SECURITIES - Narrative (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Accrued interest receivable on debt securities	$ 56,000,000		$ 55,000,000
Taxable interest income from securities	128,000,000	$ 147,000,000
Offsetting of short-term receivables or payables recognized	0		$ 0
Purchases of debt securities available for sale	$ 4,256,000,000	2,102,000,000
Held-to-maturity, zero expected credit loss, percent of portfolio	71.00%
Held-to-maturity, expected credit loss, percent of portfolio	29.00%
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Securitizations of mortgage loans	$ 81,000,000	$ 0

Debt Securities, Held To Maturity, Expected Credit Loss, Percent Of Portfolio

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Debt Securities, Held To Maturity, Zero Expected Credit Loss, Percent Of Portfolio

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- Definition

Debt Securities, Interest Receivable

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- Definition

Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.9-04.2)
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Amount of cash outflow to acquire investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

The cash inflow from securitizing loans held with the intention to resell in the near future.

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-Name Accounting Standards Codification
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, before effects of master netting arrangements, of securities loaned to entities in exchange for collateral and funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

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