Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		$ 1,687	$ 1,647	$ 4,977	$ 4,891
Allocated provision for credit losses		135	126	420	409
Segment net interest income after provision		1,552	1,521	4,557	4,482
Noninterest income		1,239	1,166	3,641	3,557
Noninterest expense		1,742	1,745	5,148	5,589
Income before income taxes		1,049	942	3,050	2,450
Provision for income taxes		210	294	598	702
Net income		839	648	2,452	1,748
Identifiable assets (period end)		222,885		222,885		$ 221,642
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		880	863	2,570	2,558
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		513	451	1,468	1,287
FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		171	154	499	429
IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		32	25	87	73
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	91	154	353	544
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		1,687	1,647	4,977	4,891
Allocated provision for credit losses		135	126	420	409
Segment net interest income after provision		1,552	1,521	4,557	4,482
Noninterest income		1,239	1,166	3,641	3,557
Noninterest expense		1,742	1,745	5,148	5,589
Income before income taxes		1,049	942	3,050	2,450
Provision for income taxes		210	294	598	702
Net income		839	648	2,452	1,748
Identifiable assets (period end)		222,885	220,340	222,885	220,340
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		957	901	2,766	2,669
Allocated provision for credit losses		121	116	353	363
Segment net interest income after provision		836	785	2,413	2,306
Noninterest income		346	362	1,039	1,046
Noninterest expense		664	675	2,004	2,030
Income before income taxes		518	472	1,448	1,322
Provision for income taxes		127	176	356	493
Net income		391	296	1,092	829
Identifiable assets (period end)		72,933	71,393	72,933	71,393
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		571	541	1,650	1,573
Allocated provision for credit losses		18	0	97	50
Segment net interest income after provision		553	541	1,553	1,523
Noninterest income		109	107	322	318
Noninterest expense		263	295	771	922
Income before income taxes		399	353	1,104	919
Provision for income taxes		89	123	247	317
Net income		310	230	857	602
Identifiable assets (period end)		56,685	55,639	56,685	55,639
Operating Segments | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		197	178	562	531
Allocated provision for credit losses		5	9	(4)	(2)
Segment net interest income after provision		192	169	566	533
Noninterest income		308	289	912	866
Noninterest expense		312	296	925	883
Income before income taxes		188	162	553	516
Provision for income taxes		39	50	115	161
Net income		149	112	438	355
Identifiable assets (period end)		30,586	29,006	30,586	29,006
Operating Segments | IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		23	19	65	58
Allocated provision for credit losses		1	1	2	4
Segment net interest income after provision		22	18	63	54
Noninterest income		452	401	1,375	1,349
Noninterest expense		416	389	1,199	1,197
Income before income taxes		58	30	239	206
Provision for income taxes		15	12	61	78
Net income		43	18	178	128
Identifiable assets (period end)		6,455	5,985	6,455	5,985
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	(61)	8	(66)	60
Allocated provision for credit losses	[1]	(10)	0	(28)	(6)
Segment net interest income after provision	[1]	(51)	8	(38)	66
Noninterest income	[1]	24	7	(7)	(22)
Noninterest expense	[1]	87	90	249	557
Income before income taxes	[1]	(114)	(75)	(294)	(513)
Provision for income taxes	[1]	(60)	(67)	(181)	(347)
Net income	[1]	(54)	(8)	(113)	(166)
Identifiable assets (period end)	[1]	56,226	58,317	56,226	58,317
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		0	0	0	0
Intersegment Eliminations | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		77	38	196	111
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		58	90	182	286
Intersegment Eliminations | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		26	24	63	102
Intersegment Eliminations | IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		(9)	(6)	(22)	(15)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	$ (152)	$ (146)	$ (419)	$ (484)

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