Fair Value of Intangible Assets and Related Accumulated Amortization Expense (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross	$ 763	$ 745
Accumulated Amortization	(473)	(418)
Finite-Lived Intangible Assets, Net	290	327
Indefinite-lived Intangible Assets	27,268	27,521
Gross	28,031	28,266
Net	27,558	27,848
Customer relationships and reacquired rights
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets	23,184	23,437
Visa trade name
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets	4,084	4,084
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross	452	438
Accumulated Amortization	(274)	(237)
Finite-Lived Intangible Assets, Net	178	201
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross	199	195
Accumulated Amortization	(106)	(93)
Finite-Lived Intangible Assets, Net	93	102
Reseller relationships
Finite-Lived Intangible Assets [Line Items]
Gross	95	95
Accumulated Amortization	(82)	(79)
Finite-Lived Intangible Assets, Net	13	16
Other
Finite-Lived Intangible Assets [Line Items]
Gross	17	17
Accumulated Amortization	(11)	(9)
Finite-Lived Intangible Assets, Net	$ 6	$ 8

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
-SubTopic 340
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6473545&loc=d3e61844-108004

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- Definition

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.

+ References

No definition available.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

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- Definition

Amount before accumulated amortization of intangible assets, excluding goodwill.

+ References

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- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

+ References

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