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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	$ 85	$ 78	$ 87	$ 86
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	3
Net credit losses (NCLs)	0	0	0	3
Net reserve builds (releases)	20	4	18	(4)
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	20	4	18	(7)
Other, net		1		1
Allowance for credit losses on HTM debt securities at end of quarter	105	83	105	83
Mortgage-backed securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	4	4	6	3
Gross credit losses	0	0	0	0
Gross recoveries	0	0	0	3
Net credit losses (NCLs)	0	0	0	3
Net reserve builds (releases)	(2)	1	(4)	2
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	(2)	1	(4)	(1)
Other, net		0		0
Allowance for credit losses on HTM debt securities at end of quarter	2	5	2	5
State and municipal
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	79	69	75	74
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)	14	3	18	(2)
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	14	3	18	(2)
Other, net		0		0
Allowance for credit losses on HTM debt securities at end of quarter	93	72	93	72
Foreign government
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	2	5	4	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)	1	0	(1)	(1)
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	1	0	(1)	(1)
Other, net		0		0
Allowance for credit losses on HTM debt securities at end of quarter	3	5	3	5
Asset-backed
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses on HTM debt securities at beginning of quarter	0	0	2	3
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)	7	0	5	(3)
Net specific reserve builds (releases)	0	0	0	0
Total provision for credit losses on HTM debt securities	7	0	5	(3)
Other, net		1		1
Allowance for credit losses on HTM debt securities at end of quarter	$ 7	$ 1	$ 7	$ 1