstanding Recorded Investment			$ 21,934,000
Post-Modification Outstanding Recorded Investment			21,938,000
One-to-four family residential and cooperative/condominium apartment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	7,206,000	7,206,000	$ 5,969,000	6,419,000	5,058,000	4,514,000	5,932,000
Number of Loans | loan			2
Pre-Modification Outstanding Recorded Investment			$ 762,000
Post-Modification Outstanding Recorded Investment			762,000
Non-owner-occupied commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	18,430,000	18,430,000	$ 20,153,000	18,440,000	20,507,000	18,707,000	2,131,000
Number of Loans | loan			1
Pre-Modification Outstanding Recorded Investment			$ 991,000
Post-Modification Outstanding Recorded Investment			$ 991,000
Acquisition, development, and construction ("ADC")
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	2,338,000	2,338,000		2,558,000	3,619,000	3,788,000
Number of Loans | loan			1
Pre-Modification Outstanding Recorded Investment			$ 13,500,000
Post-Modification Outstanding Recorded Investment			13,500,000
Other Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	$ 342,000	$ 342,000	$ 273,000	$ 339,000	$ 205,000	$ 286,000	$ 751,000
Number of Loans | loan			1
Pre-Modification Outstanding Recorded Investment			$ 276,000
Post-Modification Outstanding Recorded Investment			$ 276,000