LOANS HELD FOR INVESTMENT, NET - Deferral Loans (Details) $ in Thousands	Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($)
CARES Act Loan [Abstract]
Principal balances outstanding	$ 9,244,661	$ 5,622,044
COVID-19 [Member]
CARES Act Loan [Abstract]
Number of loans | loan	7
Principal balances outstanding	$ 5,660
% of portfolio	0.10%
One-to-four family residential and cooperative/condominium apartment
CARES Act Loan [Abstract]
Principal balances outstanding	$ 669,282	184,989
One-to-four family residential and cooperative/condominium apartment | COVID-19 [Member]
CARES Act Loan [Abstract]
Number of loans | loan	5
Principal balances outstanding	$ 1,922
% of portfolio	0.30%
Commercial real estate ("CRE")
CARES Act Loan [Abstract]
Principal balances outstanding	$ 3,945,948	1,878,167
Commercial real estate ("CRE") | COVID-19 [Member]
CARES Act Loan [Abstract]
Number of loans | loan	1
Principal balances outstanding	$ 3,487
% of portfolio	0.10%
Commercial and Industrial ("C&I") Loans
CARES Act Loan [Abstract]
Principal balances outstanding	$ 933,559	$ 641,533
Commercial and Industrial ("C&I") Loans | COVID-19 [Member]
CARES Act Loan [Abstract]
Number of loans | loan	1
Principal balances outstanding	$ 251