Employee Benefit Plans - Fair Value of Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		$ 432	$ 555
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		153	249
Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		279	306
Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		22	22
Total Direct Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		22	22
Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		398	451
Total Investment Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		130	158
Total Investment Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		268	293
Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		11	13
Alternative Investments [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		11	13
Cash and Cash Equivalent Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	69
Cash and Cash Equivalent Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	69
U.S. Equity Securities [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		22	22
U.S. Equity Securities [Member] | Total Direct Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		22	22
Equity Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[1]	168	188
Equity Funds [Member] | Total Investment Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[1]	60	68
Equity Funds [Member] | Total Investment Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[1]	108	120
Fixed Income Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[2]	220	253
Fixed Income Funds [Member] | Total Investment Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[2]	70	90
Fixed Income Funds [Member] | Total Investment Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[2]	150	163
Real Estate [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[3]	9	9
Real Estate [Member] | Total Investment Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[3]	9	9
Common and Collective Investment Trust Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[4]		1
Common and Collective Investment Trust Funds [Member] | Total Investment Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[4]		1
Cash Equivalent Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1
Cash Equivalent Funds [Member] | Total Investment Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1
Insurance Contracts [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[5]	11	13
Insurance Contracts [Member] | Alternative Investments [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[5]	$ 11	$ 13

[1] The equity funds asset class includes funds that invest in U.S. equities as well as equity securities issued by companies incorporated, listed or domiciled in countries in developed and/or emerging markets. These companies may be in the small-, mid- or large-cap categories.

[2] The fixed income funds asset class includes investments in high quality funds. High quality fixed income funds primarily invest in low risk U.S. and non-U.S. government securities, investment-grade corporate bonds, mortgages and asset-backed securities. A significant portion of the fixed income funds include investment in long-term bond funds.

[3] The real estate funds asset class includes funds that primarily invest in entities which are principally engaged in the ownership, acquisition, development, financing, sale and/or management of income-producing real estate properties, both commercial and residential. These funds typically seek long-term growth of capital and current income that is above average relative to public equity funds.

[4] The investment objective of the portfolio of this common and collective investment trust is to achieve long-term, total return in excess of the MSCI World Index Benchmark by investing in equity securities of companies worldwide, emphasizing those with above-average potential for capital appreciation.

[5] Insurance contracts held by the Company’s non-U.S. plans are issued by well-known, highly rated insurance companies.