OFFSETTING ASSETS AND LIABILITIES - Offsetting of Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	$ 95,752	$ 20,999
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	95,752	20,999
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	(21,369)	(6,083)
Net Amount Of Assets	74,383	14,916
Payer Swaption [Member]
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	58,643	17,433
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	58,643	17,433
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	(13,962)	(3,563)
Net Amount Of Assets	44,681	13,870
TBA Contracts [Member]
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	9,456	3,559
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	9,456	3,559
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	(7,407)	(2,520)
Net Amount Of Assets	2,049	1,039
Swap [Member]
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	25,254	7
Gross Amount Of Assets Offset In The Balance Sheet	0	0
Net Amount Of Assets Presented In The Balance Sheet	25,254	7
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	0	0
Net Amount Of Assets	25,254	$ 7
Interest Rate Floor [Member]
Offsetting Assets [Line Items]
Gross Amount Of Recognized Assets	2,399
Gross Amount Of Assets Offset In The Balance Sheet	0
Net Amount Of Assets Presented In The Balance Sheet	2,399
Gross Amounts Of Financial Instruments Received Not Offset In Balance Sheet	0
Gross Amounts Of Cash Collateral Received Not Offset In Balance Sheet	0
Net Amount Of Assets	$ 2,399