LOANS HELD FOR INVESTMENT, NET - Loan Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Loans held for investment, net:
Total Loans	$ 10,116,941		$ 9,244,661
Allowance for loan losses	(81,935)	$ (79,426)	(83,853)	$ (81,255)	$ (92,760)	$ (41,461)
Total loans held for investment, net	$ 10,035,006		9,160,808
Small Business Administration ("SBA") Paycheck Protection Program ("PPP") [Member]
Loans held for investment, net:
Loan and leases carry guarantee rate	100.00%
Total real estate loans
Loans held for investment, net:
Total Loans	$ 9,195,863		8,294,204
Allowance for loan losses	(45,282)	(41,552)	(47,771)	(49,033)	(62,166)	(28,712)
One-to-four family residential and cooperative/condominium apartment
Loans held for investment, net:
Total Loans	722,081		669,282
Allowance for loan losses	(5,058)	(4,514)	(5,932)	(6,104)	(5,522)	(644)
Multifamily residential and residential mixed-use
Loans held for investment, net:
Total Loans	3,968,244		3,356,346
Allowance for loan losses	(8,054)	(7,003)	(7,816)	(8,307)	(10,285)	(17,016)
Commercial real estate ("CRE")
Loans held for investment, net:
Total Loans	4,264,519		3,945,948
Allowance for loan losses	(28,551)	(26,247)	(29,166)	(29,603)	(41,201)	(9,059)
Acquisition, development, and construction
Loans held for investment, net:
Total Loans	241,019		322,628
Allowance for loan losses	(3,619)	(3,788)	(4,857)	(5,019)	(5,158)	(1,993)
Commercial and Industrial ("C&I") Loans
Loans held for investment, net:
Total Loans	912,151		933,559
Allowance for loan losses	(36,448)	(37,588)	(35,331)	(31,545)	(30,095)	(12,737)
Commercial and Industrial ("C&I") Loans | Small Business Administration ("SBA") Paycheck Protection Program ("PPP") [Member]
Loans held for investment, net:
Total Loans	11,400		66,000
Other Loans
Loans held for investment, net:
Total Loans	8,927		16,898
Allowance for loan losses	$ (205)	$ (286)	$ (751)	$ (677)	$ (499)	$ (12)