SECURITIES - Component of Agency Mortgage-Backed Securities Portfolio by Issuing Agency Concentration (Details) - Agency Mortgage-Backed Securities - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Mortgage-Backed Securities Portfolio [Line Items]
Total	$ 63,542,230	$ 66,308,788
Fannie Mae
Mortgage-Backed Securities Portfolio [Line Items]
Total	58,304,852	60,477,303
Freddie Mac
Mortgage-Backed Securities Portfolio [Line Items]
Total	5,185,535	5,778,809
Ginnie Mae
Mortgage-Backed Securities Portfolio [Line Items]
Total	$ 51,843	$ 52,676

The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481961/940-320-45-2

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