SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Mortgage Servicing Rights (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Personal installment loan
Classification of Securitizations
Principal securitized	$ 300,000,000		$ 900,000,000
Proceeds from new securitizations	300,000,000		800,000,000
Gains recognized on the securitization	2,100,000		2,700,000
Mortgage servicing rights
Classification of Securitizations
Principal amount of loans and other financial instruments	58,000,000,000	$ 55,000,000,000	58,000,000,000	$ 55,000,000,000
MSR fees
Servicing fees	37,000,000	30,000,000	112,000,000	95,000,000
Late fees	1,000,000	0	2,000,000	1,000,000
Total MSR fees	38,000,000	30,000,000	114,000,000	96,000,000
Mortgage securitizations - Non-agency-sponsored
Classification of Securitizations
Principal securitized	2,900,000,000	2,700,000,000	5,700,000,000	6,800,000,000
Proceeds from new securitizations	1,600,000,000	2,700,000,000	3,900,000,000	6,400,000,000
Gains recognized on the securitization	69,200,000	44,800,000	164,800,000	126,800,000
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	2,600,000,000		2,600,000,000		1,600,000,000
Securities transferred to re-securitization entities	10,500,000,000	$ 6,300,000,000	24,100,000,000	$ 17,000,000,000
Market value of retained interest related to re-securitization transaction	1,800,000,000		1,800,000,000		977,000,000
Original fair value of re-securitizations deals in which the entity holds a retained interest	$ 78,000,000,000		$ 78,000,000,000		$ 76,800,000,000