SECURED FINANCING - Repurchase Agreements - Remaining Maturities, Collateral Types and Weighted Average Rate (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Repurchase Agreements:
Netted amounts	$ 52,626,503	$ 54,769,643	[1]
Weighted Average Rate	0.41%	0.17%
Repurchase agreements, remaining maturities, percentage	0.00%
CRTs
Repurchase Agreements:
Netted amounts	$ 328,926	$ 176,450
Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	1,636,887	977,366
Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	437,269	505,001
Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	49,906,185	52,724,923
Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	317,236	385,903
1 day
Repurchase Agreements:
Netted amounts	$ 16,400,000	$ 0
Weighted Average Rate	0.32%	0.00%
1 day | CRTs
Repurchase Agreements:
Netted amounts	$ 0	$ 0
1 day | Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	0	0
1 day | Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	0	0
1 day | Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	16,400,000	0
1 day | Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	0	0
2 to 29 days
Repurchase Agreements:
Netted amounts	$ 11,027,939	$ 27,013,474
Weighted Average Rate	0.29%	0.14%
2 to 29 days | CRTs
Repurchase Agreements:
Netted amounts	$ 44,492	$ 133,525
2 to 29 days | Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	222,229	246,707
2 to 29 days | Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	0	0
2 to 29 days | Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	10,752,049	26,435,408
2 to 29 days | Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	9,169	197,834
30 to 59 days
Repurchase Agreements:
Netted amounts	$ 6,123,697	$ 10,212,453
Weighted Average Rate	0.38%	0.19%
30 to 59 days | CRTs
Repurchase Agreements:
Netted amounts	$ 0	$ 38,854
30 to 59 days | Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	235,736	270,377
30 to 59 days | Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	0	159,350
30 to 59 days | Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	5,887,961	9,743,872
30 to 59 days | Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	0	0
60 to 89 days
Repurchase Agreements:
Netted amounts	$ 10,337,224	$ 6,377,347
Weighted Average Rate	0.53%	0.17%
60 to 89 days | CRTs
Repurchase Agreements:
Netted amounts	$ 112,023	$ 4,071
60 to 89 days | Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	519,321	351,426
60 to 89 days | Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	0	0
60 to 89 days | Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	9,641,859	6,021,850
60 to 89 days | Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	64,021	0
90 to 119 days
Repurchase Agreements:
Netted amounts	$ 421,684	$ 4,824,918
Weighted Average Rate	0.32%	0.15%
90 to 119 days | CRTs
Repurchase Agreements:
Netted amounts	$ 0	$ 0
90 to 119 days | Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	72,783	12,573
90 to 119 days | Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	0	0
90 to 119 days | Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	348,901	4,812,345
90 to 119 days | Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	0	0
Over 119 days
Repurchase Agreements:
Netted amounts	$ 8,315,959	$ 6,341,451
Weighted Average Rate	0.64%	0.27%
Over 119 days | CRTs
Repurchase Agreements:
Netted amounts	$ 172,411	$ 0
Over 119 days | Non-Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	586,818	96,283
Over 119 days | Residential Mortgage Loans
Repurchase Agreements:
Netted amounts	437,269	345,651
Over 119 days | Agency Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	6,875,415	5,711,448
Over 119 days | Commercial Mortgage-Backed Securities
Repurchase Agreements:
Netted amounts	$ 244,046	$ 188,069

[1] (1)Derived from the audited consolidated financial statements at December 31, 2021.