Operating Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	$ 13,006	$ 13,826	$ 7,313
Allocated provision for credit losses	(813)	2,335	615
Segment net interest income after provision	13,819	11,491	6,698
Noninterest income	9,290	8,879	5,255
Amortization of intangibles	574	685	164
Other expense	595	571	542
Income before income taxes	7,993	5,473	4,019
Provision for income taxes	1,556	981	782
Net income	6,437	4,492	3,237
Identifiable assets (period end)	541,241	509,228
CB&W
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	6,738	7,379	3,633
Net income	3,235	3,043	1,736
C&CB
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	4,618	5,389	3,153
Net income	4,261	2,322	1,824
IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	100	126	146
Net income	508	407	318
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	1,550	932	381
Net income	(1,567)	(1,280)	(641)
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	13,006	13,826	7,313
Allocated provision for credit losses	(813)	2,335	615
Segment net interest income after provision	13,819	11,491	6,698
Noninterest income	9,290	8,879	5,255
Amortization of intangibles	574	685	164
Other expense	14,542	14,212	7,770
Income before income taxes	7,993	5,473	4,019
Provision for income taxes	1,556	981	782
Net income	6,437	4,492	3,237
Identifiable assets (period end)	541,241	509,228	473,078
Operating Segments | CB&W
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	8,237	8,770	4,555
Allocated provision for credit losses	150	1,003	513
Segment net interest income after provision	8,087	7,767	4,042
Noninterest income	3,865	4,071	2,317
Amortization of intangibles	317	419	58
Other expense	7,408	7,437	4,009
Income before income taxes	4,227	3,982	2,292
Provision for income taxes	992	939	556
Identifiable assets (period end)	161,126	163,725	170,034
Operating Segments | C&CB
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	4,767	5,188	2,744
Allocated provision for credit losses	(881)	1,304	102
Segment net interest income after provision	5,648	3,884	2,642
Noninterest income	3,043	2,471	1,167
Amortization of intangibles	150	175	31
Other expense	3,101	3,272	1,465
Income before income taxes	5,440	2,908	2,313
Provision for income taxes	1,179	586	489
Identifiable assets (period end)	182,338	187,196	186,462
Operating Segments | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	86	94	102
Allocated provision for credit losses	0	9	9
Segment net interest income after provision	86	85	93
Noninterest income	2,664	2,241	2,112
Amortization of intangibles	105	72	74
Other expense	1,974	1,712	1,703
Income before income taxes	671	542	428
Provision for income taxes	163	135	110
Identifiable assets (period end)	9,865	7,932	7,325
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	(84)	(226)	(88)
Allocated provision for credit losses	(82)	19	(9)
Segment net interest income after provision	(2)	(245)	(79)
Noninterest income	(282)	96	(341)
Amortization of intangibles	2	19	1
Other expense	2,059	1,791	593
Income before income taxes	(2,345)	(1,959)	(1,014)
Provision for income taxes	(778)	(679)	(373)
Identifiable assets (period end)	187,912	150,375	109,257
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	0	0	0
Intersegment Eliminations | CB&W
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	1,499	1,391	922
Intersegment Eliminations | C&CB
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	149	(201)	(409)
Intersegment Eliminations | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	(14)	(32)	(44)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	$ (1,634)	$ (1,158)	$ (469)