INVESTMENT SECURITIES - Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2023 USD ($) position	Dec. 31, 2022 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Book value	$ 17,466	$ 15,946
Fair value	$ 15,515	$ 14,254
Maximum individual state general bond obligation as a percentage of total debt securities (percent)	1.00%
Securities in unrealized loss positions, number of positions \| position	1,790
Securities, number of positions \| position	2,070
Standard & Poor's, AA Rating
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of debt securities considered to be of investment-grade (percent)	98.00%
Dispositions \| Gentiva Hospice
Financing Receivable, Credit Quality Indicator [Line Items]
Book value	$ 281
Fair value	$ 295

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Maximum Individual State General Bond Obligation, As Percentage Of Total Debt Securities

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Percentage Of Total Debt Securities, Investment Grade Quality

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Amortized cost of 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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Amount of 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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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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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