Amount of gain (loss) resulting from the difference between the acquisition price and the selling price or fair value of trading assets and trading liabilities, conducted separately from customer trading activities. Includes, but is not limited to, changes in fair value of trading assets and trading liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 35
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 220
-Section S99
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-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

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

Derivative Instruments and Other Financial Instruments Used For Hedging - Gain or (Loss) Recognized in Income on Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Trading Derivatives
Trading account activities	$ 34	$ (5)
Trading derivatives
Trading Derivatives
Trading account activities	(20)	80	$ (73)	$ 249
Trading derivatives \| Interest rate derivative contracts
Trading Derivatives
Trading account activities	(28)	64	(112)	194
Trading derivatives \| Equity contracts
Trading Derivatives
Trading account activities	(6)	5	1	23
Trading derivatives \| Foreign exchange derivative contracts
Trading Derivatives
Trading account activities	$ 14	$ 11	$ 38	$ 32