LOANS HELD FOR INVESTMENT, NET - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2020
Unpaid Principal Balance
With no related allowance recorded			$ 4,567
With related allowance recorded			12,502
Total			17,069
Recorded Investment
With no related allowance recorded			4,567
With related allowance recorded			12,502
Total			17,069
Related Allowance
Impaired Financing Receivable, Related Allowance			6,474
Average Recorded Investment
With no related allowance recorded	$ 2,820	$ 3,114
Total	13,052	10,614
Interest Income Recognized
With no related allowance recorded		65
Total		218
One-to-four family residential and cooperative/condominium apartment
Unpaid Principal Balance
With no related allowance recorded			1,863
Recorded Investment
With no related allowance recorded			1,863
Related Allowance
Impaired Financing Receivable, Related Allowance			0
Average Recorded Investment
With no related allowance recorded		10
Interest Income Recognized
With no related allowance recorded		4
Multifamily residential and residential mixed-use
Average Recorded Investment
With no related allowance recorded	1,295	416
Interest Income Recognized
With no related allowance recorded		7
Commercial real estate ("CRE")
Unpaid Principal Balance
With no related allowance recorded			2,704
Recorded Investment
With no related allowance recorded			2,704
Related Allowance
Impaired Financing Receivable, Related Allowance			0
Average Recorded Investment
With no related allowance recorded	1,525	2,688
Interest Income Recognized
With no related allowance recorded		54
Commercial and Industrial ("C&I") Loans
Unpaid Principal Balance
With related allowance recorded			12,502
Recorded Investment
With related allowance recorded			12,502
Related Allowance
Impaired Financing Receivable, Related Allowance			$ 6,474
Average Recorded Investment
With related allowance recorded	$ 10,232	7,500
Interest Income Recognized
With related allowance recorded		$ 153