Business Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 2,946	$ 1,390	$ 1,388
Provision (benefit) for credit losses	645	(37)	58
Net interest income after provision for credit losses	2,301	1,427	1,330
Noninterest income	2,136	508	477
Income before income taxes	1,362	701	618
Income tax expense (benefit)	264	154	126
Net income	1,098	547	492
Loans and leases	70,781	32,372	32,792
Deposits	89,408	51,406	43,432
Operating lease equipment, net	8,156	0
Operating Segments | General Banking
Segment Reporting Information [Line Items]
Net interest income (expense)	1,942	1,447	1,391
Provision (benefit) for credit losses	11	(37)	58
Net interest income after provision for credit losses	1,931	1,484	1,333
Noninterest income	472	433	379
Noninterest expense	1,570	1,179	1,146
Income before income taxes	833	738	566
Income tax expense (benefit)	204	162	116
Net income	629	576	450
Loans and leases	42,930	31,820	32,235
Deposits	84,361	51,344	43,391
Operating lease equipment, net	0
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income (expense)	889	17	15
Provision (benefit) for credit losses	121	0	0
Net interest income after provision for credit losses	768	17	15
Noninterest income	521	0	0
Noninterest expense	746	3	3
Income before income taxes	543	14	12
Income tax expense (benefit)	128	3	2
Net income	415	11	10
Loans and leases	27,773	552	554
Deposits	3,225	62	40
Operating lease equipment, net	723
Operating Segments | Rail
Segment Reporting Information [Line Items]
Net interest income (expense)	(80)	0	0
Provision (benefit) for credit losses	0	0	0
Net interest income after provision for credit losses	(80)	0	0
Noninterest income	657	0	0
Noninterest expense	428	0	0
Income before income taxes	149	0	0
Income tax expense (benefit)	37	0	0
Net income	112	0	0
Loans and leases	78	0	0
Deposits	15	0	0
Operating lease equipment, net	7,433
Corporate
Segment Reporting Information [Line Items]
Net interest income (expense)	195	(74)	(18)
Provision (benefit) for credit losses	513	0	0
Net interest income after provision for credit losses	(318)	(74)	(18)
Noninterest income	486	75	98
Noninterest expense	331	52	40
Income before income taxes	(163)	(51)	40
Income tax expense (benefit)	(105)	(11)	8
Net income	(58)	(40)	32
Loans and leases	0	0	3
Deposits	1,807	$ 0	$ 1
Operating lease equipment, net	$ 0