SECURITIES - Summary of Residential Securities and CMBS (Details) $ in Thousands	3 Months Ended
Mar. 31, 2023 USD ($)
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance January 1, 2023	$ 65,789,907
Purchases	8,470,557
Sales	(5,261,535)
Principal paydowns	(1,348,975)
(Amortization) / accretion	(56,209)
Fair value adjustment	1,644,440
Ending balance March 31, 2023	69,238,185
Agency Securities
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance January 1, 2023	62,274,895
Purchases	8,073,778
Sales	(4,984,037)
Principal paydowns	(1,261,026)
(Amortization) / accretion	(62,270)
Fair value adjustment	1,582,194
Ending balance March 31, 2023	65,623,534
Residential Credit Securities
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance January 1, 2023	2,988,703
Purchases	372,839
Sales	(225,907)
Principal paydowns	(87,915)
(Amortization) / accretion	5,736
Fair value adjustment	60,584
Ending balance March 31, 2023	3,114,040
Commercial Securities
Debt Securities, Available-For-Sale [Roll Forward]
Beginning balance January 1, 2023	526,309
Purchases	23,940
Sales	(51,591)
Principal paydowns	(34)
(Amortization) / accretion	325
Fair value adjustment	1,662
Ending balance March 31, 2023	$ 500,611

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