Stock-Based Compensation - Equity Incentive Plan Activity (Parenthetical) (Detail)	Sep. 30, 2013
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested during the period	160,740
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested during the period	379

Number of shares previously bested added to authorized for future issuance.

No definition available.

Name:	cbt_NumberOfSharesPreviouslyVestedAddedToAuthorizedForFutureIssuance
Namespace Prefix:	cbt_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant