Operating Segments - Reportable Segments (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		$ 6,535	$ 6,321	$ 5,592
Allocated provision for credit losses		547	572	428
Segment net interest income after provision		5,988	5,749	5,164
Noninterest income		4,782	4,472	4,019
Noninterest expense		7,444	6,721	6,266
Income (loss) before income taxes		3,326	3,500	2,917
Provision (benefit) for income taxes		911	1,058	794
Net income		2,415	2,442	2,123
Identifiable assets (period end)		221,642	219,276	209,947
CB-Retail
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		3,415	3,290	3,035
CB-Commercial
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		1,740	1,604	1,345
FS&CF
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		583	511	443
IH&PF
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		98	86	79
OT&C (1)
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)	[1]	699	830	690
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		3,564	3,405	2,916
Allocated provision for credit losses		501	475	365
Segment net interest income after provision		3,063	2,930	2,551
Noninterest income		1,404	1,354	1,342
Noninterest expense		2,725	2,469	2,357
Income (loss) before income taxes		1,742	1,815	1,536
Provision (benefit) for income taxes		650	686	588
Net income		1,092	1,129	948
Identifiable assets (period end)		71,093	74,642	71,027
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		2,119	2,008	1,669
Allocated provision for credit losses		69	(40)	1
Segment net interest income after provision		2,050	2,048	1,668
Noninterest income		423	392	390
Noninterest expense		1,198	1,302	1,153
Income (loss) before income taxes		1,275	1,138	905
Provision (benefit) for income taxes		441	403	324
Net income		834	735	581
Identifiable assets (period end)		56,563	55,035	51,231
Operating Segments | FS&CF
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		710	653	553
Allocated provision for credit losses		(15)	128	67
Segment net interest income after provision		725	525	486
Noninterest income		1,181	1,148	1,046
Noninterest expense		1,190	1,141	1,020
Income (loss) before income taxes		716	532	512
Provision (benefit) for income taxes		225	156	151
Net income		491	376	361
Identifiable assets (period end)		29,144	26,795	25,294
Operating Segments | IH&PF
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		77	67	63
Allocated provision for credit losses		4	3	4
Segment net interest income after provision		73	64	59
Noninterest income		1,777	1,731	1,611
Noninterest expense		1,590	1,525	1,371
Income (loss) before income taxes		260	270	299
Provision (benefit) for income taxes		99	104	105
Net income		161	166	194
Identifiable assets (period end)		6,024	5,943	4,998
Operating Segments | OT&C (1)
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)	[1]	65	188	391
Allocated provision for credit losses	[1]	(12)	6	(9)
Segment net interest income after provision	[1]	77	182	400
Noninterest income	[1]	(3)	(153)	(370)
Noninterest expense	[1]	741	284	365
Income (loss) before income taxes	[1]	(667)	(255)	(335)
Provision (benefit) for income taxes	[1]	(504)	(291)	(374)
Net income	[1]	(163)	36	39
Identifiable assets (period end)	[1]	58,818	56,861	57,397
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		0	0	0
Intersegment Eliminations | CB-Retail
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		149	115	(119)
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		379	404	324
Intersegment Eliminations | FS&CF
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		127	142	110
Intersegment Eliminations | IH&PF
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)		(21)	(19)	(16)
Intersegment Eliminations | OT&C (1)
Segment Reporting, Revenue Reconciling Items [Line Items]
Net interest income (expense)	[1]	$ (634)	$ (642)	$ (299)

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