SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
MSR fees
Servicing fees, location	Commissions and fees	Commissions and fees	Commissions and fees
Mortgage servicing rights
Classification of Securitizations
Fair value of capitalized mortgage servicing rights	$ 691.0	$ 665.0
Principal amount of loans and other financial instruments	52,000.0	51,000.0
Capitalized MSRs
Balance at beginning of period	665.0	404.0
Originations	66.0	120.0
Changes in fair value of MSRs due to changes in inputs and assumptions	28.0	201.0
Other changes	(68.0)	(60.0)
Balance at end of period	691.0	665.0	$ 404.0
MSR fees
Servicing fees	129.0	122.0	131.0
Late fees	4.0	4.0	3.0
Total MSR fees	133.0	126.0	134.0
Mortgage securitizations - Non-agency-sponsored
Classification of Securitizations
Principal securitized	4,800.0	13,900.0	25,200.0
Proceeds from new securitizations	3,500.0	13,400.0	$ 25,400.0
Mortgage-backed securities - U.S. agency-sponsored
Re-securitizations
Securities transferred to re-securitization entities	17,100.0	24,100.0
Fair value of re-securitizations deals in which the entity holds a retained interest	1,700.0	1,400.0
Market value of retained interest related to re-securitization transaction	930.0	801.0
Original fair value of re-securitizations deals in which the entity holds a retained interest	84,100.0	$ 79,400.0
Consumer
Classification of Securitizations
Principal securitized	1,000.0
Proceeds from new securitizations	700.0
Gains recognized on the securitization	$ 7.5

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Continuing Involvement with Transferred Financial Assets, Principal Amount Securitized During Period

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Represents the fair value of capitalized mortgage servicing rights.

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Represents the fair value of re-securitizations deals in which entity holds retained interest.

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This element represents the amount of market value of interest owned by the entity in private-label re-securitization entities, for current period.

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Re-securitizations [Abstract]

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Represents the amount of securities transferred to re-securitization entities.

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Cash Flows between a transferor and a transferee attributable to newly transferred assets related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

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Indicates line item in statement of income or comprehensive income that includes contractually specified servicing fee income.

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All amounts that, per contract, are due to the servicer in exchange for servicing the financial asset and would no longer be received by a servicer if the beneficial owners of the serviced assets (or their trustees or agents) were to exercise their actual or potential authority under the contract to shift the servicing to another servicer. Depending on the servicing contract, those fees may include some or all of the difference between the interest rate collected on the asset being serviced and the rate to be paid to the beneficial owners of the asset.

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Income from mortgage banking activities (fees and commissions) and servicing real estate mortgages, credit cards, and other financial assets held by others net of any related impairment of capitalized service costs. Also includes any premiums received in lieu of regular servicing fees on such loans only as earned over the life of the loans.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher SEC

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A gain (loss) realized on a transfer, accounted for as a sale, of all or a portion of financial assets in which the transferor surrenders control and receives consideration other than a beneficial interest in the assets transferred. Reflects the amount of sales proceeds in excess of, or deficient from, the sum of the carrying amounts of transferred financial assets plus transaction costs.

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All amounts that are due to the servicer of a financial asset as a result of the debt holder not meeting the monthly payment terms.

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Amount of transferred financial assets in which the transferor has continuing involvement with the assets underlying the transaction that continue to be recognized in the statement of financial position. Includes, but is not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets.

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The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of increase (decrease) in fair value from changes in the inputs, assumptions, or model used to calculate the fair value of the contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Amount of increase (decrease) in fair value from changes classified as other for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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