XML 74 R49.htm IDEA: XBRL DOCUMENT
v3.19.1

Fair Value of Financial Instruments - Schedule of Company's Classified Assets Measured at Fair Value on Recurring Basis (Detail) - Recurring - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Total assets | $ 111,742 | $ 61,291
U.S. Government Agency Securities and Treasuries |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Short-term investments | 3,972 |
Corporate debt securities |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Cash and Cash Equivalents |  | 11,405
Short-term investments | 107,505 | 28,585
Money market funds |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Cash and Cash Equivalents | 265 | 21,301
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Total assets | 2,252 | 21,301
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government Agency Securities and Treasuries |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Short-term investments | 1,987 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Cash and Cash Equivalents | 265 | 21,301
Significant Other Observable Inputs (Level 2) |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Total assets | 109,490 | 39,990
Significant Other Observable Inputs (Level 2) | U.S. Government Agency Securities and Treasuries |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Short-term investments | 1,985 |
Significant Other Observable Inputs (Level 2) | Corporate debt securities |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Cash and Cash Equivalents |  | 11,405
Short-term investments | 107,505 | 28,585
Significant Unobservable Inputs (Level 3) |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Total assets | 0 | 0
Significant Unobservable Inputs (Level 3) | U.S. Government Agency Securities and Treasuries |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Short-term investments | 0 |
Significant Unobservable Inputs (Level 3) | Corporate debt securities |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Cash and Cash Equivalents |  | 0
Short-term investments | 0 | 0
Significant Unobservable Inputs (Level 3) | Money market funds |  |
Fair Value Asset Measured On Recurring Basis [Line Items] |  |
Cash and Cash Equivalents | $ 0 | $ 0

X
- Definition Fair Value Asset Measured On Recurring Basis [Line Items] + References No definition available. + Details
Name: | sybx_FairValueAssetMeasuredOnRecurringBasisLineItems
Namespace Prefix: | sybx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
Name: | us-gaap_AssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
Name: | us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
Name: | us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USTreasuryAndGovernmentShorttermDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |