Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		$ 1,690	$ 1,657	$ 3,386	$ 3,290
Allocated provision for credit losses		172	135	327	285
Segment net interest income after provision		1,518	1,522	3,059	3,005
Noninterest income		1,352	1,222	2,554	2,402
Noninterest expense		1,751	1,720	3,519	3,406
Income before income taxes		1,119	1,024	2,094	2,001
Provision for income taxes		234	202	411	388
Net income		885	822	1,683	1,613
Identifiable assets (period end)		230,872		230,872		$ 225,697
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		850	853	1,693	1,690
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		541	491	1,077	955
FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		197	169	386	328
IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		35	29	69	55
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	67	115	161	262
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		1,690	1,657	3,386	3,290
Allocated provision for credit losses		172	135	327	285
Segment net interest income after provision		1,518	1,522	3,059	3,005
Noninterest income		1,352	1,222	2,554	2,402
Noninterest expense		1,751	1,720	3,519	3,406
Income before income taxes		1,119	1,024	2,094	2,001
Provision for income taxes		234	202	411	388
Net income		885	822	1,683	1,613
Identifiable assets (period end)		230,872		230,872		222,681
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		976	922	1,928	1,807
Allocated provision for credit losses		123	110	253	232
Segment net interest income after provision		853	812	1,675	1,575
Noninterest income		387	355	709	695
Noninterest expense		654	659	1,299	1,319
Income before income taxes		586	508	1,085	951
Provision for income taxes		141	125	261	234
Net income		445	383	824	717
Identifiable assets (period end)		76,246		76,246		72,696
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		588	545	1,168	1,079
Allocated provision for credit losses		39	43	58	80
Segment net interest income after provision		549	502	1,110	999
Noninterest income		114	110	223	216
Noninterest expense		255	254	506	507
Income before income taxes		408	358	827	708
Provision for income taxes		89	80	180	159
Net income		319	278	647	549
Identifiable assets (period end)		56,450		56,450		57,011
Operating Segments | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		210	188	420	365
Allocated provision for credit losses		14	(4)	15	(9)
Segment net interest income after provision		196	192	405	374
Noninterest income		329	303	613	604
Noninterest expense		311	312	608	613
Income before income taxes		214	183	410	365
Provision for income taxes		45	38	85	76
Net income		169	145	325	289
Identifiable assets (period end)		33,595		33,595		30,446
Operating Segments | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		25	22	48	42
Allocated provision for credit losses		2	0	5	1
Segment net interest income after provision		23	22	43	41
Noninterest income		570	484	1,085	923
Noninterest expense		444	408	861	783
Income before income taxes		149	98	267	181
Provision for income taxes		38	25	68	46
Net income		111	73	199	135
Identifiable assets (period end)		7,162		7,162		6,321
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	(109)	(20)	(178)	(3)
Allocated provision for credit losses	[1]	(6)	(14)	(4)	(19)
Segment net interest income after provision	[1]	(103)	(6)	(174)	16
Noninterest income	[1]	(48)	(30)	(76)	(36)
Noninterest expense	[1]	87	87	245	184
Income before income taxes	[1]	(238)	(123)	(495)	(204)
Provision for income taxes	[1]	(79)	(66)	(183)	(127)
Net income	[1]	(159)	(57)	(312)	(77)
Identifiable assets (period end)	[1]	57,419		57,419		$ 56,207
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)		126	69	235	117
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		47	54	91	124
Intersegment Eliminations | FS&CF
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		13	19	34	37
Intersegment Eliminations | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)		(10)	(7)	(21)	(13)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net interest income (expense)	[1]	$ (176)	$ (135)	$ (339)	$ (265)

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