Estimated amount of benefit resulting from favorable tax position.

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[Line Items] for Income Taxes, Additional Information [Table]

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Number of Months for Conclusion of Tax Examinations, Appellate Proceedings and or Tax Litigation

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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Amount of interest expense accrued for an underpayment of income taxes.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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The tax effect of gains or losses resulting from material events or transactions (that would not reasonably be expected to recur in the foreseeable future) that possesses a high degree of abnormality and are clearly unrelated to, or incidentally related to, the ordinary and typical activities of the entity.

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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Sep. 30, 2015
Income Taxes, Additional Information [Line Items]
Effective income tax rate	218.00%	22.00%	98.00%	20.00%
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%
Gross tax effected unrecognized tax benefits					$ 1,235
Amount of unrecognized tax benefits which may impact effective tax rate					1,180
Total net accrued interest, net of tax benefit					$ 41
Number of months for conclusion of tax exam, appeal or litigation	12 months
Estimated benefit to tax expense	$ 50
Restructuring Charges	229	$ 0	$ 229	$ 0
JAPAN
Income Taxes, Additional Information [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount				$ 17
2016 Restructuring Plan [Domain]
Income Taxes, Additional Information [Line Items]
Restructuring Charges	229
Restructuring Charges [Member]
Income Taxes, Additional Information [Line Items]
Unusual or Infrequent, Tax Effect	17
Automotive Experience
Income Taxes, Additional Information [Line Items]
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 780