XML 75 R62.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Financial Information by Segment - Financial Information by Reportable Segment (Parenthetical) (Detail) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2016 | Mar. 31, 2015 | Mar. 31, 2016 | Mar. 31, 2015
Segment Reporting [Abstract] |  |  |  |
Percentage of sale of an equity method affiliate | 100.00% | 100.00% | 100.00% | 100.00%

X
- Definition Percentage of sale of equity method affiliates. + References No definition available. + Details
Name: | cbt_PercentageOfSaleOfEquityMethodAffiliates
Namespace Prefix: | cbt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_SegmentReportingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration