Expected production commencement year.

No definition available.

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- Definition

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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- Definition

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

No definition available.

+ Details

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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

+ Details

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6578-128477

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Balance Type:	credit
Period Type:	duration

- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=cbt_NSCCCarbonJiangsuCoLtdMember
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Acquisitions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended		3 Months Ended	6 Months Ended
	Sep. 30, 2018	Nov. 30, 2017	Mar. 31, 2019	Mar. 31, 2019
Tech Blend [Member]
Business Acquisition [Line Items]
Acquisition date		Nov. 30, 2017
Business acquisition, purchase price		$ 65
NSCC Carbon (Jiangsu) Co. Ltd [Member]
Business Acquisition [Line Items]
Acquisition date	Sep. 30, 2018
Expected Production commencement year	2021
Transition related costs			$ 1	$ 3
NSCC Carbon (Jiangsu) Co. Ltd [Member] \| Accounts Payable and Accrued Liabilities [Member]
Business Acquisition [Line Items]
Business acquisition, purchase price	$ 8