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Financial Instruments - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2017 USD ($)
Financial Instrument [Line Items] |
Material realized gains or losses on available-for-sale securities | $ 0
Maximum |
Financial Instrument [Line Items] |
Available for sale securities contractual maturities | 1 year

X
- Definition Available for sale securities contractual maturity. + References No definition available. + Details
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Namespace Prefix: | cbio_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financial instrument. + References No definition available. + Details
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Namespace Prefix: | cbio_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |