LOANS HELD FOR INVESTMENT, NET - Past Due Status (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	$ 9,660,907	$ 9,244,661
Non-accrual	36,301	40,307
Aggregate outstanding balance	365	3,000
Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	73,912	116,696
30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	35,894	61,242
60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	1,352	12,146
Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	365	3,001
Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	9,586,995	9,127,965
Total real estate loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	8,689,230	8,294,204
Non-accrual	8,805	12,676
Total real estate loans | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	32,545	77,109
Total real estate loans | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	22,979	57,385
Total real estate loans | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	420	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	341	1,945
Total real estate loans | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	8,656,685	8,217,095
One-to-four family residential and cooperative/condominium apartment
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	691,586	669,282
Non-accrual	3,128	7,623
One-to-four family residential and cooperative/condominium apartment | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,890	13,739
One-to-four family residential and cooperative/condominium apartment | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	1	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	420	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	341	1,945
One-to-four family residential and cooperative/condominium apartment | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	687,696	655,543
Multifamily residential and residential mixed-use
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,654,164	3,356,346
Multifamily residential and residential mixed-use | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,619	34,322
Multifamily residential and residential mixed-use | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,619	30,983
Multifamily residential and residential mixed-use | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	0	3,339
Multifamily residential and residential mixed-use | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	3,650,545	3,322,024
Commercial real estate ("CRE")
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	4,091,372	3,945,948
Non-accrual	5,020	5,053
Commercial real estate ("CRE") | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	15,114	29,048
Commercial real estate ("CRE") | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	10,094	23,108
Commercial real estate ("CRE") | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	0	887
Commercial real estate ("CRE") | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	4,076,258	3,916,900
Acquisition, development, and construction
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	252,108	322,628
Non-accrual	657
Acquisition, development, and construction | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	9,922
Acquisition, development, and construction | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	9,265
Acquisition, development, and construction | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	0
Acquisition, development, and construction | Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	0
Acquisition, development, and construction | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	242,186	322,628
Commercial and Industrial ("C&I") Loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	960,888	933,559
Non-accrual	27,365	27,266
Commercial and Industrial ("C&I") Loans | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	40,240	39,115
Commercial and Industrial ("C&I") Loans | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	11,919	3,753
Commercial and Industrial ("C&I") Loans | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	932	7,040
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	24	1,056
Commercial and Industrial ("C&I") Loans | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	920,648	894,444
Other Loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	10,789	16,898
Non-accrual	131	365
Other Loans | Total Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	1,127	472
Other Loans | 30 to 59 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	996	104
Other Loans | 60 to 89 Days Past Due
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	0	3
Other Loans | Loans 90 Days or More Past Due and Still Accruing Interest
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	0
Other Loans | Current
Financing Receivable, Recorded Investment, Aging [Abstract]
Principal balances outstanding	$ 9,662	$ 16,426