Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		$ 1,657	$ 1,635	$ 3,290	$ 3,244
Allocated provision for credit losses		135	135	285	283
Segment net interest income after provision		1,522	1,500	3,005	2,961
Noninterest income		1,222	1,220	2,402	2,391
Noninterest expense		1,720	1,742	3,406	3,844
Income before income taxes		1,024	978	2,001	1,508
Provision for income taxes		202	304	388	408
Net income		822	674	1,613	1,100
Identifiable assets (period end)		222,681		222,681		$ 221,642
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		853	853	1,690	1,695
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		491	430	955	836
FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		169	145	328	275
IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		29	25	55	48
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	115	182	262	390
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		1,657	1,635	3,290	3,244
Allocated provision for credit losses		135	135	285	283
Segment net interest income after provision		1,522	1,500	3,005	2,961
Noninterest income		1,222	1,220	2,402	2,391
Noninterest expense		1,720	1,742	3,406	3,844
Income before income taxes		1,024	978	2,001	1,508
Provision for income taxes		202	304	388	408
Net income		822	674	1,613	1,100
Identifiable assets (period end)		222,681	221,192	222,681	221,192
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		923	892	1,809	1,768
Allocated provision for credit losses		110	118	232	247
Segment net interest income after provision		813	774	1,577	1,521
Noninterest income		354	353	693	684
Noninterest expense		667	682	1,340	1,355
Income before income taxes		500	445	930	850
Provision for income taxes		123	166	229	317
Net income		377	279	701	533
Identifiable assets (period end)		72,577	72,791	72,577	72,791
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		545	525	1,079	1,032
Allocated provision for credit losses		42	46	79	50
Segment net interest income after provision		503	479	1,000	982
Noninterest income		108	109	213	211
Noninterest expense		254	320	508	627
Income before income taxes		357	268	705	566
Provision for income taxes		80	91	158	194
Net income		277	177	547	372
Identifiable assets (period end)		57,009	55,680	57,009	55,680
Operating Segments | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		188	183	365	353
Allocated provision for credit losses		(4)	(17)	(9)	(11)
Segment net interest income after provision		192	200	374	364
Noninterest income		303	297	604	577
Noninterest expense		312	300	613	587
Income before income taxes		183	197	365	354
Provision for income taxes		38	63	76	111
Net income		145	134	289	243
Identifiable assets (period end)		30,446	29,097	30,446	29,097
Operating Segments | IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		22	20	42	39
Allocated provision for credit losses		0	1	1	3
Segment net interest income after provision		22	19	41	36
Noninterest income		484	485	923	948
Noninterest expense		408	408	783	808
Income before income taxes		98	96	181	176
Provision for income taxes		25	36	46	66
Net income		73	60	135	110
Identifiable assets (period end)		6,321	6,275	6,321	6,275
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	(21)	15	(5)	52
Allocated provision for credit losses	[1]	(13)	(13)	(18)	(6)
Segment net interest income after provision	[1]	(8)	28	13	58
Noninterest income	[1]	(27)	(24)	(31)	(29)
Noninterest expense	[1]	79	32	162	467
Income before income taxes	[1]	(114)	(28)	(180)	(438)
Provision for income taxes	[1]	(64)	(52)	(121)	(280)
Net income	[1]	(50)	24	(59)	(158)
Identifiable assets (period end)	[1]	56,328	57,349	56,328	57,349
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)		70	39	119	73
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		54	95	124	196
Intersegment Eliminations | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		19	38	37	78
Intersegment Eliminations | IH&PF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		(7)	(5)	(13)	(9)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	$ (136)	$ (167)	$ (267)	$ (338)

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