Business Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 6,712	$ 2,946	$ 1,390
Provision for credit losses	1,375	645	(37)
Net interest income after provision for credit losses	5,337	2,301	1,427
Noninterest income	12,075	2,136	508
Noninterest expense	5,335	3,075	1,234
Income before income taxes	12,077	1,362	701
Income tax expense (benefit)	611	264	154
Net income	11,466	1,098	547
Total assets	213,758	109,298	58,309
Loans and leases	133,302	70,781	32,372
Operating lease equipment, net	8,746	8,156
Deposits	145,854	89,408	51,406
Operating Segments | General Banking
Segment Reporting Information [Line Items]
Net interest income (expense)	2,433	1,947	1,447
Provision for credit losses	71	11	(37)
Net interest income after provision for credit losses	2,362	1,936	1,484
Noninterest income	490	482	433
Noninterest expense	1,607	1,542	1,179
Income before income taxes	1,245	876	738
Income tax expense (benefit)	336	214	162
Net income	909	662	576
Total assets	50,179	45,802	33,848
Loans and leases	47,330	43,212	31,820
Operating lease equipment, net	0	0
Deposits	102,647	84,369	51,344
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income (expense)	1,015	884	17
Provision for credit losses	517	121	0
Net interest income after provision for credit losses	498	763	17
Noninterest income	559	517	0
Noninterest expense	823	744	3
Income before income taxes	234	536	14
Income tax expense (benefit)	69	128	3
Net income	165	408	11
Total assets	31,826	28,235	552
Loans and leases	30,936	27,491	552
Operating lease equipment, net	780	723
Deposits	3,228	3,219	62
Operating Segments | Silicon Valley Banking
Segment Reporting Information [Line Items]
Net interest income (expense)	1,946	0	0
Provision for credit losses	71	0	0
Net interest income after provision for credit losses	1,875	0	0
Noninterest income	478	0	0
Noninterest expense	1,642	0	0
Income before income taxes	711	0	0
Income tax expense (benefit)	181	0	0
Net income	530	0	0
Total assets	56,190	0	0
Loans and leases	55,013	0	0
Operating lease equipment, net	0	0
Deposits	38,477	0	0
Operating Segments | Rail
Segment Reporting Information [Line Items]
Net interest income (expense)	(143)	(80)	0
Provision for credit losses	0	0	0
Net interest income after provision for credit losses	(143)	(80)	0
Noninterest income	746	657	0
Noninterest expense	481	428	0
Income before income taxes	122	149	0
Income tax expense (benefit)	32	37	0
Net income	90	112	0
Total assets	8,199	7,647	0
Loans and leases	23	78	0
Operating lease equipment, net	7,966	7,433
Deposits	13	15	0
Corporate
Segment Reporting Information [Line Items]
Net interest income (expense)	1,461	195	(74)
Provision for credit losses	716	513	0
Net interest income after provision for credit losses	745	(318)	(74)
Noninterest income	9,802	480	75
Noninterest expense	782	361	52
Income before income taxes	9,765	(199)	(51)
Income tax expense (benefit)	(7)	(115)	(11)
Net income	9,772	(84)	(40)
Total assets	67,364	27,614	23,909
Loans and leases	0	0	0
Operating lease equipment, net	0	0
Deposits	$ 1,489	$ 1,805	$ 0