Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		$ 1,696	$ 1,633
Allocated provision for credit losses		155	150
Segment net interest income after provision		1,541	1,483
Noninterest income		1,202	1,180
Noninterest expense		1,768	1,686
Income before income taxes		975	977
Provision for income taxes		177	186
Net income		798	791
Identifiable assets (period end)		227,683		$ 225,697
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		843	837
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		536	464
FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		189	159
IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		34	26
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	94	147
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		1,696	1,633
Allocated provision for credit losses		155	150
Segment net interest income after provision		1,541	1,483
Noninterest income		1,202	1,180
Noninterest expense		1,768	1,686
Income before income taxes		975	977
Provision for income taxes		177	186
Net income		798	791
Identifiable assets (period end)		227,683		220,729
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		952	885
Allocated provision for credit losses		130	122
Segment net interest income after provision		822	763
Noninterest income		322	340
Noninterest expense		645	660
Income before income taxes		499	443
Provision for income taxes		120	109
Net income		379	334
Identifiable assets (period end)		73,379		70,102
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		580	534
Allocated provision for credit losses		19	37
Segment net interest income after provision		561	497
Noninterest income		109	106
Noninterest expense		251	253
Income before income taxes		419	350
Provision for income taxes		91	79
Net income		328	271
Identifiable assets (period end)		56,702		56,438
Operating Segments | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		210	177
Allocated provision for credit losses		1	(5)
Segment net interest income after provision		209	182
Noninterest income		284	301
Noninterest expense		297	301
Income before income taxes		196	182
Provision for income taxes		40	38
Net income		156	144
Identifiable assets (period end)		33,141		29,766
Operating Segments | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		23	20
Allocated provision for credit losses		3	1
Segment net interest income after provision		20	19
Noninterest income		515	439
Noninterest expense		417	375
Income before income taxes		118	83
Provision for income taxes		30	21
Net income		88	62
Identifiable assets (period end)		6,376		5,789
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	(69)	17
Allocated provision for credit losses	[1]	2	(5)
Segment net interest income after provision	[1]	(71)	22
Noninterest income	[1]	(28)	(6)
Noninterest expense	[1]	158	97
Income before income taxes	[1]	(257)	(81)
Provision for income taxes	[1]	(104)	(61)
Net income	[1]	(153)	(20)
Identifiable assets (period end)	[1]	58,085		$ 58,634
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		0	0
Intersegment Eliminations | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		109	48
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		44	70
Intersegment Eliminations | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		21	18
Intersegment Eliminations | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		(11)	(6)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	$ (163)	$ (130)

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