Noninterest Revenue and Noninterest Expense - Investment Banking Fees (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Noninterest revenue [Line Items]
Underwriting	$ 1,253	$ 1,247	$ 3,938	$ 3,978
Advisory	579	621	1,798	1,616
Total investment banking fees	1,832	1,868	5,736	5,594
Equity
Schedule of Noninterest revenue [Line Items]
Underwriting	417	302	1,342	1,105
Debt
Schedule of Noninterest revenue [Line Items]
Underwriting	$ 836	$ 945	$ 2,596	$ 2,873

Includes (1) underwriting revenue (the spread between the resale price received and the cost of the securities and related expenses) generated through the purchasing, distributing and reselling of new issues of securities (alternatively, could be a secondary offering of a large block of previously issued securities); and (2) fees earned for mergers, acquisitions, divestitures, restructurings, and other types of financial advisory services.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(b),(d))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration