LOANS HELD FOR INVESTMENT, NET - Loan Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Loans held for investment, net:
Total	$ 10,886,387		$ 10,766,837
Fair value hedge basis point adjustments	5,657		6,591
Total loans, net of fair value hedge basis point adjustments	10,892,044		10,773,428
Allowance for credit losses	(85,221)		(71,743)
Total loans held for investment, net	10,806,823		10,701,685
Business Loans
Loans held for investment, net:
Total	2,651,729		2,308,171
Allowance for credit losses	(45,026)	$ (37,115)	(35,962)	$ (36,680)	$ (39,700)	$ (47,029)
One-to-Four Family Residential and Cooperative/Condominium Apartment
Loans held for investment, net:
Total	932,767		887,555
Allowance for credit losses	(8,646)	(7,305)	(6,813)	(7,206)	(6,419)	(5,969)
Multifamily Residential and Residential Mixed-Use
Loans held for investment, net:
Total	3,866,478		4,017,176
Allowance for credit losses	(12,503)	(12,357)	(7,237)	(7,567)	(8,190)	(8,360)
Non-Owner-Occupied Commercial Real Estate
Loans held for investment, net:
Total	3,280,056		3,379,667
Allowance for credit losses	(16,302)	(18,340)	(19,623)	(18,430)	(18,440)	(20,153)
Acquisition, development, and construction ("ADC")
Loans held for investment, net:
Total	149,299		168,513
Allowance for credit losses	(2,521)	(2,455)	(1,989)	(2,338)	(2,558)	(1,723)
Other Loans
Loans held for investment, net:
Total	6,058		5,755
Allowance for credit losses	$ (223)	$ (240)	$ (119)	$ (342)	$ (339)	$ (273)