ALLOWANCE FOR LOAN AND LEASE LOSSES - Schedule of Allowance for Loan and Lease Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	$ 1,737	$ 1,605	$ 1,747	$ 922
Initial PCD ALLL	0	20	0	220
Day 2 (benefit) provision for loan and lease losses	0	0	0	462
Provision (benefit) for loan and lease losses	95	169	188	240
Total provision (benefit) for loan and lease losses	95	169	188	702
Charge-offs	(159)	(176)	(287)	(238)
Recoveries	27	19	52	31
Allowance for loan and lease losses, ending balance	1,700	1,637	1,700	1,637
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	1,120	860	1,126	789
Initial PCD ALLL	0	4	0	14
Day 2 (benefit) provision for loan and lease losses	0	(11)	0	39
Provision (benefit) for loan and lease losses	66	173	125	230
Total provision (benefit) for loan and lease losses	66	162	125	269
Charge-offs	(96)	(70)	(171)	(124)
Recoveries	13	12	23	20
Allowance for loan and lease losses, ending balance	1,103	968	1,103	968
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	155	178	166	133
Initial PCD ALLL	0	0	0	3
Day 2 (benefit) provision for loan and lease losses	0	11	0	43
Provision (benefit) for loan and lease losses	1	(13)	(5)	1
Total provision (benefit) for loan and lease losses	1	(2)	(5)	44
Charge-offs	(6)	(6)	(13)	(14)
Recoveries	3	3	5	7
Allowance for loan and lease losses, ending balance	153	173	153	173
SVB
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	462	567	455	0
Initial PCD ALLL	0	16	0	203
Day 2 (benefit) provision for loan and lease losses	0	0	0	380
Provision (benefit) for loan and lease losses	28	9	68	9
Total provision (benefit) for loan and lease losses	28	9	68	389
Charge-offs	(57)	(100)	(103)	(100)
Recoveries	11	4	24	4
Allowance for loan and lease losses, ending balance	$ 444	$ 496	$ 444	$ 496