Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Amount of paid and unpaid stock dividends declared and applicable to holders of share-based compensation, for example, but not limited to, non-vested shares, stock options, or restricted stock units.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Per share weighted average intrinsic value of equity-based compensation awards granted. Excludes stock and unit options.

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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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.

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- Definition

Number of allocated shares held by the Employee Stock Option Plan at balance sheet date. Allocated shares are shares that have been assigned to individual participant accounts based on a known formula.

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

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- Definition

Free cash flow compensation expense.

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- Definition

Number of additional employees to participate in plan.

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- Definition

Number of deferred equity units equivalent to one share of common stock.

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Share-Based Compensation Plans - Additional Information (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($) Employee $ / shares shares	Sep. 30, 2016 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional employees to participate in plan \| Employee	2
Shares held in employee stock option plan, allocated \| shares	82.1918
Shares issued and outstanding to LLC \| shares	55
Deferred equity unit share \| shares	0.0001
Weighted-average grant date intrinsic value of share awards \| $ / shares	$ 140.04	$ 107.13	$ 107.13
Non-cash compensation expense	$ 70	$ 23	$ 3
Free cash flow compensation expense	30
Dividend expense related to equity units	2
Unrecognized compensation costs	$ 34	2	7
Total compensation of unvested awards expected to be recognized, weighted average period	1 year
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-cash compensation expense		13	1
Non-Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-cash compensation expense		$ 10	$ 2
Matching Equity Units Vesting Years
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share awards vesting period	2 years
Deferred Equity Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares held in employee stock option plan, allocated \| shares	41.0959
Fair value of deferred equity units \| $ / shares	$ 241.75	$ 142.21	$ 135.00
Deferred Equity Units \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share awards vesting period	1 year
Deferred Equity Units \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share awards vesting period	7 years
Matching Equity Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares held in employee stock option plan, allocated \| shares	41.0959
Weighted-average grant date intrinsic value of share awards \| $ / shares	$ 90.06