Earnings Per Share - Earnings Per Share (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Income from continuing operations	$ 452	$ 410	$ 933	$ 843
Income (loss) from discontinued operations	77	(149)	103	(113)
Basic and diluted income available to common shareholders	$ (529)us-gaap_NetIncomeLoss	$ (261)us-gaap_NetIncomeLoss	$ (1,036)us-gaap_NetIncomeLoss	$ (730)us-gaap_NetIncomeLoss
Weighted Average Shares Outstanding
Basic weighted average shares outstanding	654.4	663.8	657.9	669.0
Effect of dilutive securities:
Stock options and unvested restricted stock	6.8	8.0	6.8	8.0
Diluted weighted average shares outstanding	661.2	671.8	664.7	677.0
Antidilutive Securities
Options to purchase common shares	0.5	0.2	0.4	0.2

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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- Definition

Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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Amount of income (loss) from a disposal group, net of income tax, reported as a separate component of income before extraordinary items after deduction or consideration of the amount allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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