Operating Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	$ 7,313	$ 6,682	$ 6,535
Allocated provision for credit losses	615	566	547
Segment net interest income after provision	6,698	6,116	5,988
Noninterest income	5,255	4,876	4,782
Noninterest expense	7,934	6,932	7,444
Income before income taxes	4,019	4,060	3,326
Provision for income taxes	782	803	911
Net income	3,237	3,257	2,415
Identifiable assets (period end)	473,078	225,697
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	3,633	3,410	3,401
Net income	1,712	1,488	1,070
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	3,153	2,723	2,332
Net income	1,841	1,546	1,170
IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	146	119	98
Net income	319	253	161
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	381	430	704
Net income	(635)	(30)	14
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	7,313	6,682	6,535
Allocated provision for credit losses	615	566	547
Segment net interest income after provision	6,698	6,116	5,988
Noninterest income	5,255	4,876	4,782
Noninterest expense	7,934	6,932	7,444
Income before income taxes	4,019	4,060	3,326
Provision for income taxes	782	803	911
Net income	3,237	3,257	2,415
Identifiable assets (period end)	473,078	225,697	221,642
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	4,546	3,969	3,775
Allocated provision for credit losses	513	506	504
Segment net interest income after provision	4,033	3,463	3,271
Noninterest income	2,313	2,152	2,109
Noninterest expense	4,086	3,637	3,671
Income before income taxes	2,260	1,978	1,709
Provision for income taxes	548	490	639
Identifiable assets (period end)	170,059	74,974	72,311
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	2,760	2,458	2,341
Allocated provision for credit losses	102	111	49
Segment net interest income after provision	2,658	2,347	2,292
Noninterest income	1,086	925	911
Noninterest expense	1,499	1,309	1,462
Income before income taxes	2,245	1,963	1,741
Provision for income taxes	404	417	571
Identifiable assets (period end)	185,859	86,005	83,290
Operating Segments | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	103	87	77
Allocated provision for credit losses	9	3	3
Segment net interest income after provision	94	84	74
Noninterest income	2,112	1,872	1,778
Noninterest expense	1,777	1,615	1,593
Income before income taxes	429	341	259
Provision for income taxes	110	88	98
Identifiable assets (period end)	7,325	6,622	6,024
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	(96)	168	342
Allocated provision for credit losses	(9)	(54)	(9)
Segment net interest income after provision	(87)	222	351
Noninterest income	(256)	(73)	(16)
Noninterest expense	572	371	718
Income before income taxes	(915)	(222)	(383)
Provision for income taxes	(280)	(192)	(397)
Identifiable assets (period end)	109,835	58,096	60,017
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	0	0	0
Intersegment Eliminations | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	913	559	374
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	(393)	(265)	9
Intersegment Eliminations | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	(43)	(32)	(21)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	$ (477)	$ (262)	$ (362)