SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Mortgage Servicing Rights (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Mortgage servicing rights
Classification of Securitizations
Fair value of capitalized mortgage servicing rights	$ 600,000,000	$ 419,000,000	$ 600,000,000	$ 419,000,000
Principal amount of loans and other financial instruments	49,000,000,000	50,000,000,000	49,000,000,000	50,000,000,000
Capitalized MSRs
Balance, at beginning of period	520,000,000	433,000,000	404,000,000	336,000,000
Originations	35,000,000	25,000,000	69,000,000	68,000,000
Changes in fair value of MSRs due to changes in inputs and assumptions	59,000,000	(21,000,000)	158,000,000	52,000,000
Other changes	(14,000,000)	(18,000,000)	(31,000,000)	(37,000,000)
Sale of MSRs	0	0	0	0
Balance, as of June 30	600,000,000	419,000,000	600,000,000	419,000,000
MSR fees
Servicing fees	30,000,000	37,000,000	59,000,000	68,000,000
Late fees	1,000,000	0	2,000,000	1,000,000
Ancillary fees	0	0	0	0
Total MSR fees	31,000,000	37,000,000	61,000,000	69,000,000
Mortgage securitizations - Non-agency-sponsored
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	1,500,000,000		1,500,000,000		1,200,000,000
Securities transferred to re-securitization entities	5,600,000,000	$ 11,400,000,000	14,900,000,000	$ 24,500,000,000
Market value of retained interest related to re-securitization transaction	656,000,000		656,000,000		641,000,000
Original fair value of re-securitizations deals in which the entity holds a retained interest	$ 78,800,000,000		$ 78,800,000,000		$ 78,400,000,000