LOANS HELD FOR INVESTMENT, NET - Loan Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Loans held for investment, net:
Total Loans	$ 10,850,611		$ 10,566,831
Allowance for loan losses	(72,563)		(83,507)
Total loans held for investment, net	10,778,048		10,483,324
Business loans
Loans held for investment, net:
Total Loans	2,271,768		2,211,857
Allowance for loan losses	(36,680)	$ (39,700)	(47,029)	$ (44,492)	$ (45,128)	$ (62,366)
One-to-four family residential and cooperative/condominium apartment
Loans held for investment, net:
Total Loans	892,869		773,321
Allowance for loan losses	(7,206)	(6,419)	(5,969)	(5,058)	(4,514)	(5,932)
Multifamily residential and residential mixed-use
Loans held for investment, net:
Total Loans	4,102,024		4,026,826
Allowance for loan losses	(7,567)	(8,190)	(8,360)	(8,054)	(7,003)	(7,816)
Non-owner-occupied commercial real estate
Loans held for investment, net:
Total Loans	3,374,281		3,317,485
Allowance for loan losses	(18,430)	(18,440)	(20,153)	(20,507)	(18,707)	(2,131)
Non-owner-occupied commercial real estate | Total real estate loans
Loans held for investment, net:
Total Loans	3,374,281		3,317,485
Acquisition, development, and construction ("ADC")
Loans held for investment, net:
Total Loans	203,402		229,663
Allowance for loan losses	(2,338)	(2,558)		(3,619)	(3,788)
Acquisition, development, and construction ("ADC") | Total real estate loans
Loans held for investment, net:
Allowance for loan losses	(2,338)		(1,723)	(3,619)		(4,857)
Other Loans
Loans held for investment, net:
Total Loans	6,267		7,679
Allowance for loan losses	$ (342)	$ (339)	$ (273)	$ (205)	$ (286)	$ (751)