ALLOWANCE FOR CREDIT LOSSES - Schedule of Allowance for Credit Losses for HTM Debt Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	$ 104	$ 85	$ 120	$ 87
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	0
Net credit losses (NCLs)	0	0	0	0
Net reserve builds (releases)	(4)	20	(21)	18
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	(4)	20	(21)	18
Other, net	(1)		0
Allowance for credit losses on HTM debt securities at end of quarter	99	105	99	105
Mortgage-backed securities
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	2	4	1	6
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	0
Net credit losses (NCLs)	0	0	0	0
Net reserve builds (releases)	3	(2)	5	(4)
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	3	(2)	5	(4)
Other, net	0		(1)
Allowance for credit losses on HTM debt securities at end of quarter	5	2	5	2
State and municipal
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	98	79	113	75
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	0
Net credit losses (NCLs)	0	0	0	0
Net reserve builds (releases)	(6)	14	(21)	18
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	(6)	14	(21)	18
Other, net	0		0
Allowance for credit losses on HTM debt securities at end of quarter	92	93	92	93
Foreign government
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	3	2	3	4
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	0
Net credit losses (NCLs)	0	0	0	0
Net reserve builds (releases)	(1)	1	(1)	(1)
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	(1)	1	(1)	(1)
Other, net	0		0
Allowance for credit losses on HTM debt securities at end of quarter	2	3	2	3
Asset- backed
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	1	0	3	2
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	0
Net credit losses (NCLs)	0	0	0	0
Net reserve builds (releases)	0	7	(4)	5
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	0	7	(4)	5
Other, net	(1)		1
Allowance for credit losses on HTM debt securities at end of quarter	$ 0	$ 7	$ 0	$ 7