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Summary of Significant Accounting Polices - Grant Awards (Details) - USD ($) | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
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Summary of Significant Accounting Policies |  |  |
Grants from Muscular Dystrophy Association | $ 100,000 | $ 0 | $ 35,000

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- Definition Grants recorded as reduction in research and development expenses + References No definition available. + Details
Name: | catb_GrantOffsettingResearchAndDevelopmentExpenses
Namespace Prefix: | catb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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