Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Feb. 28, 2017
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Amortization expense related to finite-lived intangible assets	$ 55	$ 56	$ 50
Impairment of indefinite-lived or finite-lived intangible assets	0	0	0
Payments to Acquire Businesses, Net of Cash Acquired	196	302	$ 9,082
Finite-lived Intangible Assets Acquired		$ 104
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		8 years
Goodwill	$ 15,194	$ 15,110		$ 181

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

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- Definition

Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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-Publisher FASB
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- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value.

+ References

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No definition available.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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