Benefit Plans - Fair Value Measurements of Foreign Plan Assets (Detail) - Pension Plans - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,932	$ 1,855	$ 1,732
Foreign Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	678	624
Foreign Plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	34
Foreign Plans | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	5
Foreign Plans | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	127	119
Foreign Plans | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	64	51
Foreign Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	256	228
Foreign Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28	13
Foreign Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26	17
Foreign Plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98	102
Foreign Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62	57
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	459	391
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	2
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	73
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	57	46
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	242	214
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28	13
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47	43
Foreign Plans | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	108	119
Foreign Plans | Significant Other Observable Inputs (Level 2) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	34
Foreign Plans | Significant Other Observable Inputs (Level 2) | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	3
Foreign Plans | Significant Other Observable Inputs (Level 2) | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45	46
Foreign Plans | Significant Other Observable Inputs (Level 2) | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	5
Foreign Plans | Significant Other Observable Inputs (Level 2) | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Other Observable Inputs (Level 2) | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	26	17
Foreign Plans | Significant Other Observable Inputs (Level 2) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Other Observable Inputs (Level 2) | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	14
Foreign Plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98	102
Foreign Plans | Significant Unobservable Inputs (Level 3) | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Foreign Plans | Significant Unobservable Inputs (Level 3) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98	102	$ 90
Foreign Plans | Significant Unobservable Inputs (Level 3) | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	14
Net Asset Value [Member] | Foreign Plans | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Government and agency-U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Government and agency-Foreign
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	14
Net Asset Value [Member] | Foreign Plans | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Net Asset Value [Member] | Foreign Plans | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0