Fair Value of Intangible Assets and Related Accumulated Amortization Expense (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Gross	$ 745	$ 656
Accumulated Amortization	(418)	(379)
Finite-Lived Intangible Assets, Net	327	277
Indefinite-lived Intangible Assets	27,521	26,957
Gross	28,266	27,613
Net	27,848	27,234
Customer relationships and reacquired rights
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets	23,437	22,873
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	438	351
Accumulated Amortization	(237)	(220)
Finite-Lived Intangible Assets, Net	201	131
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross	195	192
Accumulated Amortization	(93)	(80)
Finite-Lived Intangible Assets, Net	102	112
Reseller relationships
Finite-Lived Intangible Assets [Line Items]
Gross	95	95
Accumulated Amortization	(79)	(70)
Finite-Lived Intangible Assets, Net	16	25
Other
Finite-Lived Intangible Assets [Line Items]
Gross	17	18
Accumulated Amortization	(9)	(9)
Finite-Lived Intangible Assets, Net	$ 8	$ 9

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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

+ References

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount before accumulated amortization of intangible assets, excluding goodwill.

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph ((a)(1),(b))
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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