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Financial Information by Segment - Additional Information (Detail)
 1 Months Ended 3 Months Ended
Dec. 31, 2014
Segments
Dec. 31, 2014
Segment
Segment Reporting Information [Line Items]    
Number of aggregated business segment 4us-gaap_NumberOfReportableSegments 4us-gaap_NumberOfReportableSegments
Performance Chemicals [Member]    
Segment Reporting Information [Line Items]    
Number of aggregated business segment   1us-gaap_NumberOfReportableSegments
/ us-gaap_StatementBusinessSegmentsAxis
= cbt_PerformanceChemicalsMember
Number of business activity   2cbt_NumberOfBusinessActivity
/ us-gaap_StatementBusinessSegmentsAxis
= cbt_PerformanceChemicalsMember