LOANS HELD FOR INVESTMENT, NET - Loan Categories (Details) - USD ($) $ in Thousands	1 Months Ended
	Jun. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loans held for investment, net:
Total loans		$ 10,766,837	$ 10,566,831
Fair value hedge basis point adjustments		6,591
Total loans, net of fair value hedge basis point adjustments		10,773,428	10,566,831
Allowance for credit losses		(71,743)	(83,507)
Total loans held for investment, net		10,701,685	10,483,324
Total real estate loans
Loans held for investment, net:
Total loans		9,694,144	9,487,440
Total loans, net of fair value hedge basis point adjustments		9,694,144	9,487,440
Allowance for credit losses		(42,647)	(43,381)	$ (47,771)	$ (28,712)
One-to-four family residential and cooperative/condominium apartment
Loans held for investment, net:
Total loans		887,555	773,321
Total loans, net of fair value hedge basis point adjustments		887,555	773,321
Allowance for credit losses		(6,813)	(5,969)	(5,932)	(644)
Multifamily residential and residential mixed-use
Loans held for investment, net:
Total loans		4,017,176	4,026,826
Total loans, net of fair value hedge basis point adjustments		4,017,176	4,026,826
Allowance for credit losses		(7,237)	(8,360)	(7,816)	(17,016)
Commercial real estate ("CRE")
Loans held for investment, net:
Total loans		4,620,900	4,457,630
Total loans, net of fair value hedge basis point adjustments		4,620,900	4,457,630
Allowance for credit losses		(26,608)	(27,329)	(29,166)	(9,059)
Acquisition, development, and construction ("ADC")
Loans held for investment, net:
Total loans		168,513	229,663
Total loans, net of fair value hedge basis point adjustments		168,513	229,663
Allowance for credit losses		(1,989)	(1,723)	(4,857)	(1,993)
Commercial and Industrial ("C&I") Loans
Loans held for investment, net:
Total loans		1,066,938	1,071,712
Total loans, net of fair value hedge basis point adjustments		1,066,938	1,071,712
Allowance for credit losses		(28,977)	(39,853)	(35,331)	(12,737)
Commercial and Industrial ("C&I") Loans | Small Business Administration ("SBA") Paycheck Protection Program ("PPP")
Loans held for investment, net:
Total loans, net of fair value hedge basis point adjustments		1,100	5,800
Gain recorded on sale of SBA loans	$ 20,700
Sold amount	$ 596,200
Other Loans
Loans held for investment, net:
Total loans		5,755	7,679
Total loans, net of fair value hedge basis point adjustments		5,755	7,679
Allowance for credit losses		$ (119)	$ (273)	$ (751)	$ (12)