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Basis of Presentation - Additional Information (Detail)
 1 Months Ended 3 Months Ended
Dec. 31, 2014
Segments
Dec. 31, 2014
Segment
Nov. 30, 2013
Basis Of Presentation [Line Items]      
Number of reporting segments 4us-gaap_NumberOfReportableSegments 4us-gaap_NumberOfReportableSegments  
NHUMO [Member]      
Basis Of Presentation [Line Items]      
Percentage acquisition     60.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
/ us-gaap_BusinessAcquisitionAxis
= cbt_NhumoMember
Ownership percentage prior to acquisition     40.00%us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
/ us-gaap_BusinessAcquisitionAxis
= cbt_NhumoMember