LOANS HELD FOR INVESTMENT, NET - Past Due Status (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	$ 9,244,661	$ 5,622,044
Non-accrual	40,307	17,928
Aggregate outstanding balance	3,000	3,300
Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	116,696	37,534
30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	61,242	15,359
60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	12,146	918
Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,001	3,329
Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	9,127,965	5,584,510
Total real estate loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	8,294,204	4,978,195
Non-accrual	12,676	5,425
Total real estate loans | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	77,109	21,257
Total real estate loans | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	57,385	15,351
Total real estate loans | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	5,103
Total real estate loans | Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	1,945	481
Total real estate loans | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	8,217,095	4,956,938
One-to-four family residential and cooperative/condominium apartment
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	669,282	184,989
Non-accrual	7,623	858
One-to-four family residential and cooperative/condominium apartment | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	13,739	902
One-to-four family residential and cooperative/condominium apartment | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,294
One-to-four family residential and cooperative/condominium apartment | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	877
One-to-four family residential and cooperative/condominium apartment | Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	1,945	44
One-to-four family residential and cooperative/condominium apartment | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	655,543	184,087
Multifamily residential and residential mixed-use
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,356,346	2,758,743
Non-accrual		1,863
Multifamily residential and residential mixed-use | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	34,322	2,300
Multifamily residential and residential mixed-use | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	30,983
Multifamily residential and residential mixed-use | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,339
Multifamily residential and residential mixed-use | Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding		437
Multifamily residential and residential mixed-use | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,322,024	2,756,443
Commercial real estate ("CRE")
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,945,948	1,878,167
Non-accrual	5,053	2,704
Commercial real estate ("CRE") | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	29,048	18,055
Commercial real estate ("CRE") | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	23,108	15,351
Commercial real estate ("CRE") | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	887
Commercial real estate ("CRE") | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,916,900	1,860,112
Acquisition, development, and construction ("ADC")
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	322,628	156,296
Acquisition, development, and construction ("ADC") | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	322,628	156,296
Commercial and Industrial ("C&I") Loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	933,559	641,533
Non-accrual	27,266	12,502
Commercial and Industrial ("C&I") Loans | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	39,115	16,267
Commercial and Industrial ("C&I") Loans | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,753
Commercial and Industrial ("C&I") Loans | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	7,040	917
Commercial and Industrial ("C&I") Loans | Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	1,056	2,848
Commercial and Industrial ("C&I") Loans | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	894,444	625,266
Commercial and Industrial ("C&I") Loans | Total real estate loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding		5,619,728
Other Loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	16,898	2,316
Non-accrual	365	1
Other Loans | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	472	10
Other Loans | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	104	8
Other Loans | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3	1
Other Loans | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	$ 16,426	$ 2,306