Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		$ 1,633	$ 1,609
Allocated provision for credit losses		150	148
Segment net interest income after provision		1,483	1,461
Noninterest income		1,180	1,171
Noninterest expense		1,686	2,102
Income before income taxes		977	530
Provision for income taxes		186	104
Net income		791	426
Identifiable assets (period end)		220,729	220,501	$ 221,642
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		837	842
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		464	406
FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		159	130
IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		26	23
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	147	208
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		1,633	1,609
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		886	876
Allocated provision for credit losses		122	129
Segment net interest income after provision		764	747
Noninterest income		339	331
Noninterest expense		673	673
Income before income taxes		430	405
Provision for income taxes		106	151
Net income		324	254
Identifiable assets (period end)		69,998	72,226
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		534	507
Allocated provision for credit losses		37	4
Segment net interest income after provision		497	503
Noninterest income		105	102
Noninterest expense		254	307
Income before income taxes		348	298
Provision for income taxes		78	103
Net income		270	195
Identifiable assets (period end)		56,435	55,328
Operating Segments | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		177	170
Allocated provision for credit losses		(5)	6
Segment net interest income after provision		182	164
Noninterest income		301	280
Noninterest expense		301	287
Income before income taxes		182	157
Provision for income taxes		38	48
Net income		144	109
Identifiable assets (period end)		29,766	28,227
Operating Segments | IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		20	19
Allocated provision for credit losses		1	2
Segment net interest income after provision		19	17
Noninterest income		439	463
Noninterest expense		375	400
Income before income taxes		83	80
Provision for income taxes		21	30
Net income		62	50
Identifiable assets (period end)		5,789	5,768
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	16	37
Allocated provision for credit losses	[1]	(5)	7
Segment net interest income after provision	[1]	21	30
Noninterest income	[1]	(4)	(5)
Noninterest expense	[1]	83	435
Income before income taxes	[1]	(66)	(410)
Provision for income taxes	[1]	(57)	(228)
Net income	[1]	(9)	(182)
Identifiable assets (period end)	[1]	58,741	58,952
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)		49	34
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		70	101
Intersegment Eliminations | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		18	40
Intersegment Eliminations | IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		(6)	(4)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	$ (131)	$ (171)

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