Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		$ 3,868	$ 3,183
Allocated provision for credit losses		502	(95)
Segment net interest income after provision		3,366	3,278
Noninterest income		2,234	2,142
Amortization of intangibles		136	137
Other expense		291	182
Income before income taxes		1,909	1,746
Provision for income taxes		394	330
Net income		1,515	1,416
Identifiable assets (period end)		574,354		$ 555,255
CB&W
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1,601	1,528
C&CB
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		2,308	1,118
IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1	1
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	[1]	(42)	536
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		3,868	3,183
Allocated provision for credit losses		502	(95)
Segment net interest income after provision		3,366	3,278
Noninterest income		2,234	2,142
Amortization of intangibles		136	137
Other expense		3,555	3,537
Income before income taxes		1,909	1,746
Provision for income taxes		394	330
Net income		1,515	1,416
Identifiable assets (period end)		574,354	543,979
Operating Segments | CB&W
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		2,740	2,184
Allocated provision for credit losses		274	74
Segment net interest income after provision		2,466	2,110
Noninterest income		873	910
Amortization of intangibles		69	73
Other expense		1,900	1,812
Income before income taxes		1,370	1,135
Provision for income taxes		326	274
Net income		1,044	861
Identifiable assets (period end)		168,701	159,939
Operating Segments | C&CB
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1,752	1,289
Allocated provision for credit losses		232	(150)
Segment net interest income after provision		1,520	1,439
Noninterest income		630	656
Amortization of intangibles		31	33
Other expense		812	755
Income before income taxes		1,307	1,307
Provision for income taxes		273	284
Net income		1,034	1,023
Identifiable assets (period end)		213,143	188,806
Operating Segments | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		14	3
Allocated provision for credit losses		0	0
Segment net interest income after provision		14	3
Noninterest income		817	733
Amortization of intangibles		36	30
Other expense		648	516
Income before income taxes		147	190
Provision for income taxes		36	47
Net income		111	143
Identifiable assets (period end)		7,263	6,494
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	[1]	(638)	(293)
Allocated provision for credit losses	[1]	(4)	(19)
Segment net interest income after provision	[1]	(634)	(274)
Noninterest income	[1]	(86)	(157)
Amortization of intangibles		0	1
Other expense	[1]	195	454
Income before income taxes	[1]	(915)	(886)
Provision for income taxes	[1]	(241)	(275)
Net income	[1]	(674)	(611)
Identifiable assets (period end)	[1]	185,247	188,740
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		0	0
Intersegment Eliminations | CB&W
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1,139	656
Intersegment Eliminations | C&CB
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		(556)	171
Intersegment Eliminations | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		13	2
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	[1]	$ (596)	$ (829)

[1] Includes financial data from business units below the quantitative and qualitative thresholds requiring disclosure.