Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 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
Foreign Exchange Contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,500	$ 3,100
Fixed to Floating \| Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,200	$ 1,200
Euro Member Countries, Euro \| Debt \| Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	2,600
United Kingdom, Pounds \| Debt \| Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 327

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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+ 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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