Business Segments Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	5
Lease, term of contract	10 years
Lease, extension term	5 years
Operating Segments [Member] \| RBWM [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the year ended December 31:		$ 7	$ (4)
Increase (decrease) in segment total assets at December 31:		(585)	(696)
Increase (decrease) in segment total deposits at December 31:		0	0
Operating Segments [Member] \| CMB [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the year ended December 31:		13	8
Increase (decrease) in segment total assets at December 31:		0	0
Increase (decrease) in segment total deposits at December 31:		0	0
Operating Segments [Member] \| GBM [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the year ended December 31:		(192)	(144)
Increase (decrease) in segment total assets at December 31:		(107,780)	(78,783)
Increase (decrease) in segment total deposits at December 31:		(6,989)	(5,011)
Operating Segments [Member] \| PB [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the year ended December 31:		5	4
Increase (decrease) in segment total assets at December 31:		0	0
Increase (decrease) in segment total deposits at December 31:		0	0
Operating Segments [Member] \| CC (as compared with previously reported Other) [Member]
Segment Reporting Information [Line Items]
Increase (decrease) in segment profit before tax during the year ended December 31:		167	136
Increase (decrease) in segment total assets at December 31:		108,365	79,479
Increase (decrease) in segment total deposits at December 31:		6,989	5,011
Group Reporting Basis, Other Operating Income [Member]
Segment Reporting Information [Line Items]
Gain (loss) from change in fair value of debt attributable to credit spread		$ (3)	$ 194

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- Definition

Group Reporting Basis, Increase (Decrease) to Segment Assets

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- Definition

Increase (Decrease) in Banking Deposits

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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Term of lessor's sales-type lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
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Term of lessor's sales-type lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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