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Subsequent Event - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Subsequent Event [Line Items] |  |  |
Common stock, shares issued |  | 22,097,820 | 12,040,835
Scenario Forecast |  |  |
Subsequent Event [Line Items] |  |  |
Common stock, shares issued | 9,185,000 |  |
Sale of stock price per share | $ 5.75 |  |
Net proceeds | $ 3.5 |  |
Underwriting discounts and offering expenses | $ 49.3 |  |
Underwriters' overallotment option | Scenario Forecast |  |  |
Subsequent Event [Line Items] |  |  |
Common stock, shares issued | 485,000 |  |

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- Definition Underwriting discounts and offering expenses. + References No definition available. + Details
Name: | cbio_UnderwritingDiscountsAndOfferingExpenses
Namespace Prefix: | cbio_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_CommonStockSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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- Definition The cash inflow from the additional capital contribution to the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfCommonStock
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction. + References No definition available. + Details
Name: | us-gaap_SaleOfStockPricePerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_CounterpartyNameAxis=cbio_UnderwritersOverallotmentOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |