BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 1,817	$ 850
Provision for credit losses	64	783
Net interest income after provision for credit losses	1,753	67
Noninterest income	627	10,259
Noninterest expense	1,376	855
Income before income taxes	1,004	9,471
Income tax expense (benefit)	273	(47)
Net income	731	9,518
Loans and leases	135,370	138,288	$ 133,302
Operating lease equipment, net	8,811	8,331	8,746
Deposits	149,609	140,050	$ 145,854
Operating Segments | General Bank
Segment Reporting Information [Line Items]
Net interest income (expense)	691	549
Provision for credit losses	28	10
Net interest income after provision for credit losses	663	539
Noninterest income	145	118
Noninterest expense	520	398
Income before income taxes	288	259
Income tax expense (benefit)	78	60
Net income	210	199
Loans and leases	63,732	58,101
Operating lease equipment, net	0	0
Deposits	71,150	71,117
Operating Segments | Commercial Bank
Segment Reporting Information [Line Items]
Net interest income (expense)	270	238
Provision for credit losses	14	53
Net interest income after provision for credit losses	256	185
Noninterest income	136	143
Noninterest expense	228	210
Income before income taxes	164	118
Income tax expense (benefit)	42	30
Net income	122	88
Loans and leases	31,730	28,405
Operating lease equipment, net	763	719
Deposits	3,023	3,042
Operating Segments | SVB Commercial
Segment Reporting Information [Line Items]
Net interest income (expense)	546	37
Provision for credit losses	22	0
Net interest income after provision for credit losses	524	37
Noninterest income	137	9
Noninterest expense	384	23
Income before income taxes	277	23
Income tax expense (benefit)	75	5
Net income	202	18
Loans and leases	39,846	51,702
Operating lease equipment, net	0	0
Deposits	34,014	45,328
Operating Segments | Rail
Segment Reporting Information [Line Items]
Net interest income (expense)	(43)	(28)
Provision for credit losses	0	0
Net interest income after provision for credit losses	(43)	(28)
Noninterest income	202	177
Noninterest expense	115	120
Income before income taxes	44	29
Income tax expense (benefit)	11	7
Net income	33	22
Loans and leases	62	80
Operating lease equipment, net	8,048	7,612
Deposits	14	14
Corporate
Segment Reporting Information [Line Items]
Net interest income (expense)	353	54
Provision for credit losses	0	720
Net interest income after provision for credit losses	353	(666)
Noninterest income	7	9,812
Noninterest expense	129	104
Income before income taxes	231	9,042
Income tax expense (benefit)	67	(149)
Net income	164	9,191
Loans and leases	0	0
Operating lease equipment, net	0	0
Deposits	$ 41,408	$ 20,549