XML 21 R63.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Summary of Warrant Activity (Parenthetical) (Detail) - shares | 1 Months Ended | 12 Months Ended
--- | --- | ---
Nov. 30, 2018 | Dec. 31, 2019 | Dec. 31, 2018
Class Of Warrant Or Right [Line Items] |  |  |
Number of shares of warrants forfeited/cancelled |  | 2,337 | 6,095
Healthcare Ventures VIII |  |  |
Class Of Warrant Or Right [Line Items] |  |  |
Number of shares of warrants forfeited/cancelled | 1,845 |  |

X
- Definition Class of warrant or right, forfeited during period. + References No definition available. + Details
Name: | cbio_ClassOfWarrantOrRightForfeitedDuringPeriod
Namespace Prefix: | cbio_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ClassOfWarrantOrRightLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=cbio_HealthcareVenturesVIIIMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |