LOANS HELD FOR INVESTMENT, NET - Collateral Dependent Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	$ 10,876,415		$ 10,566,831
Allowance for credit losses	75,646		83,507
Real Estate Collateral Dependent | Total real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	6,254		8,997
Allowance for credit losses	305		1,297
Business Loan Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	2,250,108		2,211,857
Allowance for credit losses	39,700	$ 43,879	47,029	$ 45,128	$ 43,728	$ 62,366
Business Loan Portfolio Segment [Member] | Real Estate Collateral Dependent
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	5,597		5,849
One-to-four family residential and cooperative/condominium apartment
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	855,980		773,321
Allowance for credit losses	6,419	6,012	5,969	4,514	4,528	5,932
Multifamily residential and residential mixed-use
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	4,132,358		4,026,826
Allowance for credit losses	8,190	7,613	8,360	7,003	7,061	7,816
Non-owner Occupied Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	3,406,232		3,317,485
Allowance for credit losses	18,440	18,076	20,153	18,707	19,180	2,131
Non-owner Occupied Commercial Real Estate Portfolio Segment [Member] | Total real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	3,406,232		3,317,485
Non-owner Occupied Commercial Real Estate Portfolio Segment [Member] | Real Estate Collateral Dependent
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans			2,491
Allowance for credit losses			1,297
Acquisition, development, and construction ("ADC")
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	225,580		229,663
Allowance for credit losses	2,558	2,515		3,788	4,758
Acquisition, development, and construction ("ADC") | Total real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses	2,558		1,723	3,788		4,857
Acquisition, development, and construction ("ADC") | Real Estate Collateral Dependent
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	657		657
Allowance for credit losses	305
Other Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	6,157		7,679
Allowance for credit losses	$ 339	$ 240	$ 273	$ 286	$ 360	$ 751