Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Reclassification of terminated interest rate swaps to interest expense within the next 12 months	$ 6
Debt \| Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,800	$ 3,000
Foreign Exchange Contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	933	3,100
Currency Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	2,300
Fixed to Floating \| Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 1,200	$ 1,200

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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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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- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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