ALLOWANCE FOR LOAN AND LEASE LOSSES - Schedule of Allowance for Loan and Lease Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	$ 1,747	$ 922
Initial PCD ALLL	0	200
Day 2 provision for loan and lease losses	0	462
Provision (benefit) for loan and lease losses	93	71
Total provision (benefit) for loan and lease losses	93	533
Charge-offs	(128)	(62)
Recoveries	25	12
Allowance for loan and lease losses, ending balance	1,737	1,605
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	1,126	789
Initial PCD ALLL	0	10
Day 2 provision for loan and lease losses	0	50
Provision (benefit) for loan and lease losses	59	57
Total provision (benefit) for loan and lease losses	59	107
Charge-offs	(75)	(54)
Recoveries	10	8
Allowance for loan and lease losses, ending balance	1,120	860
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	166	133
Initial PCD ALLL	0	3
Day 2 provision for loan and lease losses	0	32
Provision (benefit) for loan and lease losses	(6)	14
Total provision (benefit) for loan and lease losses	(6)	46
Charge-offs	(7)	(8)
Recoveries	2	4
Allowance for loan and lease losses, ending balance	155	178
SVB
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan and lease losses, beginning balance	455	0
Initial PCD ALLL	0	187
Day 2 provision for loan and lease losses	0	380
Provision (benefit) for loan and lease losses	40	0
Total provision (benefit) for loan and lease losses	40	380
Charge-offs	(46)	0
Recoveries	13	0
Allowance for loan and lease losses, ending balance	$ 462	$ 567