Operating Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		$ 3,650	$ 1,696
Allocated provision for credit losses		893	155
Segment net interest income after provision		2,757	1,541
Noninterest income		1,961	1,202
Total noninterest expense		3,431	1,768
Income before income taxes		1,287	975
Provision for income taxes		224	177
Net income		1,063	798
Identifiable assets (period end)		506,229		$ 473,078
CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1,860	828
CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1,534	739
IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		36	34
OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	[1]	220	95
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		3,650	1,696
Allocated provision for credit losses		893	155
Segment net interest income after provision		2,757	1,541
Noninterest income		1,961	1,202
Total noninterest expense		3,431	1,768
Income before income taxes		1,287	975
Provision for income taxes		224	177
Net income		1,063	798
Identifiable assets (period end)		506,229	227,683
Operating Segments | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		2,248	1,021
Allocated provision for credit losses		437	131
Segment net interest income after provision		1,811	890
Noninterest income		1,072	507
Total noninterest expense		1,993	882
Income before income taxes		890	515
Provision for income taxes		209	125
Net income		681	390
Identifiable assets (period end)		168,356	75,873
Operating Segments | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		1,340	634
Allocated provision for credit losses		399	20
Segment net interest income after provision		941	614
Noninterest income		460	244
Total noninterest expense		886	315
Income before income taxes		515	543
Provision for income taxes		92	113
Net income		423	430
Identifiable assets (period end)		203,363	85,911
Operating Segments | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		25	23
Allocated provision for credit losses		1	3
Segment net interest income after provision		24	20
Noninterest income		557	515
Total noninterest expense		440	417
Income before income taxes		141	118
Provision for income taxes		36	30
Net income		105	88
Identifiable assets (period end)		7,009	6,376
Operating Segments | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	[1]	37	18
Allocated provision for credit losses	[1]	56	1
Segment net interest income after provision	[1]	(19)	17
Noninterest income	[1]	(128)	(64)
Total noninterest expense	[1]	112	154
Income before income taxes	[1]	(259)	(201)
Provision for income taxes	[1]	(113)	(91)
Net income	[1]	(146)	(110)
Identifiable assets (period end)		127,501	59,523
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		0	0
Intersegment Eliminations | CB-Retail
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		388	193
Intersegment Eliminations | CB-Commercial
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		(194)	(105)
Intersegment Eliminations | IH
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income		(11)	(11)
Intersegment Eliminations | OT&C
Segment Reporting, Revenue Reconciling Item [Line Items]
Net Interest Income	[1]	$ (183)	$ (77)

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