SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Mortgage Servicing Rights (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Mortgage servicing rights
Classification of Securitizations
Fair value of capitalized mortgage servicing rights	$ 729,000,000	$ 647,000,000	$ 729,000,000	$ 647,000,000
Principal amount of loans and other financial instruments	52,000,000,000	48,000,000,000	52,000,000,000	48,000,000,000
Capitalized MSRs
Balance, at beginning of period	681,000,000	600,000,000	665,000,000	404,000,000
Originations	23,000,000	25,000,000	54,000,000	94,000,000
Changes in fair value of MSRs due to changes in inputs and assumptions	42,000,000	37,000,000	61,000,000	195,000,000
Other changes	(17,000,000)	(15,000,000)	(51,000,000)	(46,000,000)
Balance, as of September 30	729,000,000	647,000,000	729,000,000	647,000,000
MSR fees
Servicing fees	32,000,000	31,000,000	97,000,000	90,000,000
Late fees	1,000,000	1,000,000	3,000,000	3,000,000
Total MSR fees	33,000,000	32,000,000	100,000,000	93,000,000
Mortgage securitizations - Non-agency-sponsored
Classification of Securitizations
Principal securitized	600,000,000	1,100,000,000	2,900,000,000	11,300,000,000
Proceeds from new securitizations	500,000,000	1,000,000,000.0	2,600,000,000	11,000,000,000.0
Gains recognized on the securitization	50,400,000	21,000,000	64,100,000	94,000,000
Re-securitizations
Fair value of re-securitizations deals in which the entity holds a retained interest	0		0		$ 0
Mortgage securitizations - U.S. agency-sponsored
Re-securitizations
Fair value of re-securitizations deals in which the entity holds a retained interest	1,400,000,000		1,400,000,000		1,400,000,000
Securities transferred to re-securitization entities	4,300,000,000	$ 5,300,000,000	12,800,000,000	$ 20,300,000,000
Market value of retained interest related to re-securitization transaction	552,000,000		552,000,000		801,000,000
Original fair value of re-securitizations deals in which the entity holds a retained interest	85,900,000,000		$ 85,900,000,000		$ 79,400,000,000
Personal installment loan
Classification of Securitizations
Principal securitized	500,000,000
Proceeds from new securitizations	300,000,000
Gains recognized on the securitization	$ 3,700,000