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v3.10.0.1

Subsequent Event - Additional Information (Detail) | Jun. 30, 2018
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Carbon Black Operating Entity [Member] | Argentina [Member] |
Subsequent Event [Line Items] |
Ownership percentage | 100.00%

X
- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_ConsolidatedEntitiesAxis=cbt_CarbonBlackOperatingEntityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=country_AR
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |