Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

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-Publisher FASB
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-Section 50
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- Definition

Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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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.

+ References

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- Definition

Amount of cost for defined contribution plan.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
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Defined Benefit Plan Contribution Percent Of Compensation

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Pension and Other Postretirement Benefits - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value, assets, level 1 to level 2 transfers, amount		$ 0
Defined contribution plan, personnel costs		121,000,000	$ 93,000,000	$ 58,000,000
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Cash balance formula contributions, rate of eligible compensation	6.00%
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value, assets, level 1 to level 2 transfers, amount		$ 0	$ 0
Equity securities \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations		65.00%
Equity securities \| Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		15.00%
Actual plan asset allocations		14.00%
Fixed income securities \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations		33.00%
Fixed income securities \| Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations		48.00%
Other security investments \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations		2.00%
Other security investments \| Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		45.00%
Actual plan asset allocations		38.00%
Interest and Inflation Hedging Assets \| Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		40.00%
Minimum \| Equity securities \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		50.00%
Minimum \| Fixed income securities \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		25.00%
Maximum \| Equity securities \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		80.00%
Maximum \| Fixed income securities \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		35.00%
Maximum \| Other security investments \| U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation, percentage		7.00%