SEGMENT INFORMATION - Significant Segment Expenses and Measure of Segment Profit or Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting, Asset Reconciling Item [Line Items]
Net interest income (expense)	$ 6,814	$ 7,143	$ 6,712
Rental income on operating lease equipment	1,096	1,048	971
All other noninterest income	1,631	1,567	11,104
Total noninterest income	2,727	2,615	12,075
Total revenue	9,541	9,758	18,787
Depreciation on operating lease equipment	398	394	371
Maintenance and other operating lease expenses	244	219	222
Personnel cost	3,294	3,078	2,636
Acquisition-related expenses	141	210	470
All other noninterest expense	1,979	1,834	1,636
Total noninterest expense	6,056	5,735	5,335
Provision for credit losses	514	431	1,375
Income (loss) before income taxes	2,971	3,592	12,077
Income tax expense	765	815	611
Net income	2,206	2,777	11,466
Loans and leases	147,930	140,221	133,302
Operating lease equipment, net	9,621	9,323	8,746
Investment securities	41,564	44,090	29,999
Deposits	161,578	155,229	145,854
Operating Segments | General Bank
Segment Reporting, Asset Reconciling Item [Line Items]
Net interest income (expense)	3,299	2,951	2,560
Rental income on operating lease equipment	0	0	0
All other noninterest income	664	612	526
Total noninterest income	664	612	526
Total revenue	3,963	3,563	3,086
Depreciation on operating lease equipment	0	0	0
Maintenance and other operating lease expenses	0	0	0
Personnel cost	838	783	734
Acquisition-related expenses	0	0	0
All other noninterest expense	1,493	1,342	1,259
Total noninterest expense	2,331	2,125	1,993
Provision for credit losses	77	135	53
Income (loss) before income taxes	1,555	1,303	1,040
Income tax expense	380	362	279
Net income	1,175	941	761
Loans and leases	64,958	64,887	61,245
Operating lease equipment, net	0	0	0
Investment securities	0	0	0
Deposits	74,796	72,956	68,507
Operating Segments | Commercial Bank
Segment Reporting, Asset Reconciling Item [Line Items]
Net interest income (expense)	3,205	3,403	2,682
Rental income on operating lease equipment	219	227	231
All other noninterest income	906	882	756
Total noninterest income	1,125	1,109	987
Total revenue	4,330	4,512	3,669
Depreciation on operating lease equipment	175	185	179
Maintenance and other operating lease expenses	0	0	0
Personnel cost	737	741	599
Acquisition-related expenses	0	0	0
All other noninterest expense	1,686	1,626	1,468
Total noninterest expense	2,598	2,552	2,246
Provision for credit losses	437	296	606
Income (loss) before income taxes	1,295	1,664	817
Income tax expense	320	442	213
Net income	975	1,222	604
Loans and leases	82,910	75,272	72,034
Operating lease equipment, net	739	750	780
Investment securities	0	0	0
Deposits	41,532	40,026	38,179
Operating Segments | Rail
Segment Reporting, Asset Reconciling Item [Line Items]
Net interest income (expense)	(213)	(186)	(141)
Rental income on operating lease equipment	877	821	740
All other noninterest income	16	14	5
Total noninterest income	893	835	745
Total revenue	680	649	604
Depreciation on operating lease equipment	223	209	192
Maintenance and other operating lease expenses	244	219	222
Personnel cost	26	25	22
Acquisition-related expenses	0	0	0
All other noninterest expense	72	59	50
Total noninterest expense	565	512	486
Provision for credit losses	0	0	0
Income (loss) before income taxes	115	137	118
Income tax expense	28	36	31
Net income	87	101	87
Loans and leases	62	62	23
Operating lease equipment, net	8,882	8,573	7,966
Investment securities	0	0	0
Deposits	2	18	13
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Net interest income (expense)	523	975	1,611
Rental income on operating lease equipment	0	0	0
All other noninterest income	45	59	9,817
Total noninterest income	45	59	9,817
Total revenue	568	1,034	11,428
Depreciation on operating lease equipment	0	0	0
Maintenance and other operating lease expenses	0	0	0
Personnel cost	1,693	1,529	1,281
Acquisition-related expenses	141	210	470
All other noninterest expense	(1,272)	(1,193)	(1,141)
Total noninterest expense	562	546	610
Provision for credit losses	0	0	716
Income (loss) before income taxes	6	488	10,102
Income tax expense	37	(25)	88
Net income	(31)	513	10,014
Loans and leases	0	0	0
Operating lease equipment, net	0	0	0
Investment securities	41,564	44,090	29,999
Deposits	$ 45,248	$ 42,229	$ 39,155