LOANS HELD FOR INVESTMENT, NET - Allowance for Credit Losses Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance			$ 83,507
(Recovery) provision for credit losses	$ 1,806	$ 6,587	(950)	$ 5,039
Charge-offs			(10,937)		$ (11,401)
Allowance for credit losses, Ending balance	72,563		72,563		83,507
Non-accrual with No Allowance	3,809		3,809		6,075
Non-accrual with Allowance	19,511		19,511		28,162
Reserve	14,744		14,744		22,389
Interest income on non-accrual loans held for investment
Interest income on non-accrual loans	0	0	0	0
Business loans
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	39,700	45,128	47,029	62,366	62,366
(Recovery) provision for credit losses	1,822	3,246	(328)	(10,799)
Charge-offs	(5,147)	(5,462)	(10,921)	(8,742)	(11,401)
Recoveries	305	1,580	900	1,667
Allowance for credit losses, Ending balance	36,680	44,492	36,680	44,492	47,029
Non-accrual with No Allowance	3,809		3,809		5,403
Non-accrual with Allowance	15,746		15,746		22,384
Reserve	14,065		14,065		20,812
One-to-four family residential and cooperative/condominium apartment
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	6,419	4,514	5,969	5,932	5,932
(Recovery) provision for credit losses	787	544	1,251	(874)
Charge-offs			(14)
Allowance for credit losses, Ending balance	7,206	5,058	7,206	5,058	5,969
Non-accrual with Allowance	2,874		2,874		3,203
Reserve	140		140		181
Multifamily residential and residential mixed-use
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	8,190	7,003	8,360	7,816	7,816
(Recovery) provision for credit losses	(621)	1,051	(791)	236
Charge-offs	(2)		(2)
Recoveries				2
Allowance for credit losses, Ending balance	7,567	8,054	7,567	8,054	8,360
Non-owner-occupied commercial real estate
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	18,440	18,707	20,153	2,131	2,131
(Recovery) provision for credit losses	(10)	1,800	(1,723)	18,322
Recoveries				54
Allowance for credit losses, Ending balance	18,430	20,507	18,430	20,507	20,153
Non-accrual with No Allowance					15
Non-accrual with Allowance	15		15		2,476
Reserve	15		15		1,297
Acquisition, development, and construction ("ADC")
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	2,558	3,788
(Recovery) provision for credit losses	(220)	(169)
Allowance for credit losses, Ending balance	2,338	3,619	2,338	3,619
Non-accrual with No Allowance					657
Non-accrual with Allowance	657		657
Reserve	305		305
Acquisition, development, and construction ("ADC") | Total real estate loans
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance			1,723	4,857	4,857
(Recovery) provision for credit losses			615	(1,238)
Allowance for credit losses, Ending balance	2,338	3,619	2,338	3,619	1,723
Other Loans
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	339	286	273	751	751
(Recovery) provision for credit losses	23	(32)	116	(495)
Charge-offs	(26)	(49)	(60)	(52)
Recoveries	6		13	1
Allowance for credit losses, Ending balance	342	205	342	205	273
Non-accrual with Allowance	219		219		99
Reserve	219		219		99
Includes other loans
Allowance for loan losses [Roll Forward]
Allowance for credit losses, Beginning balance	75,646	79,426	83,507	83,853	83,853
(Recovery) provision for credit losses	1,781	6,440	(860)	5,152
Charge-offs	(5,175)	(5,511)	(10,997)	(8,794)
Recoveries	311	1,580	913	1,724
Allowance for credit losses, Ending balance	$ 72,563	$ 81,935	$ 72,563	$ 81,935	$ 83,507