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Derivative Instruments and Hedging Activities - Gains Losses on Freestanding Derivatives (Detail) - Other non-interest income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 20	$ 21	$ 36	$ 31
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	3	29	35	55
Interest rate contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	(5)	18	7	28
Interest rate contracts | Other interest rate exposures
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	17	(1)	1	(15)
Commodity contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	7	8	23	17
Foreign exchange contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	1	3	5	10
Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 0	$ (7)	$ 0	$ (9)

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+ References

No definition available.

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CC
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998890-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959

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