Share-based Compensation - Awards Granted to Company Employees and Non-employee Directors Under the 2007 Equity Incentive Compensation Plan (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Non-qualified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	1,247,982
Weighted-Average Grant Date Fair Value (in dollars per share)	$ 29.37
Weighted-Average Exercise Price (in USD per share)	$ 182.50
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	2,189,944
Weighted-Average Grant Date Fair Value (in dollars per share)	$ 182.62
Performance-bases shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	470,128
Weighted-Average Grant Date Fair Value (in dollars per share)	$ 211.08
Equity Incentive Compensation Plan, 2007
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation cost	$ 111	$ 95

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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